Glacial extent variability during last glacial period? Does anyone know an online source to illustrate glacial extent variability during last ice age, ca 120 ka BP to 10 ka BP? Most sources seem to concentrate only on the maximum, but apparently, there was quite a lot of variability. I'm mostly interested in Europe.
Thanks for any hints.

This map should address at least part of your question

The here documented GIS map and dataset contains a collection of Last
Glacial Maximum (LGM, ~21k yBP) paleoenvironmental data. It is the
first result of a project that aims to acquire, produce and publish
GIS datasets from non-GIS based sources such as analogous maps,
textual informations or figures of scientific publications for
prehistoric time slices. In combination with modelling results and
already available GIS-datasets related to the mentioned time frame, it
should enable other researchers and members from other projects to use
the maps in their work, properly cited and referenced. The map shows
LGM land ice sheets, paleo-stream networks and inland water in Europe,
a sea-level adapted (-120m) land mass and a Köppen-Geiger climate
classification derived from climate model data.

I know this is more broadly a field of active study and there is a relatively new method of analyzing cosmogenic nuclides to determine for what duration a surface has been exposed to cosmic radiation.
Broadly how this works is that surfaces exposed to cosmic radiation start to develop an isotopic signature, to the degree that you can tell how long a boulder has been exposed to the open sky (within a margin of error).
Joerg M. Schaefer of Lamont-Doherty Earth Observatory explains in Glacial Landscape (Cosmogenic Nuclide) in the Encyclopedia of Scientific Dating Methods:

High-sensitivity cosmogenic nuclide techniques applied to the moraine
record now afford for precise reconstruction of past glacier
fluctuations with centennial resolution and on a time scale ranging
from decades to beyond 100,000 years. It has been a long-standing
dream of geologists and climate scientists alike to precisely map land
ice change during the last ice age through the deglaciation period and
into the current interglacial, referred to as the Holocene.


Why is there a line of volcanoes along the northwest coast of North America? Mount Hood in Oregon is a dormant volcano, and in Washington Mount St. Helens and Mt. Ranier are both active volcanoes.  What causes this line of volcanoes running parallel to the coastline along the northwest coast of North America?

The Cascades (the volcanic range that Mt. St. Helens and Mt. Ranier are a part of) are "arc volcanoes" (a.k.a. "a volcanic arc", etc).

Volcanic arcs form at a regular distance (and fairly regular spacing) behind subduction zones.  Subduction zones are areas where dense oceanic crust dives beneath more buoyant crust (either younger oceanic crust or continental crust).

The down-going oceanic plate begins to generate fluids due to metamorphic reactions that occur at a particular pressure and temperature.  These fluids cause partial melting of the mantle above the down-going slab.  (Contrary to what's often taught, the oceanic crust itself doesn't melt at this point - it's the mantle above it that does.)

This causes arc volcanoes to form at the surface at approximately where the down-going oceanic slab reaches ~100km depth (I may be mis-remembering the exact number).

However, there's an interesting story with the Cascades, the San Andreas Fault, and the Sierra Nevada.

Basically, Sierras are the old volcanic arc before an oceanic spreading ridge tried to subduct off the coast of California. (Search for the Farallon plate.) The ridge was too buoyant to subduct, so subduction stopped, shutting off the supply of magma to the volcanic arc.  Because the motion of the Pacific Plate (on the other side of the spreading ridge that tried to subduct) was roughly parallel to the margin of North America, a strike slip boundary formed instead: The San Andreas Fault.  Northward, there's still a remnant of the Farallon plate that's subducting beneath Northern CA, OR, WA, and BC.  Therefore, the Cascades are still active arc volcanoes, while the Sierras are just the "roots" of the old arc.


Desalination and Weather Impact? I have a question I've always been curious about regarding the topic.

As I understand it, the desalination process is that they take the salt water, create usable water from it and then salt sludge is pumped back out into the ocean.  When I've read about it an issue from this seems to be that the waste is bad to the ecosystem they pump it back into plus that extra salt can't be that good for the ocean as a whole and its inhabitants.  I understand that one plant might not be that much of an impact on the ocean as a whole but if it became more standard and over 50yrs+, especially with the changing climate and droughts maybe it would and there are greater ecological issues.

My question is:
Why can't they just pump the salt water into a designated area in the desert?

I live in California and we have plenty of desert and every time I head out toward Las Vegas or travel up north I think about this.

Why couldn't some chunk of land be allocated where raw salt water can be pumped into and then let it evaporate?  Wouldn't that just generate more rain which, at least in the winter, create more snow pack in the mountains and help create drinking water more naturally?  The salt and stuff left behind could just stay there and become a salt flat.  At a minimum couldn't they process the water and then pump the sludge into the desert (the remaining water would still evaporate) and it seems to me that would be a better solution than putting it back into the ocean for it to have more salt.

If it could be done on a reasonable scale, maybe some land that was once unusable could be terraformed to forest which would help with the climate, pull carbon out of the air, and on a 5 or 10 year cycle the trees can be cut down made into mulch and then new ones planted...  Not the salt water or land where the salt is left but additional land allocation for this (we do have a LOT of desert) and I know sand would need to be cultivated but we also have a lot of cows and organic material we can use to help convert the sand into more usable soil.

Running some pipes from a coast inland while posing some logistical challenge doesn't seem unreasonable to me.  Better than oil pipelines...

Thanks for the responses

Your first question, regarding salt pollution requires a back-of-an-envelope calculation. At present, about 4% of the global population relies, either wholly or in part, on desalinated water. Because this is energy intensive, it is also expensive, so such water users are parsimonious, using about 1% of the global domestic water supply. But let us, for the sake of argument, assume that the desalinated option really takes off at some time in the future, perhaps by means of less energy intensive 'forward osmosis'. We will assume that 10% of the current population (7.4 billion people) may eventually use desalinated water, yielding a daily delivery of bitterns with 2.45 x 10^^9 tonnes of salt. Compare this to the 1,5 x 10^^17 tonnes of salt already in the ocean - the salt return would be 0.0000016% of what is already in the sea. Moreover, even this trivial amount would be diluted by the hydrological cycle, because the water that is drunk, used for washing, etc, ultimately returns to the sea.

But you ask whether the local concentrated saline return would be harmful to the environment? Consider Adelaide, in South Australia, which boasts the largest desalination plant in the southern hemisphere. Very detailed studies, by both computer modelling and direct observation, show that the dispersion of the saline plume reaches concentrations undetectable against the background salinity, within a few hundred metres of the outflow. It certainly hasn't impacted the local marine ecology at all - and the South Australians are very particular about environmental issues!

Again, consider the greatest concentration of desalination plants in the world, in the Arabian Gulf. This shallow-water (<50 metres) Gulf has high natural rates of evaporation, which raises the salinity from the normal 3.6% to about 4.1%. This change is orders of magnitude more than can be attributed to the salinity change from all the desalination plants combined. The ecology and biodiversity of the Gulf is still rich, and not at all affected by local bitterns effluent. Climate change will intensify evaporation, which is much more of a worry than 'desal' plants.

As to your second question about changing the climate and increasing rainfall by pumping bitterns into the desert, there is a massive problem with that. As the salinity increases by evaporation, the vapour pressure at the lake surface decreases, which suppresses further evaporation. Since we would be dealing with hyper-saline brines to start with, we would rapidly approach an equilibrium in which the massively decreased evaporation would equal the natural deliquescence of the salt. In fact, evaporation would win, but only slightly. The loss of moisture to the atmosphere would be barely noticeable, and not sufficient to terra-form the down-wind area.

I suggest that the impacts of global warming will massively eclipse any trivial changes brought about by evaporation basins. If you don't believe me, I suggest you get some hydrologic and geochemical textbooks, and do some mass-balance calculations of your own.


What caused the Carbon Dioxide Variations observed in the 800,000-year polar ice record? I have seen several graphs showing the prehistoric temperatures and CO2 concentrations derived from ice-core data.    My understanding is that CO2 and temperature correlate.  I assume that Milankovich Cycles are what caused the variations observed in temperature in the ice record, but what specifically caused the CO2 to fluctuate?

This article investigates the ocean's dissolved carbon content (ocean reservoir) and the seafloor's methane hydrates ("methane ice") as a source of CO2 fluctuations in ice cores. They discuss three ways the ocean may release CO2.

through physics (changes in temperature and ocean currents)
biologically or chemically
through general climate changes

Hope this helps.


How do quartz veins form? Is there an association with thrust fault or dormant volcanos and quartz veins? Where are quartz veins likely to occur in nature and how are the formed?

Is it possible to identify these veins from satellite images.

The formation of quartz veins needs fluids enriched in Si. Usually Si dissolves somewhere in neighbouring formations, gets transported by fluids and precipitates where the fluid pressure is low (the fluids Si-saturation capacity decreases with decreasing fluid pressure).
Fluid pressure is usually involved in rock fracturing. When it builts-up, it can fracture the rock. Thereby generated fractures, in turn, accomodate void space, hence the fluid pressure drops and Si precipitates from the fluid to form veins. These veins reseal and restrengthen the rock, which can again lead to a renewed fluid pressure built-up. This process is known as crack-seal vein formation.

Usually, crack-seal vein formation happens progressively, which is a very nice thing: Studying vein internal mineral structures gives evidence to past stress regime conditions. These evidences can help unraveling the evolution of tectonic structures, such as mountain formations or fault systems.

Quartz veins are very common, they need a source of disolvable Si, which is a really abundant element. In carbonate rocks, calcite veins are more common. The crack-seal principle applies for them just the same.

Yes, you can see veins in satelite pictures! Have a look here: OMAN (These are calcite veins standing out against a darker limestone).

Hope this helps,
Ben

P.S.: You might want to have a look at my thesis on (calcite) vein-networks in Oman: LINK.


Why would CaO be more finely spread than K2O in Granodiorite? I recently interpreted some XRF data on samples of a granodiorite which were classified under three different types of physical characteristics: very little, mild and significant levels of weathering. I plotted ratios between $Al_2O_3$ for $CaO$ and $K_2O$ and noticed $CaO$ had a much lower correlation coefficient, i.e., it was more clumped. I know it's about which of these elements go into clay compounds but I need a bit more help understanding.

