What is the difference between vertical turbulent entrainment and turbulent diffusion in the ocean? In analyses of mixed layer heat budget analysis, authors of different papers have considered the contribution of vertical mixing in different ways.

Halkides and Lee (2011) have considered entrainment, vertical advection and vertical mixing as components of subsurface processes indicating that entrainment and vertical mixing are different processes.

Foltz et a. (2010) on the other hand explain that turbulent entrainment and turbulent diffusion are processes involved in vertical turbulent mixing. This paper indicates that entrainment is a part of vertical turbulent mixing.

Please explain the difference between entrainment and vertical mixing if at all they are different processes.

I would say that different authors might want to distinguish deep convective mixing with entrainment from purely diffusive or gravity wave-driven mixing. Deep mixing occurs mainly within certain zones (around Antarctica, and in the Labrador sea) because it requires a very strong cooling of the surface to trigger convection. Diffusive or gravity wave-breaking mixing can occur anywhere. Diffusion could include direct processes (like double-diffusion or "salt fingering") or indirect processes such as cabbeling or thermobaricity. If their budgets are based on models, these classes of processes are likely output separately anyway, so it's an easy division to make.

I would break it down as follows, with an eye toward model output:

Vertical advection comes from the advection by resolved or implied vertical velocity. This would include Ekman pumping and any other vertical velocity you might get from an omega-equation.
Entrainment-detrainment comes from convective processes. These require special handling, since many ocean models until recently would not resolve these processes. (They might occur in areas that are only a few kilometers in width, far below the lateral resolution.) These processes can mix together entire parts of the water column at once and often do not care about vertical gradients; they are "non-local".
Diffusive processes are very local/small-scale and depend on vertical gradients of heat and salt. Cabbeling, thermobaricity, and double diffusion are some examples. I include gravity wave-driven mixing here because although the gravity wave generation process is non-local, when they break they can only mix locally within the water column.

This kind of breakdown makes sense for a global ocean model, where these three things are handled by three separate modules. For super-hi-res regional models and non-hydrostatic models, advection and convection start to merge together, and if the model is truly eddy-resolving, entrainment becomes a mix of advection followed by diffusion. How you budget these processes depends on the spatial and temporal scales of the model.


Seismic Reflectivity and Fractal (Random) Behavior *One of the fundamental assumptions of the convolutional model (and subsequently a lot of deconvolution methods) is that reflectivity is a purely random (or "white") process. Overall, the only predictable part of a seismogram is that of the source wavelet. Now, reflectivity is NOT purely random. Despite this, the convolutional model is still a very useful tool.

-My question(s) is this: what if reflectivity is somehow predictable? What would that (for lack of a better word/phrase) look like? How would that jeopardize the usefulness of different deconvolution methods...? Thanks in advance to anyone who can help clarify this.

The assumption that the earth's reflectivity is random (i.e. has a white spectrum) is only necessary for the statistical extraction of a wavelet from the data itself via the amplitude spectrum of the autocorrelation function. The convolutional model still works regardless of the reflectivity pattern, although getting a wavelet may be more difficult if the "white reflectivity" assumption does not hold.

On the other hand, in most sedimentary basins, earth's reflectivity pattern tends to not be random. Sedimentary deposition happens in nested cycles forming smaller cyclic layers within large cycle layers. This fractal nature is observed in the amplitude spectrum of real (i.e. measured) reflectivity series. Instead of a having a flat (i.e. white) amplitude spectrum, real reflectivity series tend to have low amplitudes in the lower frequencies and high amplitudes in the high frequencies (i.e. blue) while generally conforming to a consistent positive slope line when ploted in octave vs dB. The slope of this line is a characteristic of the local geology and contains information about the fractal nature of the layering.

This concept is used in a technique called spectral blueing (and also similarily in coloured inversion), where seismic data is forced to match the characteristic reflectivity amplitude spectrum line causing an increase in apparent bandwidth.


How is the Rossby Radius used to determine that synoptic weather systems are 1000-2000km across? In one of his presentations, Sandy MacDonald (of NOAA and ESRL) talks about the Rossby Radius of Deformation in connection with the size of synoptic weather systems: he describes how it sets the diameter of "large-scale" systems to be 1000-2000 km across, so that if we want to even out meteorological effects, we need to consider areas with diameter larger than that.

How is the Rossby Radius of Deformation used to determine that scale of 1000 - 2000 km?

The Rossby radius of deformation ($\lambda_{R}$) is a length scale over which  adjustment will occur while a system approaches geostrophic equilibrium.  In my class noted I have this defined as the distance at which buoyancy becomes as important as rotation.
Some examples are given here but do not show their derivation.

The distance that cold pools of air can spread under the influence of the Coriolis force.
A cold pool will initially spread out toward and under warmer air because of higher pressure under the cold, denser air. However, as the spreading velocity increases, the Coriolis force will increasingly turn the velocity vector until it is parallel, rather than perpendicular, to the pressure gradient. At this point, no further spreading will occur and the winds will be in geostrophic equilibrium. The final equilibrium distance traveled by the edge of the cold air equals the external Rossby radius of deformation, $\lambda_{R}$:
$$\lambda_{R} = {\sqrt{(gH\Delta\theta/\theta_0)}\over f_c}$$

I'm not familiar with the particular derivation used to come up with the 1000-2000 km $\lambda_R$ for synoptic weather patterns but it likely starts with Rossby waves and a wave solution for their propagation.
One example derivation for $\lambda_{R}$ I can think of is in a shallow water model in a rotating frame from Holton (2004) p 211.  In his setup he starts with the height ($h'$) of his shallow fluid with a discontinuity along $x$ defined as $h' = h_0 \mathrm{sign}(x)$ where sign($x$) is the sign of x.  As the fluid equilibrates, the heights will change at the discontinuity and at some distance from the discontinuity.  How far away?  That is what the Rossby radius of deformation tells us.  For Holton's shallow water model, he finds $\lambda_{R} \equiv f_0^-1\sqrt{gH}$ where $f_0$ is the Coriolis parameter, $g$ is gravity and $H$ is the mean depth of the fluid.  At distances less than $\lambda_{R}$, we will observe the height changes but further than $\lambda_{R}$ we will not notice any changes in fluid height.  In this case we can interpret the Rossby radius of deformation as the length scale over which the height field changes during geostrophic adjustment.


Does the length of a river depend on the scale of measurements? Coastlines are highly fractal, leading to the coastline paradox: the length increases to surprisingly large numbers as your scale of measurement gets smaller.

Does the same thing apply to rivers, or is there some mechanism that keeps their lengths reasonably finite?

The same problem applies to all shapes that are complex and this includes coastlines, rivers and the perimeters of leaves. Most shapes derived by nature will have this issue. The unit of scale matters.

Only shapes that are composed of straight line segments and can be easily measured as such do not have this problem: triangles, rectangles, hexagons, etc. Such shapes are mathematical or created by humans.


Are 'Return Periods' being recalculated? If so, how? The concept of 'return period' (= 'average recurrence interval', or ARI) is widely used in hydrology, and to a much lesser extent in geology, geomorphology, geophysics, etc. Whatever the application, the traditional analysis is predicated upon 'stationarity of the data-set'. However, in this new era of climate change the hydrologic data set is, by definition, no longer 'stationary'. That is, the underlying statistical parameters are no longer consistent. Therefore, a new methodology is required to take account of the drift in climatic means, extremes, revised frequencies, etc. Are there any first attempts to deal with this problem?

One possible example could be the study of ice cores in Antarctica where scientists are trying to determine changes in concentrations of gases like carbon dioxide over a period of time . Such variations serve as indicators for other Climate related factors such as Temperature.

This record was a key contribution to climate science. One, it revealed how past CO2 levels compared to past temperatures. And since the data was directly derived from air bubbles trapped beneath hundreds of feet of ice, it also provided us with an exact measure for past atmospheres.

Secondly, and perhaps much more ominously, it showed us how very far beyond any climate comparable to that great span of time we’d already come.

102 ppm higher than at any time in the last 800,000 years

Humans have now pushed the CO2 boundary 102 parts per million higher than the context provided by the last 800,000 years. It’s kind of a big deal when you consider that a mere fluctuation of about 100 parts per million CO2 was enough, when combined with changes in orbital forcing, to set off feedbacks resulting in a 4 C temperature change globally (8 C change for the Antarctic environment) as ice age proceeded to interglacial and back.

source : World CO2 Averages Touch 402.2 PPM Daily Values

Further read : Links between atmospheric carbon dioxide, the land carbon reservoir and climate over the past millennium


Why does Mars' experience an 'ice age' at high axis obliquity, when Earth experiences an ice age at low axis obliquity This paper here goes into some detail about how Mars' experiences its own form of 'ice ages' on a quasi periodic basis driven by the wobbling of its axis. The main mechanism outlined is that the stability of water ice on the surface increases with increased obliquity. This is in contrast to Earth when at high obliquity there is increased polar summer insolation leading to metling. What is the difference?

On a more discussion based addition to the question, could factors such as ice albedo and other feedback loops play a similar role in Mars' ice ages that they do in Earth's ice ages?

I have also asked this at the Astronomy stack exchange here

If I understood it correctly, the important point is the temperature difference between mars and earth. On earth increasing obliquity, as you wrote, leads to increased melting of ice, ie. you increase the amount of liquid water on earth.

On mars average temperatures even during summer are too low to allow for liquid water. Higher obliquity doesn't really lead to a melting of ice. It mainly increases sublimation thereby increasing the water content of the atmosphere also on lower latitudes. The water vapour freezes out and leads to ice shields extended to lower latitudes.

So in short, since temperatures on mars are too low to allow for liquid water, the extend of the ice cover is larger, when the ice receives increased insolation.
Whereas on earth the ice cover is larger when insolation is low, since it gains mass from the pool of liquid water.


What can I use as a heatproof, non-magnetic glue for samples? I, and many of my palaeomagnetist colleagues, often use thermal demagnetization (potentially up to 800°C) in our studies. Usually a stepwise technique is employed, so each sample is heated -- often 20 or more times -- to progressively higher temperatures. This can become a problem with jointed or friable samples: the pieces have to be glued together in order to make a measurement, but there are very few adhesives which are both heatproof and non-magnetic. By ‘non-magnetic’ I mean that it should carry as little remanence as possible; while it would also be nice if it had a negligible magnetic susceptibility, this is a less important factor.

In my search for an adhesive which is heatproof as well as non-magnetic, I've looked at:

UHU. Good bond, non-magnetic, but not very heatproof. Even the high-temperature version breaks down at about 250°C. Beyond that, every heating step leaks noxious burning-glue fumes into the lab and I have to re-glue all the samples before measuring them.
Cyanoacrylate (a.k.a. superglue). Non-magnetic, and bond usually OK, at least on fine-grained rocks. Even less heat-tolerant than UHU, but the fumes are a bit less noxious at least.
Aremco Ceramabond 571, a magnesium oxide based paste which easily fulfils the temperature requirement (it's rated to 1760°C) and was recommended to me as non-magnetic (albeit not by the manufacturer). Unfortunately it turned out to carry a significant mangetic remanence, and contaminated measurements unacceptably. (It might work reasonably for strongly-magnetized volcanic samples, though.)
Sodium silicate in aqueous solution, a.k.a. water glass. Magnetically, this fits the bill. Kostadinova et al. (2004) reported that it doesn't appear to affect remanence measurements (although it does alter susceptibility). It's thermally stable up to the temperatures I care about and beyond. With clay-rich material I had some trouble with expansion (intumescence) of treated samples upon heating and have heard from other researchers that this is a known problem; Otaka et al. (2002) indicate that heating rate is also a factor. Another problem is that the adhesive properties are not ideal: sodium silicate works well as a binder for soaking and impregnating loose, friable material, but doesn't make a good contact adhesive for less porous rock.
Automotive silicone adhesives: I have seen various silicone adhesives designed for work on automotive exhaust systems. They would probably fulfil the temperature and adhesive requirements, but I haven't yet done any pilot studies on their magnetic properties. Given the intended applications, there's no reason for the manufacturers to specifically exclude magnetic compounds from the mix. I'd be interested to hear if anyone's tried any adhesives of this sort.

I should add that the adhesive requirements are actually very modest: the join doesn't have to bear any load beyond the weight of the sample itself, which will not exceed 50g.

References:

Kostadinova, M., Jordanova, N., Jordanova, D., & Kovacheva, M. (2004). Preliminary study on the effect of water glass impregnation on the rock-magnetic properties of baked clay. Studia Geophysica et Geodaetica, 48(3), 637-646.
Otaka, T., & Asako, Y. (2002). Thermal intumescent characteristics of heated sodium silicate. In ASME 2002 International Mechanical Engineering Congress and Exposition (pp. 205-210). American Society of Mechanical Engineers.

Oxford Instruments used to sell a VSM (vibrating sample magnetometer) with an oven option up to 1000K. Mounting samples was made using a "non-magnetic" paste/cement. You may want to look into that.


How do cations control the crystal structure of silicate minerals? Beyond the obvious fact that in many of the silicate subtypes they play an ionic 'glue' like role by bonding the tetrahedra units together; how do cations control the structure of a silicate and how does it vary between different cations and silicates?

I would say that cations would control the structure in several ways; in the case of aluminum octahedra in aluminosilicates, for example, they might completely influence it by causing the presence of completely separate alternating layers of bonded octahedra. The octahedra may even dominate the unit-cell, appearing in a larger numerical and volumetric capacity than the tetrahedra.

Additionally, the different bonded cations have different polarities, and by extension, exert different forces on the relevant bonds; this plays a huge role in determining how the structure responds under conditions of high pressure relevant to the Earth's interior, e.g determining where shearing takes place, etc.


If 75% of radioactive material remains, how many half-lives have elapsed? Radioactive element A radioactively decays into material B. If 75% of A and 25% of B are present, how many half-lives of material A have elapsed?

I was recently taught that the correct answer is "one half of a half-life has elapsed". However, due to the fact that the amount of radioactive material remaining scales exponentially (logarithmically) instead of in a linear fashion, wouldn't the answer be less than one half of a half-life?

@gerrit provided a formula, but without stating the reasoning behind it.

Radioactive decay is an exponential function.  After $n$ half-lives, the amount of the original material remaining is

$$\textrm{amount remaining after}\ n\ \textrm{half-lives} = \left(\frac{1}{2}\right)^n$$

Therefore, you want to solve

$$\begin{align*}
\left(\frac{1}{2}\right)^n &= \frac{3}{4}\\
\log_\frac{1}{2} \left(\frac{1}{2}\right)^n &= \log_\frac{1}{2} \frac{3}{4}\\
n &= \frac{\log \frac{3}{4}}{\log \frac{1}{2}} = \frac{\log \frac{3}{4}}{- \log 2}
   \approx 0.415
\end{align*}$$


Is Ozone Layer a Valid Concern I’ve had a simple puzzlement concerning the ozone layer.  Succinctly, the troposphere is largely and preferably ozone free.  When it thermally rises at the tropics to become the stratosphere molecular oxygen cleaves under actinic radiation to from nascent oxygen that, in turn joins with molecular oxygen to form ozone.  The stratospheric ozone, of course, is vital to protect against harmful radiation.  Then at the polar vortices the flow once again returns to the troposphere.  Ozone is undesirable in the troposphere and is removed at this point.

If this is accurate (?), why would halides that disassociate ozone (in conjunction with ice crystals only present at the Antarctic pole) be seen as adverse?

Every time the rays of the sun come into contact with earth they have to first be reflected back to the ozone layer before returning to earth. This has a cooling effect on the earth temperature. Since the industrial revolution the ozone layer has been severely depleted by the greenhouse gas emissions. Remember the sun is a ball of burning gases, whose light reaches earth early morning within eight minutes. If the earth just moved an inch away in space from the position set approximately from the sun, earth could freeze and no living organism would survive. In the same regard if it moved an inch closer to the sun every life would be incinerated.


Highest land altitude a tsunami has ever reached (record) When a tsunami gets into the coast we are approximately at 0 meters above average sea level (AASL). And then it starts ascending in the uphill land... 1m AASL... 2,3... 5,10 m AASL etc.

That is exactly my question. What is the highest altitude a tsunami has ever reached? Maybe it always remains in low level, like 10 or 15 meters above average sea level or there are records about 40-50 meters? Is there a confirmed record? Records after renaissance or ancient Greeks, Egyptians, Chinese etc could be considered reliable?

PS: I am not talking about its height while it is in sea or when it crashes the coast. I am talking about the highest land altitude that a tsunami has ever reached much later after its crashing in coast.

PS2: I understand that my question is not clear and it has vagueness, so i will try to clarify it. Every point in the surface of Earth has coordinates (with respect to North and East). And each unique point has an altitude. Two examples: a) The point with coordinates 27.9881° N, 86.9250° E has altitude 8848 meters. It is Everest's summit. b) The point with coordinates 36°34′N 21°8′E has altitude - 5267 m. It is Calypso Deep, the deepest point of Mediterranean.

So, my question, i look for a specific point on the Earth with the maximum altitude A and coordinates B North and C East in which the sea water has ever reached (lets focus on relatively recent years after renaissance). As I understand this can happen only by phenomena like big waves or tsunamis. There is no something else. So where is this point and what is its altitude? In that case, we dont care about the height or the momentum of the wave. Also the accuracy is not so important... Just an idea "when a tsunami climbed a mountain".

About Lituya Bay in Alaska... There is a mountain there: Fairweather with altitude 4671 m... So the tsunami in 1958 ascended 524 m in this mountain? Why i think it didn't even pass 100 m altitude? The height of a wave is completely different and independent with the highest altitude it finally reaches.

The worlds highest recorded tsunami occurred during a landslide triggered by an earthquake in 1958 in Lituya Bay, Alaska. The landslide sent the water 524 meters high the other side of the valley and left its contours in the vegetation. According to whitnesses, it lifted a glacier tip above the surrounding mountain tops.

https://geology.com/records/biggest-tsunami.shtml

https://earthquake.alaska.edu/60-years-ago-1958-earthquake-and-lituya-bay-megatsunami

I think this was the highest run-up on records (let's see if i get topped). But there probably occurred higher ones in earth's history. Candidates are asteroid impacts (e.g. Chicxulub) or flank collapses on volcanic islands.


What are the relative contributions of planets to the Milankovitch Cycles? When reading about the Milankovitch cycles here, it says:

If the Earth were the only planet orbiting our Sun, the eccentricity of its orbit would not perceptibly vary even over a period of a million years. The Earth's eccentricity varies primarily due to interactions with the gravitational fields of Jupiter and Saturn.

My question is, what are the relative contributions of Saturn and Jupiter to the orbital eccentricity of the Earth?  Do the Trojan Asteroids also factor into the eccentricity of our orbit?  Finally, what is the temperature change we can expect on Earth due to changes in eccentricity of Earth's orbit around the sun (e.g. the long-term climate cycle)?

The tidal effect over time tends to circularize orbits.    It's well known that Moon is being tidally pushed away from the Earth over time (about 1.5 inches a year).  This effect is stronger when the moon is closer and weaker when the moon is farther, so there is a very gradual tidal circularizing of orbits over time, unless the orbit is highly eccentric, then you can get the reverse effect, if, when the orbiting object accelerates ahead of the tidal bulge during Perihelion that can draw it closer to the sun during that part of the orbit and that tidal effect tends to increase eccentricity.

This tidal "circularizing" only works in 2 body systems though.  3 body systems and n-body systems are more complicated.  I can't explain the effect of Jupiter and Saturn because 3 body gravitation is too complex, but I can tell you that Trojan asteroids and the asteroid belt are not factors or, very very tiny factors because they don't have enough mass.  orbital cycles are all about the strength of the gravitational fields any synchronization of orbits.  The gravitational fields on Earth by the asteroid belt or Jupiter trojans is too tiny.

The temperature change on earth can be observed by the ice ages.   The net effect of the Milankovich cycles, if the earth was consistent would be quite small, maybe 1 degree C peak to trough.  Most of the 10 degree change globally that we see, ice age to warm period between ice ages is due to feedback mechanisms on the earth, glacier formation and ice cover increases albedo which reflects more sunlight directly back into space and colder oceans absorb more CO2 which lowers the greenhouse effect and as glaciers grow high the air over high altitude gets colder.   Changes in ocean currents may be factors too, but that's not as well understood.