Data

I would suggest that there is a combination of effects here:

Potassium(K) compounds are usually more soluble than their Calcium(Ca) equivalents, and often at much lower temperatures. For example $CaCO_3$ is in considered insoluble in even boiling water, while $K_2CO_3$ is fully soluble at room temperature. Potassium can therefore migrate more easily during weathering involving water infiltration than can Calcium leading to a finer distribution. The "clumps" of $CaO$ represent more closely it's original crystal positions while the finely divided $K_2O$ has migrated farther dispersing it through the samples.

The clumping in less weathered samples could be purely an artifact of the nature of the parent rock Granodiorite is relatively enriched in Calcium over Potassium so Calcium shows up as large concentrations while Potassium is more thinly spread through the samples.


What would it be like to live in an ice age? If you were born in the most recent ice age, how different would your life be compared to how you live it today? Furthermore, if humans currently lived in an ice age, how would it affect life today?

It depends where, the continental landmasses at higher latitudes would be covered by massive ice sheets. Therefore the life in the sections of the US and Europe that are close to the Ice sheets would have conditions similar to what is life in Greenland today. The map would look like this:

(Image taken from planetaryvisions.com)

And the summers would be more mellow than what you are used to. Mean global temperatures would be much lower but at tropical latitudes there would still be warm weather. That means that the temperature gradient between the equator and the poles would be larger, leading to quicker climatic transitions as you travel North or South, and also leading to stronger winds and probably more powerful storms.

Also the sea level would be about 120 meters lower than today, exposing many areas that are now underwater, some of them massive, like the Sunda land bridge (see map in the Indonesia area), many islands would be connected to the continents, like Tasmania to Australia and Sirilanka to India.
England would be connected to Europe and the Persian gulf would be dry, as well as the Yellow sea. New Zealand would be just one big island, and hundreds of islands that are now underwater would poke the oceans.
Using ETOPO1 I've put together a fairly high resolution image of the world showing all the land that would be exposed if the sea level today drops 120m (as it did on the last ice age). You can see it here.

Furthermore, the Pacific and the Atlantic would be completely isolated from each other for navigation proposes, as the Magellan strait and Drake passage would be blocked by ice and the Panama canal would be a nearly impossible feat, with the sea level ~120 m lower than today. So probably, train transport would be much more important to carry goods across the Americas.

The Suez canal would not exist either, and navigation around the Good hope cape at the southern tip of Africa would be constantly threatened and perhaps blocked by icebergs, so most transport between the Indian and Atlantic ocean would be by land too.

The sea ice would be in contact with the tropical gyros, meaning that massive floating ice islands would be seen even at the Ecuador, and icebergs would be all around the oceans.

All that would mean that all the empires that rose from naval power (England, Portugal, Spain) would might not existed, then, maybe Asian powers would rule the world undisputed, and the colonization/invasion of many territories would have never happen or at least would have been delayed, leading to a completely different world distribution and organization.

Another interesting change, would be the scarcity of shallow seas compared to today. The drop in total surface area for a given elevation below current sea level becomes stepper once the sea level drops more than 60 m. Therefore, the sea depth would increase quicker as you go seaward from an "ice age seashore". This would lead also to a drop in coastal water productivity (opposite to what is believed to have happened in the Cretaceous, with high sea level and abundant shallow seas).

Also the day would be about one and a half minutes longer, meaning that the year would have only 364 days.

The change in day length would lead to calendar changes. Currently, a year have 365.2422 days, that is approximated in our calendar to 365.2425, with the fraction part divided as

0.2425 = 0.25-0.01+0.0025

The +0.25 is compensated by adding one day every four years, that is a leap year
The -0.01 is compensated by skipping one leap year every 100 years
And the +0.0025 is compensated by not skipping one leap year every 400 years.

That's how our calendar works today.

Now, if we assume that the figure of a day 1.5 minutes longer is precise, one year would have 364.8621 days, and the fractional part would probably be approximated to 0.8620, and perhaps divided as

0.8620 = 0.80 + 0.05 +0.02 -0.0080

So the calendar rule would perhaps be like

+0.80 compensated by adding one day every year except every 5 years
+0.05 compensated by skipping the above rule exception every 20 years and add a day anyways
+0.02 compensated by skipping the exception to the first rule once more every 50 years.
-0.0080 compensated by not adding an extra day every 125 years

Or something like that, many other arrangements could be imagined. But at the end, a typical year would still have 365 days, but the leap years would have one day less instead of one extra day.


Open source seismic refraction processing What I am in search of is an open source tool to pick first arrivals, plot travel-time curves, and perform simple velocity modeling.

I am experimenting with seismic refraction to identify shallow subsurface interfaces. This includes the water table in a sand channel and the sand/bedrock contact.

I have a 24 channel Seistronix RAS-24 for field acquisition. This includes a field computer with software to set geometry, run the survey, and record data to various .seg formats.

What I do not have is a reliable program to process and model my data. Thus far I have been evaluating seismograms in the field and calculating depths by hand with the text book equations.

I am open to any freely available software solution that would allow me to interpret and visualize my field data. This includes python or matlab based packages.

Are there any open source and community supported seismic refraction processing tools available?

There are several references to refraction tools in the Wikipedia page for free geophysics software:

https://en.wikipedia.org/wiki/Comparison_of_free_geophysics_software


Aligator or Dinosaur Fossil skin type rock The more I looked at this stone and touched it, the more this thing looked like it was wrapped in some kind of reptile skin. It may just be a random rock. More photos if needed. Does this look like something you may have seen before?

It's mainly green/yellow in color except for the pattern on the rock. The skin like pattern is a very dark color, almost black. It's a very hard rock, not breakable. It seems to weigh what it should. Not too heavy or light. We were looking for fossils in a sand bar that was in the shallows of the Bogue Chitto River in Mt. Herman Louisiana. This river is fed by the Mississippi River. We found it a couple weeks after some severe weather. Rivers had gotten pretty high & were at flood stage. Once they receeded, we went on our adventure. We found several other fossils of shells, and small centipede looking fossils. We only picked this one up because it reminded us of an alligator toe.

I agree with commentator @John, this is a fossil coral.  The coral animal (the polyp) builds a column, and as it ages it closes off the bottom and extends the upper lip.  In some of the views you see the column structure.  In others you see the arrangement of polyps.  It looks like the cells of the coral are filled in with calcite, which probably made the fossil harder than the surrounding rock.  When the rock weathered the fossil coral broke apart.  It looks like this piece is a rounded pebble from a stream bed.  Or possibly the coral broke up and was rounded by wave action.

Compare this picture http://www.fossilmuseum.net/fossil-art/cnidaria/tabulatecorals.jpg


Mixing equation for confluence of two rivers How can I calculate the final concentration of two ions in a river after the confluence of two rivers?

River 1 flows at $\small\sf{7000\ L/s}$, contains $\small\sf{500\ mg/L\ Mg,\ 1.1\
   g/L\ Ca}$
River 2 flows at $\small\sf{11\ m^3/s}$, contains $\small\sf{0.34\ g/L\ Mg,\ 200\
   mg/L\ Ca}$

How do I find Mg and Ca concentrations in River 3, after the joining of Rivers 1 and 2?

You have to use mass weighted averaging to calculate the final concentrations of elements. The equation for your situation would be:

$\sf\bar{q}\ =\ \dfrac{m_1.q_1\ +\ m_2.q_2}{m_1\ +\ m_2}\ =\ \dfrac{\rho_1.v_1.q_1\ +\ \rho_2.v_2.q_2}{\rho_1.v_1\ +\ \rho_2.v_2}$

where:

$\small\sf m$ is the mass flow rate
$\small\sf v$ is the volume flow rate
$\small\rho$ is the density of water
$\small\sf q$ is the quantity/concentration of the element

Every second, $\small\sf{7000\ L}$ of water flows from River 1 into River 3. Similarly, $\small\sf{11\ m^3}$ of water flows from River 2 into River 3. The combined inflow into River 3 is $\small\sf{18\ m^3}$ every second.

Assuming the density of water in both inflowing rivers is the same, volume of water can be used instead of mass; if not then the density of water for each river needs to be used.

Assuming the water density of both rivers is the same, convert all to units SI units and the average concentration of Mg in River 3 is,

$\sf{\dfrac{7(0.5) + 11(0.34)}{(7 + 11)}}$ = $\sf{0.402\ g/L\ Mg}$

I'll let you do the calculation for Ca.


I found this huge rock crystal by the river have no idea what it is? ![crystal rock yelowish to red yellow to orange has 3 layers of crystal
)

Your rock is probably a piece of a sedimentary concretion.  I have collected rocks that look very similar from western South Dakota.  The yellow crystals are most likely calcite.  The dark brown colored material is also probably calcite and but might be barite.

Acid testing using HCL should confirm if the yellow and brown area are calcite.
It will probably be difficult to perform an accurate specific gravity measurement for the rock.  My experience is that concretions are commonly quite dense (denser than calcite/dolomite) due to presence of denser minerals such as ankerite, dolomite, barite, celestite, fluorite, marcasite, pyite, sphalerite, siderite, wurzite, and galena as microscopic inclusions hidden within the matrix material.

Concretions definition from wikipedia.


What is an 'obstacle vista diagram'? Currently I do some research about SODAR and at this paper, the author wrote (p. 1502f):

  A site should be relatively clear of obstacles that could act as
  potential fixed-echo reflectors. If that is not possible, then it is
  therefore important to construct an obstacle vista diagram prior to
  sodar installation  which  identifies  the  direction  and  height
  of potential reflectors in relation to the sodar (Baxter, 1994, 1996).
  This diagram can be used after some data have been collected to assess
  whether or not reflections are of concern at some sodar height ranges.

Unfortunately, I can't find any access to the referenced literature and google wasn't helpful either. So, what is an obstacle vista diagram and how to construct it?

Just taking a guess from the context, I think it could be a "view shed", the term used in GIS (Geographic Information Systems) to refer to a visibility analysis. In other words, it is a calculation that determines which areas of a given terrain would be visible from a specific point.