Locally, the effect can be much greater than 1 degree C though, even without the feedback mechanisms.   Precession has much more significant local effects because 3.4% closer at Perihelion means 6.8% more energy, and that's significant, even if it varies,  3.4% above normal peak summer to 3.4% below normal, low winter, but that's enough to cause a significant change.   It's thought that precession is behind the Sahara desert cycle between forest and desert every 13,000 years or so.   Precession may be (speculation on my part), a factor in ending ice ages as well, but it doesn't seem to be a factor in starting them, as ice ages appear to begin on roughly 100,000 year cycles and before that, 40,000 year cycles.   Source.   There's not any good evidence that I know of for ice ages operating on 26,000 year cycles.


Is there evidence of multiple poles (higher order than dipole) in earth's magnetic field? There is this slightly uncombed simulation model of a geomagnetic field reversal, showing multiple poles, a quadrupole or even higher order magnetic field. Earth's magnetic field is mostly described as a dipole and navigation wouldn't work without that, (considerable) local perturbations left aside. But a multipole field is a theoretically valid configuration, as long as no N or S pole remains solo (quadru-, sextu, octupole ...). Some bodies in the solar system may have multipole fields.

But for earth's magnetic field, is there actual evidence of multiple poles at a time, from geomagnetic chronolgy, ocean floor or ophiolites, magma flows ? These may be transient events, happening during reversals.

It's common for dynamo models to predict a large reduction in the dipole field during a reversal. Proving it in the paleomagnetic record is another matter entirely. To characterize the geometry of the magnetic field, you need several simultaneous measurements, preferably with a good spatial distribution. Instead what you get are relatively infrequent, asynchronous measurements. See this article by Fabio Florindo for more details. For what it's worth, though, a model by Olson et al. (2011) with multipolar fields during the transition predicts some observations that are consistent with the Matayama-Brunhes transition, including reductions in the intensity of the field and variations in the virtual geomagnetic pole path (VGP) from one site to another (see page 124 of this book for a definition of a VGP).


How are CO2 emission effects and high altitude effects of air travel compared to each other? The climate impact of air travel is often divided into CO2 emissions and "high altitude effects" like that of water vapour and cloud formation. The effect of the emitted CO2 is cummulative, as CO2 has a high retention time in the atmosphere. On the other hand, as I have understood it, the high altitude effects are more short lived. Their impact on temperature are determed by current levels of air travel, and not past.

How can the size of these two effects be compared to each other or to other sectors such as travel by car? Is there any videly accepted method for this? It seems a bit like apples and oranges to me.

I know about GWP, that uses a somewhat arbitrary timeframe of 100 years. Is and can that be used here? I have also heard about RFI, but I am unsure how that works or is applied to this.

The CO2 is a greenhouse gas which causes a net heating effect as it retains additional solar radiation, the exact magnitude of this effect is still highly debated. The high altitude effects you've mentioned are often referred to as "jet exhaust shading" and it's estimated, based on some temperature data from the week after the 9/11 attacks in the US, that it causes roughly 4°C of cooling, this is because the jet exhaust contains water which condenses out as high albedo clouds, and sulfur compounds that absorb solar radiation as well as the CO2.


In what geological situations can I find gold? I've heard that gold ore is often associated with quartz veins.  What geological processes enable gold particles to naturally cluster together like this? What characteristics/properties should I look out for on the surface of a rock that are likely to yield gold within it? Are there remote sensors that I use to detect the presence of gold in a rock?

I think Azzie's answer describes the situations where gold is formed and found as Lode deposits. But native gold in lode can then be subject to weathering when it is exposed, which releases the gold into the environment as flakes, grains and nuggets. This gold is then subject to erosive and sedimentary processes.

As gold is denser than most minerals it can often be concentrated by sedimentary processes as Placer Deposits, where the gold is concentrated by gravity. Dense gold quickly settles out of a water column, and lighter minerals are winnowed away. These accumulations of gold can then be economically mined using Placer Mining techniques such as Gold Panning. The Witwatersrand Basin in South Africa is an important palaeo-placer deposit from which nearly 50% of all of the gold ever mined has been obtained.

Alluvial placers are formed by the deposition of dense particles at a site where water velocity remains below that required to transport them further.Typical locations for gold placer deposits are on the inside bends of rivers and creeks, in hollows, at the break of slope on a stream or the base of an escarpment, waterfall or other barrier.

The vast majority of the Earth's gold and other heavy metals are locked up in the Earth’s core, being a dense material most of the gold is thought have sunk to the centre of the Earth as the core formed. Though there is 1000 times more gold in the Earth's silicate mantle than would be expected. Evidence from tungsten isotope studies indicates that most of the gold in the mantle and crust (which we can access) is derived from gold which arrived during the Late Heavy Bombardment some 3.9 billion years ago.(BBC Article 1) Which has been called the Late Veneer Hypothesis.(BBC Article 2)

Future mining of asteroids for gold and other metals has been proposed,(Reuters Article) with estimates that there are up to 20,000 million tonnes of gold in the near-Earth asteroid Eros, with an estimated value of $1,000 billion (1999).(BBC Article 3)


What exactly are singular biomes as units? So let's take the tropical rainforests of Earth for an example. The Congo, Amazon, Indonesia, Malaysia, and wherever else it may grow. Are all these aforementioned places considered parts of one biome, the tropical rainforest? Or are the Amazon Congo and etc. all just considered their own biomes which just happen to share the same biome type (in this case the tropical rainforest)?

I guess it depends on which biome classification you use (there are several), but yes, usually tropical forests of Amazonia, Africa & Asia are classified within the same biome. For instance if you take the WWF classification made by Olson et al. (2001), which has 14 terrestrial biomes, they all fall in the "Tropical and subtropical moist broadleaf forests" biome, in green in their figure 1:

The ecoregions are categorized within 14 biomes and eight biogeographic realms to facilitate representation analyses.

It means they share some global characteristics in terms of climate, vegetation... (described here), but they also have some differences. To see these differences, you have to go to a lower level than biomes: ecoregions. The same study divided the world into 867 ecoregions, that are mostly based on the distribution of species.


What is trace-based seismic Inversion Looking through different literature articles and books concerning seismic inversion - mostly post-stack - phrases like "trace-based" and "model-based" keep appearing. I know that model-based in when lower-frequency info from either stacking velocities or low-pass sonic/rho logs are used. However, I do not know what trace-based inversion means or how it's performed. Can someone please help me with this?

I too have found this nomenclature rather confusing.  I am pretty sure that trace-based inversion is merely where each seismic trace is inverted independently of surrounding traces. This would take into account most deterministic/probabilistic inversion types (e.g. model, coloured, sparse, etc). In contrast, geostatistical inversion would not strictly be trace-based inversion, as it uses a spatial and temporal variogram to takes into account the expected results of surrounding traces during the inversion, even though it does invert on a trace-by-trace basis. Confusing.

The following paper describes trace and geostatistical inversion methods:
Germán Merletti, and Julio Hlebszevitsch. 2003. Geostatistical Inversion for the Lateral Delineation of Thin Layer Hydrocarbon Reservoirs: A Case Study in San Jorge Basin, Argentina. SEG 2003.

I've found the following paper very useful for understanding seismic inversion (geostatistical isn't discussed, though):
Dennis Cooke and John Cant. 2010. Model-based Seismic Inversion: Comparing deterministic and probabilistic approaches. CSEG Recorder, Vol. 35, No. 4.


Why rely on climate models as opposed to paleoclimate data? Something I hear often from climate scientists, and indeed even politicians, is that we "don't understand climate change very well". And, I'm sure this is true since the climate is a complex adaptive system with thousands of dependent variables, one that we don't yet have the computational sophistication to accurately model. But that doesn't mean we don't know, to a high degree of accuracy, what is going to happen if we make certain changes to the atmospheric composition or take certain actions. We have paleoclimate data ranging extensively far back many hundreds of thousands of years, encompassing global temperature, climate cycling, atmospheric composition, and more.

Sure, the global temperature 100,000 years ago wasn't measured using a thermometer, but we've used various independent proxy methods that all agree with each other to a reasonable degree, right? And so do we not then have a reasonably accurate idea of Earth's climate sensitivity by simply looking at precedent? And paleoclimate will be close to exactly right since it takes all the variables into account exactly in the amount they're needed to be accounted for. Why are we still "uncertain" about the realities of climate change? Why are we not moving on and taking decisive action based on this--what seems to me--reliable, accurate data?

We need both paleodata and models, in fact the relationship between paleodata and the climate at a certain time is typically evaluated through models. Paleodata does not actually measure climate observables directly (tempreture/pressure/salinity/other) but instead is (e.g.) a geochemical quantity related to one of those.

For example, the two most frequently used records are the Antarctica EPICA ice core record and the Lisiecki Raymo benthic stack. The isotopes in these records are affected by temperature at a point on the planet and global ice volume, but how that relates to global temperature and the size of individual ice sheets requires inference from climate models.

Further, climate (or earth systems) models can allow us to probe what could happen in addition to what did happen. Current CO2 levels are reaching a point not seen in the ice core record (our most direct records) and so we need increasingly complex models to get a handle on the range of possibilities.


What does a "closed basin" mean in groundwater terms? This answer talks about a "closed basin" that has an outflow to the sea.

I had previously assumed that "closed basin" meant the same as "endorheic basin", but that is obviously not the case. What is a "closed basin" in this context?

An endorheic basin refers to the surface-water flow. The Great Artesian Basin refers to the groundwater aquifer (the artesian part of the name), not the the Lake Eyre surface water basin, which is endorheic. Part of the land area above the GAB is closed with respect to surface water flow. Endorheic basins may or may not be closed with respect to groundwater. In fact they may be closed with respect to water in local groundwater flow systems but open with respect to deeper flow systems.

It is common for endorheic basins to be open to groundwater flow. This can occur in a number of ways. The groundwater flow may only be affected by recharge within the basin and not discharge to surface water bodies within the basin. In the case of confined aquifers, it may be essentially separate and unaffected by the surface water or shallower groundwater in the basin but may flow under the basin and exit the other side. Groundwater can discharge to flow-through lakes. These lakes receive groundwater discharge on one side but recharge the groundwater downgradient.


How do scientists measure the age of old animal remains? The remains of a mammoth were recently unearthed in a Michigan farmer’s field [1]. This find could provide new information on the activity of early humans in the area, experts at the University of Michigan have said.

The remains of the animal, thought to be 11,700-15,000 years old, show “evidence of human activity.” How do the scientists determine this age?

[1]: www.youtube.com/watch?v=jwsCKW8WJm8

Organic material (plants and animals) contains carbon.

Carbon has three main isotopes: carbon 12, 13 and 14. Carbon 14 is radioactive, with a half life of 5730 years.

Carbon 14 is continuously created in the atmosphere by cosmic rays hitting nitrogen. The nitrogen atoms lose a proton when struck by cosmic rays, turning the affected nitrogen atom into an atom of carbon.

The carbon 14 then reacts with oxygen in the atmosphere to create carbon dioxide. Plants taken in the radioactive carbon dioxide along with non radioactive carbon dioxide. Plant eating animals take in the radioactive carbon when they eat plants and meat eating animals take in radioactive carbon when they eat other animals.

When a plant or animal dies it stops exchanging carbon with the environment and it dies with a certain amount of radioactive carbon 14.

By measuring how much carbon 14 is contained in a specimen and knowing the half life of carbon 14, scientists can calculate when an animal died.

Due to the half life of carbon 14 being 5730 years, carbon 14 dating can only reliably be used for dates up to 50 000 years old.

More details about carbon 14 dating can be found here.


Why would there be no hydrocarbons in the Sveconorwegian belt? I've had an inconclusive chat about the Sveconorwegian belt of the Fennoscandian shield, the western parts in particular, and reasons as to why there would not be any deposits of hydrocarbons there. Perhaps someone here can provide a definite answer?

Is it simply that the belt is of primarily Gothian origin, or might there be more to it?

There's a little more to it than its substantial age, but not a lot.

First, a bit of background. We need a few conditions for accumulations of oil or gas:

A kerogen-rich source rock that has been 'cooked' to thermal maturity. Insufficient temperature, or insufficient time, and it's undercooked; if the temperature is too high, or the rock is very old, then the volatiles have all been discharged or cracked. I don't know of any source rocks older than about Ordovician; the best ones are Jurassic in age.
A migration pathway from the source to a trapping configuration, and time for this to have happened.
A structural or stratigraphic trap, such as an anticline, and the geological conditions that have preserved it since filling.
A reservoir rock — a porous and permeable rock. Usually this is a sedimentary rock, though hydrocarbons have been discovered in fractured granites (in Vietnam for example; this is rare).

Only 'conventional' hydrocarbon deposits need all these conditions (sometimes called a 'petroleum system', such as you might find in the North Sea). 'Shale gas' is basically just a mature source rock — we can extract hydrocarbons from it by fracking, for example.

As you might guess from the list of conditions, there are lots of things that can destroy a hydrocarbon accumulation, or preclude its formation. For example, deep burial destroys porosity by diagenesis and compaction. Time increases the likelihood of trap leakage or thermal destruction of volatiles.

So, why no hydrocarbons in the (mostly Precambrian) Swedish-Norwegian shield? Maybe these are the top 3 reasons:

These old rocks never had a good source rock: too old, too little life. A bad start.
They are so old that any source would have been mature hundreds of millions of years ago.
In any case, metamorphosis has destroyed any potential reservoirs, and a combination of tectonism, orogenesis, and exhumation has destroyed any traps.


How likely is it for coastal cities to survive next 40 years? I live in a coastal city myself and I know there are many measures taken to prevent harm for city buildings from sea waters. I'm not aware of all of them and I wonder if modern cities actually have a plan for constantly growing sea level? How long can dams hold the water? Probably groundwater is also a problem (I think sea level may affect amount of groundwater as well) and it slowly erodes everything underneath. Do modern buildings have any kind of protection from this? Were old buildings designed with this problem in mind? How likely is it that investment in real estate in these cities may turn into dust in not-that-distant future (~40 years)
Edit: as it was noted in the comments section, this situation will vary between cities and the question needs to be narrowed down to a single location. I live in St. Petersburg (Russia), so I'd happy to see analysis for this exact place. Thank you

I also live on the coast and have been concerned about what to expect with regard to sea level rise in the near future. The following graph illustrates the observed rise in sea level over the last 30 years:

As you can see from the image, satellite data indicates a linear increase in sea level rise of 3.3 mm per year for the last 30 years. If this trend continues for the next 40 years, we will see an increase in sea level of 133 mm. The real question is whether or not the linear trend will continue or will it accelerate as a result of climate change?
One possible way to look at this is to compare what temperature has done over roughly the same time period to see if there is any indication that temperature change is accelerating. The following image shows three sets of data with regard to temperature:

The data in this image represents observed temperature changes from balloons and satellites and temperature predictions from computer models. The interesting aspect of this image is the balloon and satellite observations track very close to each other while the model predictions of temperature change are roughly 3 times greater than the observations. Another interesting point is that while the temperature is trending upward for the overall duration, there are multiple periods where the temperature is getting cooler.
There is no obvious sign of acceleration in the observed data, but the current climate orthodoxy would indicate otherwise as indicated by the climate models and as a result of increased CO2 in the atmosphere. So the next logical step is to see what the CO2 levels have done over roughly the same period of time.

For the last 30 years the CO2 has increased linearly at about 2 parts per million (PPM) per year.
Just looking at the data, it would appear the 133 mm increase in the next 40 years would be a good conclusion, but again the current climate orthodoxy disagrees because it is believed small temperature increases resulting from increased CO2 is amplified by the positive feedback caused by the additional water vapor in the atmosphere. Water vapor is the most powerful of all greenhouse gases according to the IPCC.
The counter argument to the positive feedback hypothesis is the negative feedback provided by increased cirrus cloud cover when temperatures rise. There is also the issue of the diminishing global temperature effect of CO2 as described by the five studies in the following image:

Although the numbers are different in each of the 5 studies, they all conclude the heat retention of CO2 decreases logarithmically as the concentration increases. Using the question's time period of 40 years, the CO2 will have increased by 80 PPM to approximately 490 PPM which falls within the first level of the above chart. Using the numbers from the last three columns, the increase in temperature from CO2 alone would range from  0.2 to 0.466 degrees centigrade.
One interesting conclusion from this chart is these 5 studies do not agree in the magnitude of the change which would indicate the science is not settled. Another point to be made is while CO2 concentrations increased constantly, temperatures fluctuated up and down over the same time period which indicates there are other factors in play besides CO2. These differences along with the lack of understanding of the effect the negative feedback of clouds are possible explanations of why the computer models fail to accurately mimic the actual temperature observations.
Since the computer models represent the gold standard upon which future temperature predictions are being made and coupled with the fact their predictions to date have been so wrong, it is reasonable to conclude the 133 mm rise is sea level is likely to be an accurate outcome over the next 40 years. If that is the case, then the action to be taken by various coastal cities would depend upon their specific circumstances. As for me, I do not intend to sell my coastal property based on the existing evidence.
Update:
The lowest parts of St. Petersburg, Russia are about 4 m above sea level. If my estimate of 133 mm sea level rise over the next 40 years is correct, then St. Petersburg will not be much worse off than they already are. I would assume the portions of the city that are that low are already having flooding issues during storms or even during high tides.


US Naval Observatory Sunrise/Sunset Data: Blank Sunrise/Sunset Times? The US Naval Observatory has a webpage that allows a user to enter a year and a latitude/longitude pair, and then produces a table of sunrise and sunset times for each day during that year at that latitude/longitude pair:

http://aa.usno.navy.mil/data/docs/RS_OneYear.php

Sometimes, a blank entry will appear where I would expect to see a time.

For example, in the above webpage, if I scroll down to "Form B - Locations Worldwide," enter the coordinates W074 45, N42 16, leave the "time zone" blank, enter "2015" for the year, and leave all other options at their default settings, I get a blank entry for May 03. Can anyone help me to interpret this, or direct me to an appropriate reference?

There is already a symbol for when the sun does not rise and another for when the sun does not set on a particular day.

I get a blank entry for May 03.

The Sun didn't set on Bovinia, New York on May 03 when time is expressed as Universal Time. Sunsets from May 04 to August 16 occur before sunrise. (Also note that August 16 has two sunsets.)

The solution is simple: Fill in the time zone. Ignoring daylight savings time, time in Bovinia New York is offset by 5 hours from UTC.

Another solution is to use a different website. There are better web services than the simple perl-based script used to generate that table.


Is it physically possible to see mountains from 500 km away? Quoting from lecture notes of Andrew young at San Diego State University:

  For less extreme, but very reliable, observations, consider some listed by Commander C. L. Garner of the Coast and Geodetic Survey in 1933 [...] He also credits the 1911 sighting of the Fairweather Mountains in Alaska [highest point is Mt. Fairweather 15 325 ft or 4670 m] from the ship Explorer from the Gulf of Alaska, 330 miles [531 km] away."

Earth’s mean average radius is 3959 miles by a right angled tangent of 330 miles gives a hypotenuse extending well above the surface of the earth of sqrt(39592 + 3302) = 3973 miles. Subtracting the radius 3959 miles gives the drop in the curvature of the earth from the beginning point where the Explorer made the sighting: 13.7 miles, or 72 492 ft.

72 492 ft minus Mt. Fairweather’s height 15 325 ft gives 57 167 ft to spare for a whole mountain range to disappear beneath the curvature of the earth.

What could account for this sighting 'through' the curve of the earth?

I think what was observed is a superior mirage. A superior mirage occurs when warm air overlies a very cold layer of air, aka an inversion. You don't often see a superior mirage in lower latitudes, but they seem to be somewhat common in and near the Arctic regions.With normal atmospheric conditions and taking into consideration refraction, about the furthest one could see a 15,325 foot mountain from, say, a 100 foot high deck is roughly 177 miles, depending on the tide. The only possible explanation is a very strong superior mirage.There are a couple of good articles here and here that describe the conditions necessary:


Are cloudy nights warmer than nights without clouds? I have noticed this winter that nights without clouds (especially when the 12h before the night where not cloudy) were way colder than the cloudy ones.