It is used to know, for example, what would be the coverage of a radio transmitter on a given location, or from which areas would a lighthouse not be visible, etc. To calculate such diagram you need a DEM (Digital Elevation Model) of the area.

To give you an example I just loaded a DEM and run a calculation (using Global Mapper) of the areas visible from a 20 meters tall tower in the top of a specific hill, and within a 40 km radius. And this is how the results looks like:

Where the red shading show the areas that are visible from the tower. The rest of the terrain would be hidden behind topographic obstacles.


What geological events could cause a Volcanic Explosivity Index (VEI) level 9 eruption? The Volcanic Explosivity Index (VEI) is a way of measuring the relative explosiveness of volcanic eruptions, allowing for comparisons between volcanoes.   According to the USGS Volcanic Hazards page,

  The VEI uses several factors to assign a number, including volume of erupted pyroclastic material (for example, ashfall, pyroclastic flows, and other ejecta), height of eruption column, duration in hours, and qualitative descriptive terms.

Measurements of the ejecta allows an estimate of the VEI of long past eruptions to be made.

As can be seen in the following scale (USGS):

The USGS also state that each interval representing

  an increase of about a factor of 10 in the volume of erupted tephra.

Some eruptions are massive, the largest according to Geology.com was Wah Wah Springs about 30 million years ago, releasing somewhere around 5500 cubic kilometre - this is classified as a VEI 8.

Given the scale increases by a factor of 10x the amount of ejecta, my question is, what are the geological events or precursors that would result in a VEI level 9 eruption (i.e. volume of ejecta greater than 10,000 cubic kilometres)?

A fairly recent article by the Geological Society of America: Arc magmatism, calderas, and supervolcanoes (de Silva, 2008) states that VEI-8 (or volcanoes that release 1000 km$^3$ of tephra) are classed as being supervolcanic - and something that we have not witnessed in recorded history.  Specifically, the author describes VEI-8 (and greater) eruptions to be the result of 'supervolcanic caldera forming event flare ups'.

However, de Silva characterises the volcanism for this type of event as requiring a thermal and physical environment that can support storage and the mantle basaltic flux for the production of massive silicic magma.

As according to several authors including Siebert et al. (book: Volcanoes of the World), there is no evidence of a VEI-9 eruption found yet, the best way to think about this question is to imagine a majorly upscaled version of a VEI-8 supervolcano, such as Toba or Yellowstone.

So, the geological events for a hypothesised VEI-9 eruption would need (adapted from de Silva):

the development of a magma chamber that could support the magma that would be fragmented to produce at least 10,000+ km$^3$ of volcanic ash - this would probably result in major uplift in the area, with faulting around the edges.
flare up conditions that are the result of elevated power input from the mantle resulting in a major shift to an increase in silicic magma productivity - this could include a massive array of geysers (if water were present), heating of the ground, possibly widespread gas vents.
the thermomechanical evolution of the crust through a positive feedback between mantle power, mantle production, heat advection through the crust and the mechanical strength of the crust.  This is where there is enough energy to prevent the magma and crust to cool too quickly.
a trigger to set the whole pressure cooker off - most likely an earthquake, or a series of quakes that start a caldera collapse for example.
a recent study suggests that the assimilation of water bearing crustal rocks into the magma at Toba increased its water content, and therefore, explosivity.

Essentially, a VEI-9 eruption could be classified as a 'megavolcano', the consequences of such a volcanic eruption would be absolutely catastrophic.


How closely related is surface air temperature to pressure? Obviously with a given mass and volume of air, pressure is directly proportional to temperature. However, I would expect the total mass of air within a column of atmosphere to vary over time, due to atmospheric waves (and oceanic waves, over the ocean).

How highly correlated is surface air pressure with surface temperature, at a given site? How much does the variation of atmospheric mass affect that relationship?

You have opened a very large can of worms.  You will need a larger can to get them all together again.

The problem is time lag.

Let's do some thought experiments:

It's dawn in the desert.  Right now the bottom of the atmosphere is cool.

Sun heats the dirt, and the dirt heats the air.  Air expands some.  But the air above it is lazy about getting out of the way.  So the air pressure goes up some.  Air finally shoves that air above up, and then whether the pressure goes up or down depends on how fast it can get out of the way.  Small area -- parking lot, the air spills in all directions.  adjusts quickly.  Gobi desert air starts to push out sideways, Coriolis rears up, and you have a temporary high pressure.  At night the reverse happens.  Ground cools, air shrinks, but the air around it doesn't fill in right away.

Lets look at longer term features.  Consider the Alaska low.  The north pacific is warm, at least by ocean standards, and so the air above it is warm.  Warmer air is less dense, and since the low stays more or less put for months at a time, the entire air column is warmish.  Warm air is less dense than the cooler air around it. It has a lower effective surface pressure than cooler air around it. The cooler air from around it tries to rush in, but... Coriolis again. Friction restricts how much of that air can enter the low area. Low pressure warm air is pushed out by moving upward as a series of cloud and rainy weather.

We think of the atmosphere in our heads as this thick blanket covering the earth.  But most of the interesting stuff is in the bottom 3/4 of the atmosphere (by mass) which is about 36,000 feet. Call it 5 miles. It's a thin apple skin.

One of the messy bits is the scale problem:  There is very little change in energy moving a parcel horizontally.  But moving it vertically gets messy.  Pressure changes.  Temperature changes.  Water condenses/evaporates adding/removing sensible heat.

One of the eye openers for me was realizing that in a lot of physics, you can analyze and quickly conclude that certain forces have small effects and can be ignored.  In atmospheric dynamics I find myself unable to figure out what can be ignored, or left with a first level approximation.  Everything affects everything else.

Anyway to answer your question:  Warming temperatures will initially increase pressure, but later decrease pressure.  Cooling temperatures the opposite.

Looking at Edmonton, AB's forecast for the next 10 days, we are getting daily temp fluctuations of about 11 C, and daily pressure variations of about 4 hPa.

From the gas laws this is an 11 K compared to about 300 K so the pressure should change by about 11/300 of it's absolute pressure.  This would be about 37 hPa.  Why doesn't it?

Because it's not the whole air column that's changing temp.  Typically only about the bottom 3000 feet changes on a daily basis -- daytime mixing depth, with some mixing higher up.  3000 feet has about 1/10 of the atmosphere in it so the variation is only about a tenth.  Ok, that gives 3.7 hpa.  Closer to 4, but still off.  Remember you ignore factors at your peril in atmospheric.


Does Start / Stop technology in cars have an impact on air quality? I have repeatedly heard from various car enthusiasts that start stop technology has no benefit (or the tiniest smallest negligble benefit) to air quality so they turn it off entirely.  Does it have an effect and how much?

I live in a busy town with many traffic lights in the centre with many traffic lights in the centre, there is a taxi rank where taxis idle for minutes at a time, there are high streets where cars wait outside shops and there are bus stations where buses leave their engines running while loading up passengers.

Generally idling will cause pollution in specific isolated areas and start stop technology could irradicate that pollution.  Here I will concentrate not on the global impact of the pollutants but at the location where the pollution is released.  The differing scenarios are important to how much of an effect start-stop / idling will have on air quality.  The location affected by idling will of course determine what air quality affects.  Taxi ranks, junctions, high streets, spaces outside schools, hospitals and other areas where cars often stop for longer than a few seconds.  The longer you idle and the more cars there are, the more pollution you would create in that specific location.  The number and type of person in the location where the idling is taking place would make a difference to how the air quality would affect people.

I present a few scenarios (a link at the bottom for my calculations)

A long journey with minimal stopping
Here the savings on pollution would be negligible because the car would not be stopped idling for much time at all!  Although of course the locations where the car does stop would be subject to fewer pollutants.

Major junction at 11:30am on a weekday (figures taken from Preston Circus Brighton)
During a full cycle of all traffic lights going from red to green and back for all junctions, 69 cars passed during 112 seconds.  The cars used an estimated 0.451L of petrol.  During this time 32 cars waited for 30 seconds using 0.2L of petrol.  Idling in this scenario is responsible for 44% of the fuel used and therefore I assume idling is responsible for 44% of the pollution.  It is a place where pedestrians will wait at crossings, drivers will sit in their cars, cyclists will stop catching their breath and where pedestrians sometimes have alternative routes.
44% here is a huge and very significant number.

Single car waiting in a single spot
In a car you would use around 0.75L of petrol per hour idling and you would change that single location from being pollution free to a place equal to a single lane road with regular traffic (1 car every 12 seconds)

A 1.5km stretch of road with 4 major junctions with traffic lights
A single 1.5km stretch of road could have four major junctions in a busy city.  A car stops twice for a combined total of 2 minutes.  The car will use around 0.025L of petrol idling.  Driving along this stretch of road would use around 0.15L of petrol, assuming the amount of fuel is equal to the pollution then start stop could reduce pollution by 6%.  This is a fairly small amount compared to the total but it is still significant difference in the air quality along a large stretch of road.  Streets like these in city centres will have many more people than in other areas waiting at the lights, walking along pavements, people working in shops, people living in flats above the roads, cyclists and drivers will be in their cars taking in the pollution.  These areas are some of the most dangerous generally for people because of the number of people so 6% could make a significant difference.

A taxi rank
A taxi rank with 10 cars idling in a space of around 35m. That 35m spot could have the air quality equal to a reasonably busy dual carriage way (a car every 1.68 seconds).  Some taxi ranks are covered (such as those near train stations) which could make those spaces much much worse as the pollution would not be dispersed easily. There will be people waiting for taxis next to the taxi rank, people waiting nearby as taxi ranks are usually in busy locations and the taxi drivers themselves will be sitting directly in these toxic fumes so there will be many people exposed to this pollution.  With start-stop, this pollution would be completely eradicated.

A school
The cars could be spread out more so you could say it would be a half of the above, so a busy single lane A road maybe.  The affects of pollution are greater on children because their lungs are smaller, more sensitive and growing.  Children and babies in prams are also more affected because they are shorter and closer to the pollution.

https://docs.google.com/document/d/1rASB96LRIP1II4vkxGKncshfZpR3iNAy9ONmSHAkTGs/edit?usp=sharing


What is this (possible) fossil from the triassic/jurassic boundary? My son recently found this:

while walking at Waterloo Bay in Northern Ireland. It looks (to my untrained eye) like it could be a plant fossil. Is this correct? If so, is it possible to tell anything more about it?