It makes sense to me because the clouds can reflect the heat (infrared?) earth have accumulated during the day rather than loosing it into the atmosphere (like a kind of blanket). But I could be "swayed" by a confirmation bias here, so here is my question:

Is there a correlation between temperature and cloud, during the night?

Is there a correlation between temperature and cloud, during the night?

Very much so. It's called radiative cooling. Three factors come into play: cloudiness, relative humidity, and windiness. Nighttime radiative cooling is greatest under clear skies, low relative humidity, and light or no winds. The temperature drop (in degrees per hour) can be a factor of more than four greater under conditions of clear skies, low humidity, and light winds compared to that under conditions of thick low clouds and high relative humidity. That increased cooling can make for a significant temperature drop on a long winter night.


What might be causing this rainbow-like effect on the ground? The BBC News article Iceland's Okjokull glacier commemorated with plaque about a dead glacier speaks for itself.

However there is a photo in the article that caught my eye.

It shows mountains in the background and some dry flatland in the foreground. While the foreground is sunlit, some areas are shadowed by clouds, and there is what looks like it could be the apex of a rainbow along the ground with the mountains rising behind it.

Question: What might be causing this rainbow-like effect on the ground?

  Okjokull sat atop the volcano Ok northeast of the Icelandic capital Reykjavik. Photo: JOSH OKUN

This is very unusual and I've never seen it before, though I have seen other rainbow effects such as double and triple rainbows. What they all have in common is a mist of water droplets lit up by the sun. If you have ever seen a dew drop (and who hasn't) you will have noticed that when the sunlight struck it a pretty coloured light came from it. When you moved your head a little, the light changed colour. This is because white light is bent by the water droplet, and the different wavelengths bend to different degrees, so which colour you see depends on the angle of your eye to the dew drop. It's the same with a rainbow, but in this case there are millions of water droplets. It is also the case with the rainbow-like phenomenon in your photo, but instead of being high in the sky, the water droplets are hugging the ground.

So how could this happen? One possibility that occurs to me is that rain fell on hot ground, and quickly evaporated. As it evaporated into cold air, it condensed into water droplets, so you had this fine aerosol hanging low over the ground. Struck by sunlight, the white light was diffracted in the same way as in a rainbow or a dewdrop or the mist from a garden hose.


Does within-canopy wind direction correlate with wind above the planetary bounday layer? Wind above the planetary boundary layer (PBL) tends to be fairly smooth and constant over short periods of time. Below the planetary boundary layer, the smoothness is broken by eddies caused by friction with the land surface. Below the canopy, wind is presumably even more turbulent, and much slower on average. I'm interested to know how the over-all effect of those eddies changes wind direction within the canopy.

How much do eddies between the PBL and the ground disperse wind direction? Is wind direction below the canopy still correlated with the wind direction above the PBL? And does wind speed follow a similar pattern?

Turbulence is a property of the flow, not a physical characteristic of the fluid. Turbulent flows in nature are evolving due to external influences and at present time there are very few evolving turbulent flows which are well understood. The boundary conditions, such as distribution of canopy, geomorphology, all play a crucial role in determining the turbulent dynamics. All turbulent flows are different but they have similar intrinsic dynamics and through statistical means one can relate the properties of the mean flow to the turbulent dynamics.

"Big whorls have little whorls
That feed on their velocity;
And little whorls have lesser whorls;
And so on to viscosity."

Lewis Fry Richardson

Turbulence is a multiscale phenomenon where small eddies in turbulence have very short timescales. This alone tends to make them statistically independent from the mean flow. Therefore, smallscale motion depends only on the rate at which it is supplied energy from the larger scales, and the rate at which kinetic energy is dissipated into heat. The two rates of change are assumed the same so that the net rate of change is small comparing to the rate of dissipation.

This is the basis for Kolmogorov's universal equilibrium theory. It basically says that the rate of energy supply to smallscale eddies is equal to the the dissipation rate:

$$U^3/L \sim \epsilon \, .$$

In other words, the dissipative effects of viscosity can be estimated from the large scale dynamics, which are effectively inviscid. Inertial effects cause a transfer of energy from small to large wavenumber space by vortex stretching.The mean flow kinetic energy transforms into turbulent energy in the form of large eddies which cascade down to smaller eddies and so on, the remaining fluctuations are ultimately dissipated by viscous damping.

Turbulent velocity fluctuations generate large momentum fluxes between different regions of the flow which is a process analogous to stress (Reynolds stresses). The Reynolds stress is what quantifies the contribution of the turbulent motion to the mean flow. Because the momentum transfer mechanism resembles molecular diffusion, turbulent moment exchange is modeled with an eddy viscosity.

All this discussion is still inside the boundary layer itself. Outside the boundary layer is the mean wind which supplies the necessary shear for turbulence inside the boundary layer. Although this wind is not affected by the turbulent fluctuations within the boundary layer, it is the reason why they exist.


T-phigram satellite derived sounding vs model output question I have this satellite derived sounding(T-phi gram) of a mountainous area and from what little I can make out it appears that probability of precipitation is almost negligible. Let us assume my model output for the same time predicted the rainfall event accurately that happened at the given time and TRMM satellite data was able to pick up the rainfall event as well. Is there something in the sounding diagram that I have displayed that can pick up the rainfall event as being  likely? I for one cannot make it out as  CAPE is zero and CIN is greater than 200. I obviously have a follow up question  - accuracy of satellite derived soundings in mountainous areas but that is for later.

As already commented; a good indicator for rain in soundings is that the lower troposphere is saturated by water. Individual saturated levels would imply moisture, but if the moisture doesn't reach the surface then it maybe just clouds or rain that evaporates before reaching surface (virga). The deeper the saturated layer, the better indicator for rain it is. The dew point and ambient temperature doesn't necessarily have to be exactly the same, but very close to each others.

You pointed out cin and cape, but they are really just indicators for forcing convection and aren't necessarily present when it already rains.


Why are impact craters radially symmetric? Okay, so I believe that most of the impact/collisions happen at oblique angles to the planet's radial direction. (I am not very sure about this, but since it is not a freefall, we can assume that the collision is oblique).

So why are most of the craters radially symmetric?

Why isn't the depression skewed?

I have almost never come across a photograph of a skewed crater.

The main reason why impact craters are close to symmetrically round is because it's the explosion of the impactor, not its collision, that creates the impact crater. The impactor is travelling so fast that, rather than simply exploding on impact, it burrows deep into the collision site, heats up from compression and friction, and explodes deep underground, thus creating a more-or-less perfectly round crater.


Cooling effect by evaporation Why exactly does water cool down by evaporation? What happens in this process?

How much does it cool down? What's the formula to describe this process?

Someone (Casey?) can probably provide a fuller answer, but the basic idea is that ice molecules are kind of locked into place by the molecular structure of the ice crystal, and can't vibrate very much. Increase the energy, and the molecules vibrate more until the molecular attraction is disrupted to become water, when they vibrate a lot. Increase the energy still further and the individual molecules are flying about like crazy, thereby turning into a gas. Water is an extraordinary compound. The energy required to break the attraction between molecules in the liquid state is a whopping 2258 kilo-joules per kilogram - a handy property that brought about the age of steam, and the industrial revolution.

It is this phase transition energy (latent heat) that produces the cooling. The principle of conservation of energy, as applied in nature, requires that to balance the energy gain by the water vapour, there has to be an equivalent energy loss somewhere - hence the cooling effect on the liquid.


Why are these patterns of scattered sunlight aligned to the local horizontal and vertical directions? The information discussed in the CleanTechnica article Full Fledged 5 Alarm Climate Emergency In Antarctica is certainly disconcerting, but the stock photo of the sky and various atmospheric phenomena of sunlight scattered in the atmosphere is still beautiful. My question is about this photo.

I see two circles around the sun, meaning light is scattered at certain angles ABC where B is the scatterer, A is the Sun, and C is the observer. However there are several features that are oriented with respect to the the local horizontal and vertical as well. For example, a long line extending to the left and right from the Sun parallel to the horizon with bright spots where it intersects the inner ring, and the beginnings of arcs, tangent to the tops of the circles but curving vertically upward.

Question: Why are these patterns of scattered sunlight aligned to the local horizontal and vertical directions?

Note: All of the links in this answer point to various parts of Les Cowley's excellent Atmospheric Optics site. Les combines photographs, simulated images, and descriptions of the underlying physics to beautifully portray and explain a number of different optical effects in our atmosphere.

Note: The imagery on that site is copyrighted. Please do not edit this answer to portray images from that site.

That's a very nice picture that shows a number of ice halos. Ice crystal halos are caused by various shapes of ice crystals. Some of these halos such as the small circle that encircles the Sun in the image in the question are easily seen at all latitudes. Others only appear in very high latitudes, and even there they are rather infrequent.

The small circle is the 22° halo. This is a frequently seen halo, much more common than rainbows. It's caused by poorly aligned hexagonal prism ice crystals. If you look closely, you'll see that the sky is darker inside the 22° halo. This is similar to how the sky is darker outside the primary bow of a rainbow. Unlike a rainbow, the color separation is very small, making the 22° halo white rather than colored. If you look closely, you can see that the inner edge has a bit of a reddish tinge.

The two bright spots on the sides of the 22° halo are sun dogs. These result from hexagonal plates of ice with their large faces nearly horizontal. The curve the intersects the Sun, runs parallel to the horizon, and intersects the 22° halo at the sun dogs is the parhelic circle. Parhelic circles result from sunlight reflecting off nearly vertical faces of ice crystals. The mustache atop the 22° halo is the upper tangent arc. Tangent arcs result from ice crystals that form hexagonal columns rather than hexagonal plates. As is the case with the 22° halo, sun dogs, parhelic circles, and tangent arcs are fairly common.

The partial circle outside the 22° halo is the not so common supralateral arc, or possibly the even rarer 46° halo. Atop that is the circumzenithal arc.


Can weather radar be used to track swarms other than mayflies? Along the Mississippi River swarms of emerging mayflies have been seen on radar.  The radar and image below are from a July 11, 2017 emergence near LaCrosse, Wisconsin.  On the radar you can see the mayflies emerge from the river and head toward the north.