It was found at the boundary of the Triassic and Jurassic layers, but had been broken free so might have come from elsewhere. The rock type matches the Jurassic layers. The included photograph covers a height of 15-20cm.

Its definitely a flowering plant which evolved in the early Mesozoic Era. Also, Pangaea was beginning to break up, but not fully broken up so climate would be than likely be Continental-Maritime allowing for dry weather and water cycle contributions from the surrounding body of water as it broke apart. Also, this land was positioned a little closer to the equator at that time and if found in Ireland, it would have been 'attached' to northwest Africa and the east coast of North America to the west making it possible from a climate and geographical situation. Have a look at this video of Continental Drift movements of parts of the world at 200 million yrs ago in the roughly similar time period you suggest: view at 3:47 for 200 mya and 4:03 to view the recognizable formation of the British Isles. Enjoy! https://www.youtube.com/watch?v=UwWWuttntio


Please help me identify these two rocks? Two rocks both green, one is transparent, the none transparent rock is extremely tough almost impossible to cause a scratch on it.

Thanks

The photos are pretty bad but a couple of things still stand out, the translucent sample shows apparent conchoidal fracture which coupled with the colour and level of transparency makes me think it's green Obsidian. Obsidian is a volcanic glass and can be mistaken for manmade glass, what is sold as obsidian in many stores is in fact not a natural substance at all. Also as I should have pointed out originally without some scale and clarity the sample presented may well be a broken piece of manmade glass.

The second photo is a little clearer, the apparent fine layering and particular shade of green looks just like a sample of fused volcanic ash I have that came from Mount Tongariro.


What caused the Younger Dryas cold event? During the termination of the latest ice age the warming climate leading from glacial to interglacial conditions was abruptly reverted by a distinct but short (about 1300 years in duration) cold event, referred to as the Younger Dryas. This event resulted in substantial moraine zones around the southern edges of the Fennoscandian ice sheet, indicating a halt in retreat. There are also evidence of strong permafrost conditions in the periglacial area. What caused this cold event?

The most accepted theory is that the Younger Dryas was caused by a large reduction or shutdown of the North Atlantic "Conveyor" because of a sudden influx of fresh water from Lake Agassiz and deglaciation in North America.
(Although evidence for such an event is thus far lacking.) The global climate would then have become locked into this new state until freezing removed the fresh water "lid" from the north Atlantic Ocean.

Another theory suggests that the jet stream shifted northward in response to the changing topographic forcing of the melting North American ice sheet, which then brought more rain to the North Atlantic which freshened the ocean surface enough to slow the thermohaline circulation.

http://geosciencesocietysio.wordpress.com/2014/05/04/paleoclimate-what-caused-the-younger-dryas-event/


Hydrology- flow accumulation I'm not specialist in hydrology, and I  would be very grateful if you answer my question:

What is flow accumulation in hydrology?
Why algorithms used to calculate it over a raster DEM don't take rainfall rate into consideration?
For example when I use richdem python library to plot flow accumulation what is the range and unit of values shown ?

The flow accumulation algorithm essentially determines the upstream contributing area of every grid cell; in other words, what area or how many other cells will drain into a given cell. The flow accumulation algorithm is independent of rainfall as it simply determines which areas drain where, which will later be used to determine how much water actually flows based on the rainfall event and the area on which the rain actually occurs. However, the first step is just to figure out the flow directions.

The flow accumulation is typically done as part of a series of algorithms with a given DEM to determine where the river network exists and what the catchment boundaries are. This type of analysis is required in order to delineate watersheds (i.e. determine where the watershed boundaries are and how large they are) and create the building blocks for a hydrologic model, which is used to simulate the rainfall-runoff response and flows at given points, among other processes.

The flow accumulation algorithm typically used is the D8 algorithm, although if you look into the literature there are lots of versions and variations on determining flow accumulation. I am not familiar with the richdem python algorithm, but the units will be some measure of either upstream contributing area or number of upstream units in every grid cell. You will notice that the areas downstream and near outlets of watersheds have higher values, indicating that those areas receive larger contributing areas from the rest of the watershed. The next step in the analysis, likely a flow network tool, will use the grid cells with the largest flow accumulation values to determine the existence of a river network based on high accumulation values (with some value as a threshold).

The ESRI page has a good discussion on how flow accumulation works as well.

Examples

Watershed delineation can be done automatically from a DEM layer, and there are a huge number of tools to do so. Here are some tutorials and guides with GIS software, other tools exist in R or python (as you pointed out).

ArcGIS Watershed Delineation Tutorial with Arc 10.2

QGIS Watershed Delineation Example

Note that prior to the use of DEM tools, contour maps would be used to delineate watersheds by hand. This is done essentially by drawing outlines which cross contours perpendicularly through high areas, and encompass the watershed. A couple examples of that here for you as well. Note that these will not have flow accumulation since that cannot be done easily by hand, that is only a step using the computational tools.

US Department of Agriculture Example

Miscellaneous contour example and slides


What is the time-lagged correlation between historical $\ce{CO2}$ records from ice cores and global temperature records? Is there a time-lagged correlation with CO2 levels preceding temperature? Does the time lag change from time to time?

From wikipedia:

  Studies of the Vostok ice core show that at the "beginning of the deglaciations, the CO$_2$ increase either was in phase or lagged by less than ~1000 years with respect to the Antarctic temperature, whereas it clearly lagged behind the temperature at the onset of the glaciations".$^{[1]}$ Recent warming is followed by carbon dioxide levels with only a 5 months delay.$^{[2]}$ The time lag has been used to argue that the current rise in CO$_2$ is a result of warming and not a cause. While it is generally agreed that variations before the industrial age are mostly timed by astronomical forcing,$^{[3]}$ a main part of current warming is found to be timed by anthropogenic releases of CO$_2$, having a much closer time relation not observed in the past (thus returning the argument to the importance of human CO$_2$ emissions). Analysis of carbon isotopes in atmospheric CO$_2$ shows that the recent observed CO$_2$ increase cannot have come from the oceans, volcanoes, or the biosphere, and thus is not a response to rising temperatures as would be required if the same processes creating past lags were active now.$^{[4]}$

Historical carbon dioxide record from the Vostok ice core - Carbon Dioxide Information Analysis Center, 2003.
Spencer R. Weart, 2006, The Discovery of Global Warming
Kuo et. al., 1990, Coherence established between atmospheric carbon dioxide and global temperature
More Notes on Global Warming - Physics Today, 2005


Are clouds significantly easier to simulate in weather models than climate models? Cloud forcing is still one of the major uncertainties of radiative forcing in climate modeling because there are so many uncertainties in it (and parametrizations). But also because the timescale of cloud development are much shorter than the timescale that climate models are run at.

So I'm curious: are clouds much easier to simulate in the short timespans of weather models? Or are they still a beast to simulate in them?

The answer to this question depends on what process one is interested in simulating well. As you know, short/mid-range weather prediction models and climate models have very different applications and goals.

Because the short range weather prediction model is typically of much higher resolution than climate models (~1-10 km versus ~50-200 km), it is almost always more skilled at simulating clouds forming at a specific location and time. Cloud and rain prediction skill tends to be greater in synoptic scale fronts and near topographic features, and smaller for sporadic, small-scale, tropical thunderstorms. In very high-resolution NWP models (2-3 km or smaller), convection and clouds may be simulated reasonably well without using any cloud parameterization scheme. Nevertheless, clouds and rainfall are still hard to simulate or forecast very accurately.

On the other hand, due to very low grid resolution, climate models can really aim only for correctly simulating the occurrence frequency and the amount of clouds and rain in a larger geographical region over a longer period of time. In climate, clouds play a significant role in radiative feedbacks. Climate models still rely on cloud parameterization schemes.


Why does the Northern polar vortex usually have two centers? From http://glossary.ametsoc.org/wiki/Polar_vortex

polar vortex
A planetary-scale mid- to high-latitude circumpolar cyclonic circulation, extending from the middle troposphere to the stratosphere. The Northern Hemisphere vortex often features two centers—one near Baffin Island and the other over northeast Siberia—with analogous circumpolar asymmetry atypical in the Southern Hemisphere. (emphasis mine)

Why does the Northern Hemisphere polar vortex often have two centers, as opposed to one for the Southern? I gather that this may have something to do with the Arctic vortex being elongated in shape, but this leads to the question of why it is elongated? Does it have something to do with the terrain features below?

Northern Hemisphere

The spatial structure of the polar vortex is determined by the stationnary waves. Stationary waves in the northern hemisphere are primarily modulated by stationary (surprise!) forcings of the northern hemisphere :

Topography : Rockies and Himalayan mountains
Land-sea ocean heating contrast

This spatial pattern is mostly locked but they are slightly modulated by the seasonaly changing meridional temperature gradient and from internal chaotic processes (i.e. turbulence).

This article is a must-read and not too technical for the northern hemisphere circulation:

http://onlinelibrary.wiley.com/doi/10.1029/134GM01/summary

vs Southern Hemisphere

When you compare such forcings between the northern and southern hemisphere, there is a big difference: much less land-sea contrast and less topographic forcing in the southern ocean. Hence, a "wavenumber one" configuration, as compared to a "wavenumber two" for the northern hemisphere.


What is the impact of divergent tectonic plates on old mountain ranges? I found this question, which is similar to what I'm wondering, but my question is slightly different:

What happens if a new divergent boundary forms in a way that bisects a mountain range, especially one formed by converging plates -- and is that even possible?

Purely for the sake of example, if a divergent rift somehow formed on the North American plate, dividing the Appalachians [ETA: apparently I circled a valley, please pretend I'm not a geography-illiterate dork and that it's actually some old mountains.]:

What would happen to the circled area? Anything? Would the mountain range be recognizable after an ocean formed between them? Considering the timescale involved, perhaps an older range would be unrecognizably eroded? I've tried to find examples in the real world, but my Google-fu fails me.