This image was taken in LaCrosse during the emergence.

Radar & Image Source: National Weather Service

Is it possible that other swarms have or can be tracked by weather radar?

Bird migration has been studied by Weather radar Bird migration study using weather radars  and the monitoring can be visualized here - Bird migration density profiles. A github site Time Integrated Multi altitude Migration Patterns  has been developing algorithms to estimate the density, speed and direction of migration movement at different altitudes around a radar.


Do normal modes of oscillation cause permanent deformation? It is known that when a large earthquake occurs, say $M \ge 9.0$, The surface waves travel around Earth over and over, "ringing the surface like a bell". The GIF below is an example (Image Source):

Do these normal modes cause permanent deformation AWAY from the earthquake source or does Earth affected simply slide back in place after the wave passes through it? If there is no permeant deformation, why does the surface near (but off source) crack and fault?

These are visco-elastic oscillations that cause virtually no permanent deformation.

Following the Tohoku 2011 earthquake, this gravimeter in Metsähovi, Finland, measured a radial oscillation mode amplitude of 0.06 mm. The Earth's radius is 6371 km. So the resulting strains would be extremely small.

All but the lowest radial mode decays after a few days because the energy of the oscillations gets converted to heat by dissipative processes.


What causes these odd-looking currents in the Tasman Sea? I was looking at the model ocean current maps from earth :: a global map of wind, weather, and ocean conditions for 2015-10-07 00:00 UTC and there are a lot of odd-looking 'whirlpool' areas off the eastern coast of Australia. Anyone know the explanation? Is this a common occurrence? Is it related to the strong El Niño?

Great question. These features are mesoscale Eddies and they are akin to hurricanes in the atmosphere. They are the ocean’s high or low pressure systems and are the result of instabilities. The cyclonic eddy (counterclockwise direction in the northern hemisphere) is called a cold-core eddy and the anti-cyclonic eddy is called a warm-core eddy.

Unlike destructive hurricanes, ocean eddies are important physical processes for the transport of heat and particulate matter. They stir up the ocean drawing up nutrients from the lower depths and fertilizing waters as they propagate. They are important for the transport of marine organisms in the offshore direction and support phytoplankton and zooplankton production.

In the Tasman sea, this region is known as 'Eddy Avenue' which speaks to their ubiquity and persistence. In Everett (2012) they identified 30 thousand eddies in a period of $15$ years.

  ... at a density of 61 cyclonic and 63 anticyclonic eddies per $10,000$
  km$^2$. On any given day there are 16.8 cyclonic and 17.8 anticyclonic
  eddies within the Tasman Sea. Tasman Sea eddies are typically smaller
  than the global average ($82$ km radii compared with $86$ km), have a
  faster rotational speed ($23$ cm s$^{-1}$ compared with $15–16$ cm
  s$^{-1}$) and have a larger Sea Level Anomaly($10$ cm compared with
  $6–7$ cm) (Table 1).

Generation:

  “When the current separates from the coast, it gets complicated. It
  starts to wobble; it meanders. Rather than going in a relatively
  straight path like the Gulf Stream in the North Atlantic, it walks
  like a drunk man.” Not only does the EAC wobble, it U-turns. [...] The EAC is a bit  anomalous.” About two-thirds of the current retroflects back up into
  the eastern Pacific, breaking up the EAC further. “It really is a
  current of eddies.” Such instabilities saturate Eddy Avenue with
  eddies.

As far as the El-Niño connection, I can only speculate. But generally, El-Niño will give rise to positive SST anomalies. The figure below shows recent positive SST anomalies which are relatively strong near the coast. Because ocean temperatures are higher ocean eddies can increase in size and strength.

References

Everett, J. D., M. E. Baird, P. R. Oke, and I. M. Suthers. 2012. An avenue of eddies: Quantifying the biophysical properties of mesoscale eddies in the Tasman Sea. Geophysical Research Letters 39, L16608, doi:10.1029/2012GL053091.


What would be a reasonable set of thresholds for flood severity classes? When working with extreme hydro-meteorological events, flood in particular, it is common procedure to classify each event by its return period/recurrence interval. This probabilistic measure has the quality to provide a standard and homogeneous measure of the different events that eventually happened in diverse geographical areas, given their relative frequency. So, a 100-year flood is a potentially devastating event both for a flood prone area, and for an area where flood events are extremely rare.

My problem is now how to set a reasonable threshold to group events characterized by a "similar" return period. For instance, let's assume I want to set three classes: mild, middle, and severe flood events, what would be a reasonable return period cut? Is there any similar procedure for structural engineering/water infrastructure design? It would be lovely if you could also provide some references justifying your choice.

One existing classification for return period events is minor and major flows, which basically classifies floods into those that the storm network (pipes and small conveyance network) is designed to handle, typically in the 2-10 year event range, and those more major floods which will overwhelm the stormwater infrastructure and are mainly conveyed by overland topography and larger flow channels/watercourses (>10 year event). The definition of major and minor return periods depends on the level of design in your are of study, but that is one classification. This distinction in major/minor flows is common and you can find lots of resources, one example is in the Ontario Drainage Manual.

Given that you want a small/medium/large classification, I would put minor flows (say 5 year and smaller, based on the study area) into the small category, everything above a minor flow to the 100 year event into the medium category, and everything 100 year or larger (i.e. 100 year and regulatory event) into the large flood category. The 100 year as you mentioned is a very common standard for a large flood event. The Regulatory event is typically the largest observed flood on record or similar estimate for a larger than 100 year flood event.

Hope that helps!


What is the motivation of using the Enhanced Fujita Scale in place of the Fujita Scale? In 2007, the US started using an Enhanced Fujita Scale in place of the Fujita Scale. From a "civilian's" perspective, the Fujita Scale seemed to measure wind whereas the Enhanced Fujita Scale measures damage. This would suggest that tornadoes based on the EF scale is retroactively labeled rather than labeled while the tornado is taking place. Also, going from saying "F5" to "EF5" is a change.

What is the motivation of using the Enhanced Fujita Scale in place of the Fujita Scale? What are the main differences of the two scales that allowed the Enhanced Fujita Scale to be used today in the US?

Both the Fujita (F) and Enhanced Fujita (EF) scales measure damage and then use damage as a proxy for wind speed.  Wind speed at the low levels is not directly measured unless the tornado is either very close to a doppler radar site or there happens to be a mobile radar sampling it.  This provides very few tornadoes with directly sampled wind speed and is the exception rather than the rule.

Where the F and EF scales differ primarly is that in the EF scale construction methods may be considered, not just the damage observed.

Damage is used as a proxy for windspeed by examining damage, construction techniques and methods (EF scale only), materials, and other factors and then determining what threshold wind speed could cause that damage.  This means that identical damage can result in different windspeed estimates.

For example, a house that is completely destroyed and leaves behind a clean concrete slab is generally considered EF-5 damage, but some houses with poor construction have been found to not be physically tied to the foundation.  A particular case in northern GA, USA had tornado winds blow down a garage door and then lift the house directly off the slab and take it away.  This also leaves a clean concrete slab, but the construction methods will cause a lower wind estimate and a weaker tornado determination because less wind was required to cause the damage.

The only other difference between the F and EF scales are that some of the wind speed estimates have been lowered in the EF scale and more descriptive damage indicators are used for wind speed estimates to help standardize those estimates.

In summary, the EF scale differs from the F scale:

EF scale can consider construction methods
EF scale has more descriptive damage indicators used to estimate wind speed
EF scale has reduced wind speeds in each category to better align with engineering estimates of damage


What makes the conditions at the core/mantle boundary ideal for aluminum to combine with other elements besides oxygen? Recently, steinhardite was accepted as a new mineral by the International Mineralogical Association.  It's quite an interesting story in its own right. There's an interesting article in New Scientist about it, but it's paywalled.

The formula for steinhardite is $\ce{Al63Cu24Fe13}$.  It's an ultra-rare quasicrystal, at least partially because of the mixture of aluminum without oxygen, as I understand it.

One of the critics (as quoted in the article)

  ... who promptly declared the possibility
  of the sample being natural as ‘‘impossible’’. His
  concern was not the degree of perfection but,
  rather, the baffling presence of metallic Al in
  cupalite, khatyrkite and in the icosahedral
  quasicrystal phase. Metallic Al has a remarkably
  strong affinity for O, such that it could not
  possibly form naturally on the surface of the
  Earth, he argued ... he amended the conclusion to allow for the
  improbable possibility that it could have formed
  under the intense heat and pressure that exist near
  the core mantle boundary or in a high impact
  collision of meteors in space. [1]

The core/mantle boundary is obviously rife with lots of chemical interactions, but what is it exactly about the conditions that prevents aluminum from oxidizing?  Is it just physical pressure or the presence of other gases?

There's the obvious fact that the aluminum isn't exposed to the atmosphere, but my (limited) understanding is that oxygen is plentiful in combination with other elements like silicon.

  Reference:

  Bindi, L. & Steinhardt, P.J. (2014) The quest for forbidden crystals. Mineralogical Magazine, 78(2), 467–482. [DOI] [PDF] (seems to be freely available)

A reason found experimentally is that the pressure and temperature conditions at the mantle-core boundary result in the reduction of aluminium oxides.  According to the Nature article Chemical interaction of $\ce{Fe}$ and $\ce{Al2O3}$ as a source of heterogeneity at the Earth's core–mantle boundary (Dubrovinsky et al. 2001) through their experiments simulating the thermochemical conditions at the boundary, that one of the main factors in the core-mantle boundary region is

  that iron is able to reduce aluminium out of oxides at core–mantle boundary conditions, which could provide an additional source of light elements in the Earth's core and produce significant heterogeneity at the core–mantle boundary.

Further, from the ESRF Highlights 2001 webpage Chemical Interaction of Iron and Corundum at High Pressure and Temperature: Implication for the Earth's Deep Interior, experimentally found that the following reaction, forming iron-aluminium compounds (amongst other alloys) occurred at temperatures that are believed to exist at the mantle-core boundary:

$$\ce{($2+3x$)Fe + $x$Al2O3 -> 2FeAl_{$x$} + $3x$FeO}$$

Where $x$ varied between 0.02-0.03 to 0.25


What is the relationship between the derivatives of specific volume and potential temperature with height? While studying about atmospheric waves, I found a passage in my book in which a equation involved the term  $$ \frac{1}{\alpha }\frac{\partial \alpha }{\partial z}$$
where $\alpha$ is the specific volume of air , which was replaced by $$ \frac{1}{\theta }\frac{\partial \theta }{\partial z}$$, where $\theta$ is the potential temperature, but with no details on how this was done. I tried to find a relationship between specific volume and potential temperature that would give me this equivalence, but with no success. How can I prove this?

$$\theta=T\left(\frac{P_0}{P}\right)^\frac{R_d}{c_p} \tag{1}$$
$$\alpha=R_d T P^{-1} \tag{2}$$
$$\frac{\partial P}{\partial z}=-\rho g \tag{3}$$

It can be shown that $$\frac{\partial \theta}{\partial z}=\frac{\theta}{T}(\frac{\partial T}{\partial z}+\frac{g}{c_p }) \tag{4}$$

Therefore $$\frac{1}{\theta}\frac{\partial \theta}{\partial z}=\frac{1}{T}(\frac{\partial T}{\partial z}+\frac{g}{c_p })\tag{5}$$

So if we take $\frac{\partial \alpha}{\partial z}$, we find $$\frac{\partial \alpha}{\partial z}=R_dP^{-1}\frac{\partial T}{\partial z}-R_dTP^{-2}\frac{\partial P}{\partial z}\tag{6}$$

Then we can rewrite (6) using (2):

$$\frac{\partial \alpha}{\partial z}=\frac{\alpha}{T}\frac{\partial T}{\partial z}-\alpha P^{-1}\frac{\partial P}{\partial z}\tag{7}$$

Divide by $\alpha$ $$\frac{1}{\alpha}\frac{\partial \alpha}{\partial z}=\frac{1}{T}\frac{\partial T}{\partial z}- P^{-1}\frac{\partial P}{\partial z}\tag{8}$$

Employing (3) $$\frac{1}{\alpha}\frac{\partial \alpha}{\partial z}=\frac{1}{T}\frac{\partial T}{\partial z}+ P^{-1}\rho g\tag{9}$$

Which is the equivalent of

Employing (3) $$\frac{1}{\alpha}\frac{\partial \alpha}{\partial z}=\frac{1}{T}\frac{\partial T}{\partial z}+ P^{-1}\alpha^{-1} g\tag{10}$$

Now, it may get a little sketchy in this derivation. But we're close. Assuming an adiabatic transformation ($dH=c_p dT-Pd\alpha=0$ and $H-H_0=c_pT-P\alpha$), we can rewrite (10) to look a little funky

$$\frac{1}{\alpha}\frac{\partial \alpha}{\partial z}=\frac{1}{T}\frac{\partial T}{\partial z}+ \frac{g}{H-H_0-P\alpha}\tag{11}$$

Since enthalpy is conserved, $H=H_0$

$$\frac{1}{\alpha}\frac{\partial \alpha}{\partial z}=\frac{1}{T}\frac{\partial T}{\partial z}+ \frac{g}{c_p T}\tag{12}$$

And finally,

$$\therefore \frac{1}{\alpha}\frac{\partial \alpha}{\partial z}=\frac{1}{T}\left(\frac{\partial \alpha}{\partial z}=\frac{1}{T}\frac{\partial T}{\partial z}+ \frac{g}{c_p}\right)=\frac{1}{\theta}\frac{\partial \theta}{\partial z}$$


How far from basalt bedrock can magnetometic survey find archaeological features? Magnetometry is used to find archaeological features such as stone walls or ancient hearth. But it usually cannot be used for archaeological prospection in areas where the bedrock is strongly magnetic. Let's assume basalt - it is quite common near the town I come from. With an average cesium vapour magnetometer, how thick must be the soil so that I could find remains of highly magnetic features like remains of a burnt wattle-and-daub house or an iron depot? And if operating near a fault between magnetic and non-magnetic rock, how far from the magnetic rock can I find weakly magnetic situations like disturbed soil?

EDIT: I expect approximate answer. An answer I would expect could start: "Iron is more magnetic than basalt, so several kilograms of iron (or iron rust) could be found even less than a meter above the bedrock under condidtions X, several meters otherwise. Very small iron items and piles of burnt soil would usually need several tens of meters..." I just guess all the facts, I don't know, I'm just an archaeologist with no background i geophysics. The aim of this edit is to emphasize that I don't need exact numbers, but I need an idea which numbers might be exact and which are likely to be completely wrong.

You can get a good idea of the magnitude and wavelengths of typical archaeological magnetic anomalies with a literature search. For instance this page shows a magnetic map of fire hearths http://en.wikipedia.org/wiki/Magnetic_survey_(archaeology)

Geology is a lot more complicated though and there are many variables that might affect the background magnetic signature. It doesn't matter how much you study up on basalt rock properties you still won't know enough about the rocks in your project area to predict the outcome of a survey.

Your best hope is to use prior experience from other surveys close to your project area. If a survey worked in one farmer's field then it will probably work in the adjacent field as well.

If no one has collected any magnetic data close to your project area then go ask the geophysicists if they will do a test line or two. If it works great, if not then try something else like magnetic gradiometry, resistivity or ground probing radar.

Sorry I can't give you a definitive answer to your question. I understand what you are asking but geology is just too complex to give you a useful rule of thumb.


Where are the oldest igneous rocks found? I'm trying to catch up on my homework for earth science, but I'm having a difficult time searching for an answer to my question.

Zircons from Australia at 4.4Ga, and perhaps basalts from a Canadian island at 4.5Ga.

It would interest you to know the quest of Boston University geochemist Matthew Jackson, who is searching for the oldest basalt and mantle rock that exists.

His work isn't entirely agreed upon, as they are using all kinds of difficult isotopes which are a subject of controversy. Probably the most current information on early basalts are the claims and counter claims relating to Matthew Jackson in published articles, which have a lot of chemistry in them.

http://news.nationalgeographic.com/news/2010/08/100812-worlds-oldest-rocks-magma-earth-nature-science/

https://www.bu.edu/today/2012/little-rock-at-center-of-big-controversy/

https://scholar.google.fr/scholar?hl=en&as_sdt=0%2C5&q=tungsten+basalt++oldest&btnG=

"We've been looking for pieces of the mantle that might have survived the chaotic mixing and churning within the deep Earth," said Boston University geochemist Matthew Jackson.

"We found rocks that reached the surface some 62 million years ago—suggest a whole reservoir of the primordial rock could still lie somewhere beneath the Arctic"

There are moon basalts from 3.7 Ga years ago, they are a bit mysterious, and lunar plagioclase feldspar at 4.5, appear to have formed when feldspar crystallized and floated to the top of a global magma ocean that surrounded the Moon soon after it formed.


Near-Surface Investigations: FWI vs. MASW MASW is a common processing method for civil/geotechnical and even for oil/gas exploration (usually weathering static corrections) applications. In my experience, it seems to work well for most environments and various subsurface conditions.

The more I learn about FWI and MASW (for either Raleigh- or Love-waves), the more I realize that perhaps one day FWI methods will surpass any MASW processing because it attempts to overcome the limitations naturally imposed by MASW because of its inherent assumptions of subsurface conditions.

To date, I cannot find a case study that compares both methods in a single environment. Also, I realize that deriving a reliable source function, recording the 3-D seismic wavefield, and overcoming the stability constraints associated with multiparameterization of FWI (especially for elastic wave phenomenon) is task to be handled with in the future.

My questions are: (1) Has anyone seen a paper dealing with comparing both methods - if so, where? (2) Will some form of FWI possibly surpass MASW workflows (e.g. ParkSeis or SurfSeis) in the near future?

I think there are some initial exploratory abstracts out there on the topic, e.g., http://www.earthdoc.org/publication/publicationdetails/?publication=75396 . But not much yet.

My view is that that MASW (multichannel analysis of surface waves) is simply so much more robust in practice compared to FWI (full waveform inversion, which really doesn't work as spectacularly well as some papers may suggest; the method requires a LOT of iterative and hands-on work, and is furthermore extremely computationally demanding, without always giving dramatically better results compared to travel-time tomographies...)... hence, I think that MASW will remain the standard in the coming future, until FWI truly becomes a 'cheap' and 'hands-off' method, which could easily take another 15+ years, I imagine...


How did Australia separate from India? So on a lot of maps of tectonic plates, it appears that India and Australia share a tectonic plate (hence the Indo-Australian plate). But in maps of Pangaea, India and Australia appear to have once shared a border. Since continents only move because the plates they sit on move, how is it that India and Australia have changed relative positions if they share a plate?

I've looked around a lot online and I can't seem to find a specific reason, and my science teachers weren't much help either. Supposedly they once sat on separate plates, and diverged from each other, with a mid ocean ridge spewing out sea floor between them. If this is the case, how did they fuse together? Also, I believe that Australia is currently moving towards India as well. Do convection currents change direction?

They don't really share a plate, now they did for a long time and the boundary between them is rather recent but they are separate plates.

BUT this was only discovered recently, recently as in 2012, so older references treat them as the same plate.  The "indo" in indo-australian plate is being dropped from more modern references.

The two plates are moving in almost the exact same direction and speed, so it is easy to see why it took so long to be discovered. Almost is also the key, the forces separating them up is rather weak, tectonically speaking, without a lot of heavy volcanics so the separation is very slow. Now they were not tightly connected to begin with, so there is no continental fault between them. Spreading centers


Which are the biggest methodological differences between the archaeological and geological approaches to stratigraphy? Stratigraphy, or study of rock or soil layers (strata), was originally introduced as a branch of geology. However, it is often applied in other disciplines, especially in archaeology and paleonthology. As an archaeologist (though not a field archaeologist), all I learnt about stratigraphy was taught from archaeological perspective. So I'm curious how the approach of other disciplines to stratigraphy differs from the archaeological. I'm especially interrested in geology - because it is the main and original discipline for stratigraphy, and because the geological time is very different from the archaeological time.