Somewhere I picked up the idea that the Appalachian and Welsh coal seams were once connected or formed together (I think it may have been from an offhand comment in a movie about Welsh miners, so a] maybe I understood wrong and b] who knows how accurate it was), so I initially wondered if that might be an example of what I'm curious about. Unfortunately, some light research seems to indicate that's not the case (if I'm understanding this and this correctly, the connection ends at "both formed, at least partially, during the Carboniferous.)

I'm most interested in what the effects (if any) would be on older mountain ranges such as the Urals or Appalachians, but if anyone knows what kind of effects it might have on younger, taller ranges, I'd love to hear about it.

If anyone has sources I could look into for a deeper understanding, I'd love to have those as well! My lack of knowledge is distressing me to no end.

The example of the East African Rift was given in a different answer.

Splitting of mountain ranges in two becomes even more apparent as you go up north from there.

The Red Sea between Egypt and Saudi Arabia is a young new spreading ocean, that cuts through Precambrian mountains.

Further north from there, the Dead Sea is a combined transform–rift zone where you have the same thing. Precambrian mountain ranges overlain by Cretaceous sediments (folded into mountain ranges) are being torn apart to form the Dead Sea depression.


Why is ozone layer so important when oxygen atoms absorb UV Rays? Oxygen molecules absorb UV Rays and are converted to elemental oxygen atoms. These elemental oxygen atoms combine with molecular oxygen to go give ozone .
When there is so much oxygen present in atmosphere how will UV Rays reach us? Are we concerned about oxygen being depleted?

Why is ozone layer so important when oxygen atoms absorb UV Rays?

The cross section of ozone to UV radiation is many, many orders of magnitude higher than is the cross section of $\text O_2$ to UV radiation, so very much higher that despite the paucity of ozone molecules compared to diatomic oxygen molecules even in the stratosphere, it is the ozone molecules that tend to absorb incoming UV radiation.

When there is so much oxygen present in atmosphere how will UV Rays reach us?

Oxygen has a low cross section to UV radiation. It absorbs some, but not very much.

Are we concerned about oxygen being depleted?

Not at all. Suppose the ozone content did become rather high compared to nominal. This would increase the rate at which ozone combines with monatomic oxygen to form to diatomic oxygen molecules. Ozone is a transient component of the atmosphere. It is constantly being created but is also constantly being destroyed.


sulfur hexafluroide as a greenhouse gas and its atmospheric journey Maybe a simple question, but if sulfur hexafluoride is 6 times heavier than air then how does it get into the high atmosphere. All be it in low quantities now, but there is a large stock of the stuff in potentially vulnerable and prevalent infrastructure such as substations of the electricity grid. If there was a much larger leak of the chemical than is now observed would we expect it to reach the upper atmosphere to become a dangerous greenhouse gas at that position in the atmosphere... as i understand potent ghg's induce greater warming when high in the atmosphere. Anyone know more about this? its mode of transport there, what activities are getting it up there? Ive done some research on existing and past growing concentrations but wonder if its Global warming potential is dangerous unless it can actually accumulate significantly high in the atmosphere?

Carbon dioxide is heavier than air but is found in nearly equal proportions throughout the well-mixed portion of the atmosphere. Xenon is much heavier than air, almost as heavy as sulfur hexaflouride, but it too is found in nearly equal proportions throughout the well-mixed portion of the atmosphere.
Turbulence is what makes the well-mixed portion of the atmosphere be well-mixed. It is only in the uppermost layers of the atmosphere, where the air is very thin, that turbulence fails to keep things well-mixed. The turbopause, which marks the border between the well-mixed lower portions of the atmosphere and heterogenous upper portions of the atmosphere, is about 100 km above the surface. The stratosphere is only 10 to 50 km above the surface, so it is well within the well-mixed portion of the atmosphere.


How can there be a hot summer with rain and no thunderstorms and lightning? This summer in the south of France we have had two hot months with 29 days over 30'C, while the average maximum is 26'C in July.

Normally there are violent storms with lightening up to 20 times a minute, and this year in two months we have had 20-30mm of precipitation rather than the average of 120mm, and there hasn't been any thunder and lightning since the 15th of june.

I am confused why we have only had meek drizzly rainfall, because of weak cold fronts, insufficient moisture from the east, did the high heat cause the rain to not condensate in the high atmosphere?

This is an El Nino summer, and a very strong one and a very weird one at that. Weather patterns are messed up world-wide. Apparently a stable high pressure cell has set up that oscillates back and forth between just east of Barcelona to eastern Europe.

France suffers when that high pressure cell is just east of Barcelona. That high pressure cell off Barcelona means France is in that thick of it. Moderately high temperatures and low humidity rule the day. The chance of rain is drastically reduced, and the chance of abnormal high temperatures is drastically increased.

France suffers even more when that high pressure cell migrates to the northeast. Now the clockwise rotation of the high pressure cell carries extremely hot and extremely dry air from the Sahara towards France. If on the very odd chance that you do see clouds, and on the odder chance that you do see rain falling from a cloud, the odds are that you'll see the rain disappearing halfway to the ground.


How deep could the surface of the Earth's crust get? In theory, how deep can a natural formation on the surface of the Earth's crust be? What are the limits to this depth?

Challenger Deep (10.99km) in the Mariana's Trench is the deepest part of the ocean floor. This is probably close to the deepest theoretically possible ocean floor with the  current thermal regime.

With the current thermal regime, the deepest 'steady state' ocean floor depth is about 5.5-6km ( cooling curves at Muller et al ) - limit is reached as the ocean crust cools and subsides. The crust (lithosphere) is effectively floating on the mantle (asthenosphere), and this steady state situation is known as 'isostatic equilibrium'.

You can get deeper by moving from a static to a dynamic situation. A subduction zone provides this - the subducting plate is moving and being pushed down, resulting in a deep ocean trench. Eg. The Mariana's, or the trench offshore Chile. A fast subduction zone should go deeper. A deep hole like this will also tend to fill with sediment. The fastest subduction zones move at about 16cm (and these are only the short arcs). The physical characteristics of the ocean crust will also vary a little (thickness, temperature), but beyond these parameters it is difficult to make the hole deeper, as it were.


At what point is the atmospheric pressure considered to be high or low? I am working with a program that I want to inform the atmospheric pressure level at atm and if the pressure is high, low or average in a certain location, but I have not found anywhere on the internet that can give me an idea of how to calculate this. Could anyone tell me at what level of atmospheric pressure it can be considered low or high? is there any specific point? Do I need some more information to calculate this?

Usually when you hear someone say "high" or "low" pressure, it is an abbreviated way of saying "local maxima" or "local minima." And usually that pressure is the Mean Sea Level Pressure. By that definition, it is a singular point. But if you want to cover an area, you can probably reference a gridded dataset and plot the isobars. Then you can categorize the isobars as cyclonic (low pressure in Northern Hemisphere) or anticyclonic (high pressure in Northern Hemisphere). Then you can say if the location is enclosed in either, then it is in the respective area. You can make it however complex you want.
But if you want to create your own "pressure climatology" then you can probably do what you want to do.


How bad is a "bad" oil spill? I live in British Columbia, and a hot topic right now is the proposed Enbridge pipeline. One aspect in particular gets a lot of attention, the risk of a "bad oil spill". Is there a clear guideline as to what exactly constitutes a bad oil spill? How much oil must be spilled? Is it dependent on what type of oil is spilled and in what area, populated by what species? Looking for some general guidelines.

Is there a clear guideline as to what exactly constitutes a bad oil spill?

No, "bad" has no legal definition in any jurisdiction in North America. As a practical matter you can only establish regulations and enforce legal penalties, regulatory, civil or criminal by some sort of numerical, measurement based criteria.

  How much oil must be spilled?

All material economic activity has some sort of negative tradeoff, all jurisdictions have some level of permissible harm. Each jurisdiction a pipeline passes through will have some level of oil leakage or other types of environmental harm that are permitted without triggering as legal consequence for the operator. However, this does not define "bad" but merely the trigger threshold.

An international pipeline like the Enbridge pipeline that crosses countries, provinces, states etc will be subject to a different set of rules for every jurisdiction and at times combinations of jurisdictions. You'd have to check each individual jurisdiction to find the threshold for each one.

  Is it dependent on what type of oil is spilled...

Usually, yes. Since the primary harm from oil is mechanical, the viscosity of oil is the prime predictor of the harm it will cause if spilled. Crude oil varies in viscosity from a thin syrup to thick paste. The former can spread fairly far in warm weather while the later usually just piles up at the leak. The former causes more harm per unit of escaped volume than the later.

Most of the oil moved in the Enbridge is dilbit a diluted form of bitumen/asphalt from the tar sands. Bitumen/asphalt is arguably a solid so it has to be diluted with something else to make it a pumpable liquid. Depending on the viscosity chosen, the spread and mechanical risk will vary as well.

The diluent itself is going to be something volatile which could in principle constitute a greater toxicity danger than simple crude oil. Naphtha has been used in the past which is the most volatile fraction of any crude oil. Depending on the actual ratio, spilled dilbit will present a greater or lessor danger than a comparable (usually light) crude.

  and in what area,

Quite definitely.  As noted above, the oil does not spread to any significant degree without water transport. A pipeline crossing a body of water or running near one will require more rigorous construction and closer monitoring than one that does not. Oil pipelines crossing desert or arid regions cause much less harm be unit of leaked volume than do pipelines in swamps or under body of water.

  populated by what species?

Usually, but again, this varies considerably depending on jurisdiction.


How to determine constant $C$ in $p(x) = Cx^{-D}$? Given a distribution obeying the power-law (fractal) relation, such as the cumulative distribution function $L_{cf}(> X) = CR^{-D}$, if $X$ is given, how does one find the constant $C$ from a given data set?

For example, given this table:

[Source: C. Li et al. / Geomorphology 130 (2011)]

how does one determine how the values for $L_{cf}$ were obtained? It appears that they used the method of least squares fitting to obtain the values for $D$, but I don't seem to understand where the values for $C$ are coming from. Any help would be appreciated.

There are two solutions using the least square method for calculating $C$ and $D$. Both methods yield different results for your constants. There is no correct method.

Method of least Squares

We define the least square error as follows:
$$\text{lse} = \sum_{i}{\left(y_i - f(x_i)\right)^2}$$
The $y_i$ and $x_i$ are our data through that we want to fit a function $f(x)$. The aim is to reduce our error $\text{lse}$.

The solution (minimal $\text{lse}$) for a linear function $f(x) = a \cdot x + b$ is described here. The basic idea for calculating the minimum of $\text{lse}$ is to set $\partial \text{lse}/\partial a$ and $\partial \text{lse}/\partial b$ equal to $0$ and solve the resulting equation system to $a$ and $b$.

Having said that we come to two solutions for calculating $C$ and $D$ in $f(x) = C\cdot x^{-D}$

Solution 1: Logarithmize the Function

We rewrite
$$y_i = C \cdot x_i^{-D}$$
to
$$\ln{y_i} = \ln{\left(C \cdot x_i^{-D}\right)} = \ln{C} - D\cdot \ln{x_i} $$

Now we have a function of the form $\tilde{y_i} = a\cdot \tilde{x_i} + b$ with $\tilde{y_i} = \ln{y_i}$, $\tilde{x_i} = \ln{x_i}$, $a=-D$ and $b=\ln{C}$. Thus, we logarithmize our measured $x_i$ and $y_i$ values and put them into the formulas of the linear least square error method. From the resulting $a$ and $b$ we than calculate $D$ and $C$.

Solution 2: Insert the Function as it is

We set $f(x) = C\cdot x^{-D}$, insert it into our $\text{lse}$ formula:
$$ \text{lse} = \sum_i{\left(y_i - C\cdot x^{-D}\right)^2}$$
and minimize the resulting formula with respect to $C$ and $D$ for the given set of $x_i$ and $y_i$. This is a tricky and not as straight-forward as it is in the linear case. You could make $\partial \text{lse}/\partial C$ and $\partial \text{lse}/\partial D$ and look how far you come.

I personally, prefer the answer of Gordon Stanger :-) .


How much does the electric current within the Earth' core depend on the axis of the Earth's orbit? I always thought that the movement of the iron core was caused by the axis of orbit of the Earth. Probably that isn't quite as true as I read, because in the core the iron material undergoes types of swirls. I read that there exists about 6 or 7 swirls in the outer core, with the one under Asia the fastest, creating a bigger magnetic field, and the one under America the least active, giving a weaker magnetic field.

So if those swirls underneath the continents are stationary, the current swirls aren't caused by the Earth's orbit axis. Instead the swirls arise due to the cycle of material rising, solidifying, and sinking back to the core. But I'm not sure I understood this well.

But nevertheless, isn't the current that causes the magnetic field affected by the Earth's axis (or perhaps the orbit around the sun)?

There's still a lot that isn't understood about the Earth's magnetic field, so there's some uncertainty to any answer to your question.   That said, I touch on some of it.

  isn't the current that causes the magnetic field affected by the
  Earth's axis

I'd say probably not.  We can see this by looking at other objects with magnetic fields relative to their axis.  There are some theories that planets need to rotate to have magnetic fields, but Mercury rotates very slowly and it has a small magnetic field.  Mars rotates with a similar period to Earth and it lost it's magnetic field about 4 billion years ago.

and Neutron Stars.

  Often, the magnetic field is not aligned with the spin axis

The Magnetic Axis and the Axis of Rotation seem to have very little to do with one another.  The Rotation Axis' relation to the plane of the solar system, I suspect that has even less influence, but I have no idea how to go about explaining the why behind that, it just feels improbable to me because the effect seems more internally generated and the inside of the Earth cares which way it spins and stretches, but not how it lines up with the plane of the solar system - (I would guess).

In addition, the Earth's Magnetic North Pole moves around.  Earth's Axis changes very slowly.  It's difficult to see a relation between the two beyond "in the same general area".

  (or perhaps the orbit around the sun)?

It's always good to explore possibilities.  Pretty interesting, short article on Mars' loss of it's Magnetic field here that suggests it's the inner workings of the planets that drive magnetic fields.

When there's enough temperature variation and a liquid medium, spirals (or swirles) can form because circulation is more efficient than convection at heat transfer.  Like the atmosphere, you also have the hotter material wanting to expand and rise and the cooler more condensed material wanting to fall, but you also have increasing pressure as you go down, and, perhaps, not uniform molecular density, so it's a pretty tricky subject requiring lots of math behind when spirals form and when they don't.  The solidifying of the other core into the inner core and heat released from that phase change may play a role too.  (I read that, will post a source if I can find one).

Earth's relatively rapid rotation (and corresponding Coriolis effect) might keep the magnetic field pointing roughly North-South (I would guess) but as noted in the map above, there's a fair bit of wobbling and in addition to that, every few hundred thousand years the field flips.

The Moon may cause the movement of the magnetic poles too.

  (or perhaps the orbit around the sun)?

(yes, I just quoted you twice)

That article just above suggests the stretching and squashing of the Earth, both due to the Moon and the Sun would have an effect, so in a sense, the Orbit around the Sun might affect the magnetic field, but more the tidal effects from the Sun than the actual orbit itself.

Because this field remains unresolved, we should never say never until it's better understood.


Is there a formula that gives the temperature of an object or person exposed to the sun? It is well known that temperature sensors are often shaded, partially to mitigate the variability due to varying cloud cover. However, most people experience temperature within the sunlight. Other measurements of temperature that describe how temperature is felt are the heat index and wind chill, but both neglect the effect of the sun. For example, a very low wind chill can partially be overcome by a clear, sunny day.

Is there such a formula that perhaps gives an upper echelon of experiential temperature? I envision such a formula would involve the solar angle, albedo and perhaps the radiative balance.

It is not an easy problem even for a simple object. The temperature will vary as the conditions change, but the usual approach to such problems is to find the equilibrium temperature for a set of conditions. This is, to find the final temperature that the object will reach if exposed to a given solar irradiation, with air at a given temperature, for given pressure, humidity, wind, etc.

Such equilibrium state will allow you to find the temperature by assuming energy balance. That can be stated  as requiring that the incoming energy into the body equals the outgoing energy, or

$Ẹ_{in} = E_{out}$

To simplify the explanation let's assume the object was in equilibrium with air temperature during the night and we want to calculate its temperature onces the sun is shining on it. In this case the incoming energy will be function of the absorbed solar energy, therefore it will be function of the radiation intensity ($R_{sun}$) that depends on solar elevation, cloud cover, etc. (and can be obtain as a direct output of climate models), the albedo of the object ($\alpha$) and the area exposed to sunlight (i.e. coross-section) ($A$), that will be given by the shape of the object, solar elevation and azimuth. So, that is equivalent to:

$E_{in}=R_{sun} (1-\alpha) A$

Now, the energy leaving the object will have two components.

Radiation: The object will cool down emitting electromagnetic radiation (mostly infrared) according to the Stefan-Boltzmann law.
Conduction: As the object get hotter than the surrounding air, it will loose heat by thermal conduction into it.

So

$E_{out}=\kappa (T - T_{air}) + \varepsilon \sigma T^4 S$

Where $\kappa$ is the thermal conductivity of air, $T$ is the temperature of the object and $S$ its surface area. $\varepsilon$ is the emissivity (that is 1 for a black-body), and $\sigma$ the Stefan-Boltzmann constant.

The three equations above are sufficient to solve for the temperature of the object, but as you can see there are many parameters that depends on the object shape, and material, so it is impossible to generalize.

Also, in the absence of wind, the temperature of the air in contact with the object won't be the same as the surrounding air, further complicating the problem.

Furthermore, in addition to $A$, $\varepsilon$ and $\alpha$ can as well change with solar elevation and azimuth (if the object is made out different materials).

And to further complicate the problem, the thermal conductivity of the air $\kappa$ is a function of temperature, pressure and humidity. And it is not an easy relationship, it is usually tabulated or calculated using empirical formulas.

At engineeringtoolbox.com you can find tables and graphs of $\kappa$ for dry air, here is one example:

But the humidity have also an impact much more difficult to quantify, and whose importance grow with temperature. There is an article at electronics-cooling.com that explain the effect, summarized in the following graph:

So, that is hard enough for an object, let alone for a person. In such case there would a lot more parameters that come to play. Like the amount of insulation provided by clothing, surface and moisture content of the skin exposed to the wind, body heat production, etc.

Apparent temperature

That been said, there are some attempts to estimate the perceived temperature for people including humidity, wind and solar radiation. The best example is perhaps the Wet-bulb globe temperature ($\mathbf{WBGT}$), that consist on the weighted mean of the readings of three different types of thermometers: A normal one, a wet-bulb one (affected by wind and humidity) and a very uncommon black-globe thermometer (affected by solar radiation).

The formula is:

$\mathbf{WBGT} = 0.7 \, T_{wet-bulb} + 0.2 \, T_{black-globe} + 0.1 \, T_{air}$

However, this value is not often used because is very location specific (depend on clouds for example). Nevertheless, perhaps a good approach you can take is to use actual solar irradiation from weather models to compute the temperature that a wet-bulb and a black-globe thermometer would produce, something that I think would be easy to achieve, and then compute the $\mathbf{WBGT}$ with the above formula.

Be aware that the $\mathbf{WBGT}$ value could be useful for people to know how cold/hot it will feel, but won't tell you anything about the actual temperature of different objects exposed to those conditions.


About moving ice bergs northwards to slow down all the melting a tiny bit. ( Clearing away navigation hazards is a side effect of this.) I read somewhere someone someone had the idea to try to move a 'small' iceberg with giant tugboats used to move oil-rigs. I thought if an Iceberg could be moved, why not move it $NORTHWARD$ maybe above the latitude of where it 'broke' off. Maybe it could be anchored there somehow. Is this feasible?