I know the basic principles such as law of superposition and principle of original horizontality are common. On the other hand, the time (hundreds or thousands of years x millions of years before present), materials on which stratigraphy is studied (sediments often created by human culture x rocks) and dating methods differ.

But how do these differences affect the "theoretical" methodology? That it is usually not possible to dig 100 million old strata with a spade is natural, but how about interpretation?

Is geological stratigraphy visualized with Harris matrix or something very similar too? Are there any special principles that usually apply only on very old strata? Or is geological stratigraphy simpler, so some archaeological stratigraphy rules don't apply? Is there any distinctions between various stratigraphic units (layers and cuts, or other distinctions)? If yes, which categories are usually distinguished?

As I see it there are no clear differences. There are, however, processes that are not compatible with a superposition principle. In geology, it is possible for layers to be folded and result in inverse age relationships. Packs of sediments can also be pushed over other layers during, for example mountain building, so that sequences are out of order or even repeated, almost like shuffling a deck of cards. It is also possible for, for example, magma to penetrate into rocks and generate much younger layers within an older rock mass. A depth, mass is added to the crust by melting and solidification while cooling such that rock units of different age can be found parallel (in a stratigraphic context) to each other. Hence the superposition principle only applies in sedimentary rocks and unconsolidated sediments that has not undergone and significant tectonic activity. But, I can also imagine that archaeological material can (although not extensively) be subject to disruptions in certain environments where active tectonics are at play or for example where glaciers act to push material forward and generate repeat sequences.

To expand on the second part of the post. Geological stratigraphy is established from physical exposures and by measuring structural shapes such as the strike and dip of strata (a branch of geology called Structural geology. Very little is gained from created exposures such as open day mines, mine shafts of other dug pits. It is also possible (as in archaeology) to use geophysical methods to infer layer by ground penetrating radar, seismics etc. It should be mentioned here that methods and possibilities vary between bedrock and unconsolidated sediments, where I would venture to say that archaeology and studies of the unconsolidated sediments are very similar using test pits and coring with the addition of understanding transport mechanisms to understand how and why certain sediment layers exist where they are.

Visualisation pof geological data is usually done in sections or logs of boireholes with attempts to connect between observed sections. In bedrock where there is not only vertical variability but also significant horizontal, such as in igneous rocks, obtaining a precise image is very difficult


What is the status of the Raymo & Ruddiman idea that Tibet cooled the Earth? What is the current status of the Raymo & Ruddiman hypothesis that the uplift of the Tibetan Plateau during the Cenozoic cooled the Earth, resulting the current ice age(*)?

cf. Raymo, M.E. and W.F. Ruddiman (1992) Tectonic forcing of late Cenozoic climate. Nature, v. 359, p. 117-122.

This argued that enhanced erosion rates from the uplift of the Tibetan Plateau took CO2 from the atmosphere and cooled the Earth enough for polar ice caps to form. This was popular in my undergraduate days, although there were questions about the precise timing of events, and stopping a "runaway cooling" event.

(*) Ice age in a geological sense, i.e. with ice caps at one or both of the poles.

The Tibetan Plateau uplift is still generally considered as playing a role in the Neogene cooling through the process you explained in your question (see for instance the seminal Zachos et al. 2001 and more recently Garzione 2008).
It is probable that other phenomena played a role as well such as the diversification of diatoms (which are, today, the most efficient biological carbon sink, e. g. Goldman 1993; Ragueneau et al 2000) around 15 Ma (Lazarus et al 2014 [Disclaimer: I am a co-author of the latter paper] ) or changes in the ocean circulation (specifically an increase in the proportion of bottom water originating from the Southern Ocean; Flower & Kennett 1994).
That being said, the cooling in question here would be the one starting at ca. 15 Ma. However the Cenozoic cooling trend started way earlier, in the Early Eocene (after the Early Eocene Climatic Optimum, aka EECO), with ice on the eastern Antarctic
continent as early as the Late Eocene / Early Oligocene (see again Zachos et al 2001).

Sources:

Flower, B. P. & Kennett, J. P., 1994. The middle Miocene climatic transition: East Antarctic ice sheet development, deep ocean circulation and global carbon cycling. Palaeogeography, Palaeoclimatology, Palaeoecology, 108: 537-555.

Garzione, C. N., 2008. Surface uplift of Tibet and Cenozoic global cooling. Geology, 36: 1003-1004.

Goldman, J. C., 1993. Potential role of large oceanic diatoms in new primary production. Deep-Sea Research I, 40(1): 159-168.

Lazarus, D., Barron, J., Renaudie, J., Diver, P., & Türke, A., 2014. Cenozoic Planktonic Marine Diatom Diversity and Correlation to Climate Change. Plos One, 9(1): e84857.

Ragueneau, O., Tréguer, P., Leynaert, A., Anderson, R. F., Brzezinski, M. A., DeMaster, D. J., Dugdale, R. C., Dymond, J., Fischer, G., François, R., Heinze, C., Maier-Reimer, E., Martin-Jézéquel, E., Nelson, D. M., Quéguiner, B., 2000. A review of Si cycle in the modern ocean: recent progress and missing gaps in the application of biogenic opal as a paleoproductivity proxy. Global and Planetary Change, 26: 317-365.

Zachos, J., Pagani, M., Sloan, L., Thomas, E., Billups, K., 2001. Trends, rhythms, and aberrations in global climate 65 Ma to Present. Science, 292:686-693.


How much garbage goes into the Pacific Ocean every year? In this article, they mention that:

  More than 4.8 million metric tons [of] plastic waste gets dumped into the world’s oceans from land each year. And this number is just a conservative estimate. Researchers believe the real amount could be as high as 12.7 million metric tons.

How much total garbage is going into the Pacific Ocean every year? and what fraction of the garbage is "biodegradable".

In this other article, they point out that the size of the Great Pacific Garbage Patch is much larger than previously thought.  They go on to say that they are developing a technology that will clean up some of the garbage:

  The organization hopes to deploy its Pacific array in 2020 and says it could remove almost half of the Great Pacific Garbage Patch ― more than 150 million pounds of trash ― in a decade.

This is great news if it actually works out.  However, how much garbage will still be retained at the sea floor (or suspended below the level at which the garbage can be removed)?

I've been looking for information on non-plastic garbage, and haven't had much luck. Plastic waste is an extensively researched topic. I don't have access to  Jambeck et al., Science 2015, but I did find a graphic and summary. The numbers are all year-long totals for 2010.

The study's estimated range of plastic entering the ocean is 4.8 million to 12.7 million metric tons (MMT).

For the United States we can find some other figures to try to complete the picture. According to the EPA, in 2012, the US generated 251 MMT of municipal solid waste (MSW). Of that, 11.7% was burned, 34.5% was recovered by some sort of recycling, and 53.8% was discarded (Fig. 4). Plastics compose 12.7% of pre-recycling waste but 17.6% of post-recycling waste. Biodegradables (here I'm using food, paper, yard trimmings, and wood, but not textiles) consist of 61.7% of trash before recycling and 52.8% after.

So if we assume those ratios can be applied to the plastics sent to the ocean (8 MMT) you get the following:

Assuming global ocean waste has a similar composition as US
non-recycled waste, there are 63 MMT garbage entering the sea, of
which 39 MMT are biodegradable.
Assuming global ocean waste has a similar composition as US recycled
waste, there are 45 MMT garbage entering the sea of which 24 MMT are
biodegradable.


A guide to how climate change will affect different countries Let's assume that the climate change won't be prevented. I'm looking for a guide to show how the climate change will affect different countries.

Specifically, I'm interested in comparing following countries:

Switzerland
Panama
Chile
Uruguay
Malaysia
Ukraine

I'm looking for a guide which would combine as many known factors as possible, like sea level rise, ocean acidification, impact of climate change on agriculture (Ukraine) or growing forests (Panama), fisheries (Chile) etc etc.

There is some basic information here, but I feel that this index is too basic, and doesn't give any idea about concrete dangers faced by each country in the list

Can anyone recommend to me a source which can be used to imagine the future as vividly as possible for each country in question? I am interested in the estimates for the next 300 years

There's a fair bit of unknowns for what you're asking, 300 years and specifics.   For one, climate change modeling is based off CO2 levels and CO2 levels long term are difficult to predict.   That's why they run hundreds of models, each with different circumstances.  Nobody can make an accurate assessment of mankind's CO2 output will be 50 or 100 years so the further out you go the greater the unknowns.  Targets are being set for 2050, but whether they will be reached is a big unknown and I've never seen anything that goes for 300 years.  Most of the models run till 2100.

Some Unknowns:

Will CO2 PPM peak at 500 or 600 or higher?   Will it fall below 400
in 100 years?
Will the oceans continue to absorb CO2 or will they warm to the point
where they stop.
Will the North Atlantic current stop or weaken?   That would have an
enormous effect on European climate.
Will large chunks of ice break off or will the ice sheets remain
mostly intact?

These are impossible things to predict with any accuracy and they significantly effect the outcomes you've asked for.

Smaller effects, such as whether the Sun will enter an extended solar minimum or whether we have a big volcanic eruption like the one in 1815 (which would slow things down for 5-10 years, but wouldn't have a significant long term effect).   Other questions are whether parts of the Earth can be greened, artificially, which might not measurably slow down the warming but it could ease the effects of drought in some areas.

Bottom line is that "basic" predictions might be just as good as detailed because of all the unknowns.   A few aspects are pretty straight forward, like knowing the effect of 1 foot of sea level rise, but predicting how fast the oceans will rise 1 foot is very difficult.   The effects of ocean acidity and some weather driven species migration is somewhat predictable too.   Predicting where droughts are more likely to happen can be done as well, but as I said above, might be preventable with strong irrigation efforts.

Rough predictions aren't hard to find, but for the 21st century only.  Anything further out than that is probably lots of guesswork and not carefully modeled.    Basic and this century is probably as good as this field of study gets.

Articles here and here.  I imagine those are both based on the 5th assessment report.

footnote:  If you read assessment reports online, keep in mind the labeling system - 5th; AR5,  4th; AR4, 3rd; TAR, 2nd; SAR, first; FAR.  Given how fast this field tends to update, I'd mostly just read IPCC reports labeled AR5, perhaps AR4.   Anything before then is quite dated by now.