Some background. The idea of towing ice bergs to provide a source for fresh water in dry climate zones was first proposed in the 1970s by Weeks and Campbell (1973) and Hult and Ostrander (1973). This sparked interest that resulted in several studies published in conferences (Husseiny, 1980; IGS, 1980). The focus of the work was manly on the wastage of ice during transport and of course the technical aspects of towing ice. The main issue, however, concerns the integrity of ice bergs during transport. The mechanics of ice bergs is still poorly understood and it is known that bergs gradually break up. How this is affected by ocean swells and other forces acting upon a berg under tow is still investigated (see a wealth of publications in particularly Journal of Glacology and Annals of Glaciology). The idea has, however, not been forgotten and more possible technical solutions are proposed (e.g. Fast Company. So while the financial aspect of the process may be calculable, the strength of ice bergs, and the forces acting upon them in the open sea and under tow requires more research before towing could become a reality.

On top of this are legal issues. Who owns the ice? and also how can towing ice berg across busy shipping lines be safe, particularly in the event of a break-up in mid-ocean.

To respond to your specific question on towing northward and anchoring: The towing in any direction is subject to the same issues as described above. Anchoring, the ice bergs will melt and degrade over time so that moorings will continually have to be renewed. Most ice bergs in the north will go through at least one cycle of being caught in seasonal sea ice but eventually will be set free to follow ocean currents in whatever direction they move locally. Since the ocean water will carry some heat, it will not matter where the ice berg is located, it will slowly melt. On top of that is the issue of disintegration since melting will change the shape of the berg and hence its stability and centre of gravity causing stresses within the block to alter.

If one takes a longer-term perspective and ignores the practicalities (incl. costs), moving ice to a place where it melts slower would momentarily decrease the contribution but eventually one would reach a new equilibrium where the same rate of melt water will be contributed and the temporary benefit will be lost. So apart from being highly impractical from all aspects, the longer-term benefits will be nil.

References

Hult, J.L. and Ostrander, N.C., 1973. Antarctic icebergs as a global fresh water resource. Rand Corporation, Santa Monica. Report No. R-1255-NSF. 83 pp.

Husseiny, A.A. (ed.) 1978. Iceberg Utilization. Proceedings of the First International Conference, Ames, Iowa, 1977. Pergamon Press, New York. 759 pp.

IGS (International Glaciological Society), 1980. Proceedings of the Conference on the Use of Icebergs. Annals of Glaciology, 1 136 pp.

Weeks, W.F. and Campbell, W.J., 1973. Icebergs as a fresh-water source: an appraisal. Journal of Glaciology, 12, 65, 207-233.


What control the atmospheric lifetime of different metals in aerosols? Background

I'm analysing the metallic elements in $PM_{2.5}$ to identify their possible anthropogenic sources for the study area.

A total of 19 metallic elements were investigated including dust-derived elements such as $Al, Ca, Mg$ and pollution-derived elements such as $Pb, Cu, Cd, Zn$

To better investigate the characteristics of different elements, their temporal variation (daily samples, collecting once for 6 days at an industrial city in China) during the whole year was analyzed.

I found out the burning of fireworks for celebrating China Spring Festival presented significant contribution to related elements, such as:

$Al, Mg$: they are utilized for the fuels of gunpowder.
$K$: the chemical compounds of $K$$ (KClO_4, KClO_3, KNO_3$) are usually utilized for the oxidant of gunpowder.
$Cu, Sr, Ba$ : used for generating lighting in different color.

Since the emission of firework burning were centered on the festival night, the influence should be short. We collect the aerosol samples and analyzed their species for the festival, one day after festival and two days after festival.

Observation results

Most of related elements presented the significant levels on the festivity and decreased sharply in the next day (~ 100 times).
However, I found three heavy metals with adverse health effects ($Pb, Cd, As$) had increases in concentration levels after the festival. Their concentration levels recovered to their normal level after 3 days.

My thought

Most of the related elements recovered to their normal levels in one day, the accumulation of $Pb, Cd, As$ should not be blamed on meteorological conditions;
There might not be other important sources leading to the continuous increases of $Pb, Cd, As$ in 3 days,

  Therefore, I though the accumulation of high concentration levels in 3 days should be attributed to firework burning,

This finding would be valuable since a short-time emissions event resulted in a relative long-time exposure to high concentrations if my inference is correct.

My question

Does the atmospheric lifetime differs for specific elements?  I assumed that the elements $Pb, Cd, As$ presented a long atmospheric lifetime with less deposition?
I still felt confused by the phenomenon. Any advice or comments on my question would be hugely appreciated!

You could say that metals and aerosols reside in the atmosphere but I'm struggling to call that "atmospheric lifetime", which I've only heard in reference to gases.  The residence time of particulate matter is mostly a function of meteorology (e.g. PBL height, wind speed) and deposition (e.g. raining, settling velocity).  You've observed some metals that had a longer residence time.  I can think of two reasons for that:

Unique reactivity with other atmospheric components will change the mass and deposition velocity of particles.  Metals that do not react well in the atmosphere may not grow as quickly and therefore settle more slowly.
Specific metals may be used more prevalently in fireworks that obtain high altitude, such that the metal emissions are injected further up into the atmosphere and subjected to more atmospheric mixing and therefore longer settling times.

You might find this article by Licudine et al., (2012) of interest, which discusses monitoring of metals on New Years in Hawaii.


If a person uses public transport, how much carbon is added to the footprint? For example if I use a public transport which is burning fuel with or without my presence, how one could calculate carbon footprint?

Hope I am in the  right place for asking this question.

I'm no expert on such subjects, but did Google and immediately this Guardian article offering a dataset apparently attributed to Camden Council/travelfootprint.org/Clear Zone Partnership.  There are a lot of different values, but (if I understand the columns labels correctly), a rough breakdown of the footprints would be ranges of:

Bus: 20-90 g CO$_2$/km
Train, Diesel/Diesel-Electric: 30-150 g CO$_2$/km
Train, Electric [Long-Distance or Subway]: 10-70 g CO$_2$/km
Flight: 190-460 g CO$_2$/km

Walking: 5-25 g CO$_2$/km
Biking: 7-18 g CO$_2$/km

Basic car, Diesel: 40-180 g CO$_2$/km
Basic car, Gasoline: 40-200 g CO$_2$/km
Basic car, Liquefied Petroleum: 30-180 g CO$_2$/km
Basic car, Natural Gas: 30-150 g CO$_2$/km
Basic car, Gasoline Hybrid: 30-150 g CO$_2$/km
Basic car, Electric: 7-110 g CO$_2$/km
Motorcycle: 20-190 g CO$_2$/km
Scooter, Electric: 4-30 g CO$_2$/km

[See the report for other automobiles, including family cars, SUV, and minis]

(The best end of the range is the more efficient models run at peak capacity in best conditions [rural roads/medium distance short-haul flights]
The worst end of the range is less-efficient models at quite low capacity in less-efficient conditions [urban roads/very short or long-haul flights]
[Rail appears fairly similar in all usage circumstances, thus only depending on model/network setup, at least in this UK data])

This data attempts to take into account secondary sources (such as power plants for electric vehicles or needs of the agriculture which is used for the energy to walk/bike).  As you can see there's a wide range depending on how most transport is used.  You're best suited diving further into the table to find the most applicable use case for you.

My list only shows CO$_2$... the database also includes NO$_2$ and some others pollutants (if you can break down the abbreviations!) which can be very important too.

And this is UK-specific.  So the equipment models used, network efficiency, and even climatological conditions will vary for other locations.

The date on the article also suggests its almost a decade old.  So we have likely seen some additional improvements in some formats (though it seems unlikely that they are giant leaps in most cases).

Hopefully someone will come along with more recent and wide-ranging data, but this seems like a good start at some rough estimates.


Are there any studies comparing different climate models on how well they've forecasted the climate in the past? E.g. IGCM, HadCM3, HadGEM1, GFDL CM, CGCM, CCSM, CFS, and ECHAM.

Yes. The biggest and broadest are the Palaeoclimate Modelling Intercomparison Projects (PMIP), which are the past-climate equivalent of the Climate Model Intercomparison Projects (CMIP).

The latest is PMIP3. It includes many of the same models that were used in CMIP5, as well as other models that are more focussed on representing past climates. The "overview" link on the PMIP3 page gives an indication of what the project covers, including experiments into the impacts of climate forcings, as well as benchmarking and comparison of models (e.g. quantitative and qualitative assessments of model performance over past climates).


What is diffuse plate rifting? For example in the Philippine Sea Plate the West Marianas Ridge has formed due to diffuse rifting in the south of the Marianas trough.  What does it mean?

If memory serves rifting is defined as either discrete or diffuse. Discrete rifting means that the crust is coming apart in one narrow area, usually in the form of a single defined split in the crust such as at divergent plate boundaries. Diffuse rifting is often seen in backarc spreading and involves many small localised extensional breaks in the crust, each break is small but with multiple breaks spread over a large area the total extension can be quite large. For example discrete rifting can be looked at as a 2 metre break along a single axis while a zone of diffuse rifting would involve several 1 metre breaks each with its own axis, all of which are parallel to each other and perpendicular to the direction of rifting.


Get atmospheric pressure values through JavaScript I'm working on a programming project in which I want to show isobars on a map with OpenStreetMap and the HTML tag canvas. The main problem that I'm facing is the dificulty of retrieving consistent data to draw the isobars and, therefor, calculate wind speed and direction.

I gave up trying to find real time data, and also I'm starting to doing so about getting open sea data (atmospheric pressure and temperature data in open sea, the first idea I had). So, right now, I'm searching for a platform where I can retrieve this kind of data in Europe (Spain in particular would be very nice) so I can start working on drawing isobars and calculating wind variables. I looking for measurements with some density (for example, 200 or 300 points of measurement across Spain within 4 times in a day) to draw the isobars.

The best (and kind of only) way to do so would be in JSON, because it would be quite easy to manipulate and work with the data, but also plain text would work.

Thanks to anyone who answers me.

There are some problems with your request, and maybe some misunderstandings.

Misunderstanding: You actually need more than pressure to get wind vectors. Wind speed is nonlinear, and is dependent on more than just wind. Even if you had observations of pressure, that will only tell you how the wind is changing due to the pressure gradient force, and not due to things like transport, diffusion, or Coriolis force, especially at the resolution you are requesting. Fortunately, wind observations are much easier to get than pressure observations, so that lies in your favor. You could use satellite data to get wind data, or near the surface.

Problem: Observations aren't really on a structured grid (unless you are working with satellite data, which has quality problems), nor are they available at the resolution you want. You may be able to use model data or reanalysis data, but even the resolutions you request may not be sufficient.

You can interpolate down to whatever resolution you want.

If you want near realtime model data for Europe, try the GFS model from the WPC. You can try to get data from the ECMWF (perhaps they have data sources I am unaware of), but their data is proprietary. You may also want to use a grib reader to access the data. If you are familiar with Python, you can use pygrib. Or you can refer to the ECMWF recommendations on reading grib files. I'm a little unfamiliar with satellite-derived products, so I can't really help you there.


Are the water year/hydrological year different around the world? Following the commonly-known USGS definition of Water Year (or Hydrological Year) we know that it starts on the 1st October and ends on the next 30th September.

Is this definition valid only for temperate/mid-latitudes?
What's the water year e.g. in the Equatorial, Polar and Arid regions?

Can I keep using the USGS definition for these areas or shall I just use the calendar year (1st January-31st December)?

Thanks

The water year does vary depending on the region, for example in Australia the water year begins on July 1. I am not sure about other regions, I believe the October 1st water year is quite standard across the northern hemisphere although may shift as you go far north to polar and more arid climates. I would recommend searching for similar links to the one for Australia to find the government defined water year, if it exists in your region of interest.

The purpose of the water year is to use, in lamens terms, the least exciting hydrologic time of year to avoid missing large events or fluxes based on the start time of simulation or data consideration, so depending on the annual hydrologic patterns in the given region shifting the water year start generally makes sense. For this reason as well, the calendar year is generally a bad idea for hydrologic models or data considerations, since you are then starting during a time of accumulated snowpack and can have mid-winter melts around that time (at least in the northern hemisphere, generally speaking).


What is the percentage of the global water cycle (evaporation, precipitation) that occurs over the ocean? Most of the water cycle studies focus on the processes and changes occurring over land with little emphasis on the ocean. Meanwhile, the ocean covers almost 3/4 of the surface of Earth. How much of the global precipitation and evaporation takes place over the ocean? Is it 75% of the total? If the percentage is higher, why does that occur?

The bulk of the planet's precipitation falls from convective storms that develop throughout the Intertropical Convergence Zone (ITCZ). The ITCZ transits north and south of the equator due tracking the sun's zenith throughout the year and is skewed by the position of land, but is generally situated near the equator over the ocean.

Trenberth et al (2006) go into detail describing the different components of the global hydrological cycle, but the core of their research can be summed up in the image below.

~96.5% of the world's water is held in the oceans.
~90% of evaporated ocean water leads to precipitation over the oceans.
~77% of precipitation falls over the ocean.
~10% of evaporated ocean water leads to precipitation over land. This equals the roughly ~10% of runoff that returns to the oceans.
Envirotranspiration from plants plays a noticeable role in the water cycle over land.

Personally, I do wonder about the ~77% falling over the ocean.  That number seems a slight bit low given recent remote sensing data of global annual precipitation.


Why is it necessary in seismic imaging to calculate an image of reflection coefficients when one of the inputs is the velocity model? Note: I'm not at all an expert in this field.

I read in the first few pages of Robein (2010; Seismic Imaging, A Review of the Techniques, their Principles, Merits and Limitations, EAGE) that both seismic imaging techniques, time and depth migration,

  require an estimate of how fast the seismic waves travel
  at any given point in the Earth

But it seems to me that the velocity model would be good enough as an image of the underground and performing excessive processing of the data could mar the quality of the image produced.

Input Marmousi velocity model (already a good image of the underground)

Output Marmousi image

One of the inputs to seismic processing is a guess at a low-resolution velocity model that is just good enough to build an image. It is not a geologically useful model of acoustic velocities in the earth.

That Marmousi example is a bit misleading, because that seismic section is a synthetic seismogram, simulated from that velocity model (and assuming or modeling rock densities — we need velocity and density to get rock impedance). It is a result of solving the so-called forward problem$\dagger$ — solving a system of equations representing the seismic experiment, shown here as G, given an earth model m, and getting synthetic seismic data d:

Geophysicists spend most of their time trying to solve the inverse problem — deriving an earth model m (which is the interesting unknown), given real seismic data d (which we measured), and the parameters of the experiment, our understanding of nature, etc (G). So in a real problem, we wouldn't know that high-resolution velocity model a priori.

So what was all that about 'requiring an estimate'?

We don't go straight from the data to a high-res earth model. First, we have to build a seismic image, via a process called migration, which requires us to guess a rough velocity model to focus all the seismic energy into something we can interpret. We do this by choosing a grid of velocity-vs-depth functions that seem to focus well.

Here's a pretty typical velocity model for imaging, from a Marmousi example by Tristan van Leeuwen (2012; UBC preprint). Notice how it lacks high frequencies:

Once we have an image, interpreters and seismic analysts can use various methods to reconstruct a plausible model of the earth's impedance. This is called seismic inversion, and is a substantial area of research. It will almost never result in a model with the resolution of the Marmousi model, but we'd like it to be good enough, over enough of the stratigraphy, to be useful.

$\dagger$ Forward models are useful because we can try to figure out ways to solve the inverse problem better when we already know the answer. Inverse problems are useful because they are a systematic way of making data-constrained inferences about unknowns. Here's some reading on forward and inverse problems:

What is inversion?
How to get paid big bucks
Backwards and forwards reasoning


What will happen to the Indian plate after it slides under the Eurasian Plate? What will happen if the Indian Plate is done sliding under the Eurasian plate? I hypothesied some possible answers. Tell me the answer and if my hypothesis is not correct.
Most likely to least.
It will become part of the Eurasian Plate?
It will slide back out of Siberia?
It will get pushed into the mantle?
I know it is funny to think that the Indian Plate would find its way out of Siberia. I would also want to know what would happen to Mount Everest and the Himalayas.

It is a continent-continent collision following subduction, no subduction is taking place at the moment. The ocean floor that was attached to it has vanished into the mantle or got wedged into the thickened crust. The collision builds up immense stress, resulting in deformation, faulting, folding, crustal shortening and uplift of the Tibetan plateau.
https://www.files.ethz.ch/structuralgeology/jpb/files/English/Asiaeng.pdf
Will it become part of the Eurasian Plate?
That's a question of definition of plate boundaries, fault lines, sutures ...
Will it slide back out of Siberia?
Of course not. How could rocks even be preserved in such a process? In the process of shortening the crust is near completely consumed.
Will it get pushed into the mantle?
No. Continental crust doesn't subduct. Both sides have approximately equal density and the mantle is much denser, so they just push and shove each other. Maybe parts get pushed to greater depths (~100km) in the dynamic process and exhumed again. Shortening will continue, uplift, faulting, folding and erosion in equilibrium, and when and where uplift stops erosion will take over.
Afterwards there may probably be something like the Appalachians, an older result of a continent-continent collision and a very thick continental crust. Pop-science link depicting the principle: https://www.nps.gov/subjects/geology/plate-tectonics-collisional-mountain-ranges.htm


How important is Sahara dust for the Amazon? A recent article by Yu et al. estimated that 28 million tons of dust from the Sahara fall to the surface over the Amazon basin per year out of the 132 million tons that remain in the air when the dust reaches South America. The deposited dust is rich in phosphorus and contributes 22,000 tons of P per year, which is about the same amount lost from rain and flooding. The question is: how important is this phosphorus to the biological production of the Amazon basin? Also, considering Yu et al. reported very large interannual variability, do we expect to see any variability in the production at annual to decadal scales?

Lovett (2010) describe that as the soils in the Amazon Basin are actually nutrient poor, due to nutrients such as the phosphorous and iron supplied by the Saharan dust, being leached out via the higher rainfall.  The Saharan sediment is rich in nutrients as, according to Lovett (2010), it is essentially dried up lake bed sediments, mostly (56%, according to Fisher, 2007) coming from the Bodélé depression in Chad, Africa, which is composed of diatom shells which have significant (but not excessive) amounts of phosphorous and iron - this is a finite source.

Mahowald et al. (2014) explain that phosphorus availability constrains both carbon uptake and loss, hence, the amount of phosphorus in a forest is a limiting factor for rainforests (and other environments).  Atmospheric phosphorus, such as that from the Sahara is linked with the long term productivity of the Amazon.  Mahowald et al. also state that biomass burning is also a source of aerosol phosphorus.

In terms of variability, Lovett also explains that these plumes are seasonal - during summer, they go across the Caribbean and winter, traversing south to the Amazon.  It is believed that at current rates of dust dispersal, this nutrient input could last for another millennia - however, there is considerable uncertainty due to uncertainty in the climate models about the Sahara becoming wetter or drier in future.

If drier, Lovett asserts that there would be more dust, allowing the continued input to the Amazon, whereas increased precipitation, i.e. a wetter Sahara would result in less dust, hence less nutrient input to the Amazon.  Miller et al. (2014) explain that many climate models predict that enhanced dust aerosol loading would reduce precipitation due to the dimming effect reducing evaporation, hence making the environment drier.  However, aerosols, including dust, are a major source of uncertainty in climate modelling.

Anthropogenic activity is also a significant source of uncertainty in long term climate modelling, it is suggested by Mahowald et al. that current land use changes in the Amazon itself is having a significant effect on the phosphorus input in the Amazon and surrounding forests.

A generalised view of the phosphorus cycle is provided below (from Wikipedia):

For the Amazon, the important differences are that atmospheric deposition is a vital input, and that leaching and runoff are more important loss mechanisms. (Crop harvest is also relevant due to human activity in the basin).

References

Fisher, 2007, Amazon forest relies on dust from one Saharan valley, New Scientist

Lovett, 2010, African dust keeps Amazon blooming, Nature News

Mahowald et al. 2014, Impacts of biomass burning emissions and land use change on Amazonian atmospheric phosphorus cycling and deposition, Global Geochemical Cycles

Miller et al. 2014, Impact of Dust Radiative Forcing upon Climate, Mineral Dust