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uniquorn

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Re: "Stupid" Questions :o
« Reply #2700 on: October 22, 2019, 11:10:42 PM »
the increased density of surface waters as they cool and sink create enough convection to stir up the top tens of meters of ocean, getting all that heat to the surface.
Are you sure about that? itp103 microcats at 5m and 6m in the Beaufort recently, temperatures only occasionally peaking at the entrance to the amundsen gulf.

slow wing

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Re: "Stupid" Questions :o
« Reply #2701 on: October 23, 2019, 06:24:33 AM »
Thanks for all your interesting & some authoritative responses in this discussion.




I still don't understand, how can you use a very thin slice of a full model to approximate the true situation?

I can do it because a) I am only seeking order-of-magnitude accuracy & b) am considering the limited & somewhat artificial situation where the only heat transport mechanism is thermal conduction.



I think I found a better approximation in this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6114986/

This is comparing apples to oranges. You're showing an amount of heat whereas I calculated a rate of heat transfer. That's a lot of heat but it still has to get to the surface to affect the ice.




Have you all forgot the basics of sea ice formation? RoxTheGeologids, macid, slow wing?

Yes, I'm worried that some of the people here may have forgotten more about that than you or I ever knew.




I hope that the current expedition will show how this happens in real time! It's a really interesting theory.. lets see if the real world works that way.

Yes, an exciting prospect!
« Last Edit: October 23, 2019, 06:52:39 AM by slow wing »

binntho

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Re: "Stupid" Questions :o
« Reply #2702 on: October 24, 2019, 08:01:50 AM »
the increased density of surface waters as they cool and sink create enough convection to stir up the top tens of meters of ocean, getting all that heat to the surface.
Are you sure about that? itp103 microcats at 5m and 6m in the Beaufort recently, temperatures only occasionally peaking at the entrance to the amundsen gulf.

No, I'm not at all sure that it will stir up the top tens of meters. When I wrote that a couple of days ago, I had just been reading on Wikipedia that the top 100-150 meters were involved, and didn't really believe that it could be that much (or, as is more likely, that I had totally misunderstood what they were saying). So I tempered it down to "tens of meters".

But the point perhaps is that the accumulated SSTs in these seas is significant, and given that heat absorbtion is by far greatest in the top layers, perhaps the heat doesn't go all that deep. And when atmospheric temperatures start to go down below the SST then the process of cooling and sinking kicks in, resulting in a fairly efficient heat transfer to the surface.

Perhaps the best evidence for the efficiency of this heat transfer is the (admittedly anectdotal, but seemingly robust) tendency for the ocean surface not to start freezing until the air temps hit around -11C.

Since the freezing point of the surface is -1.8C, the -11C doesn't make sense unless you see it as breaching the cooling-induced turbulence, and managing to actually freeze the top layer before it sinks. Which again tells you that this turulence is strong enough to keep the ocean ice free in the current temps of between -2 and -3 in most of the still non-frozen parts of the Beaufort, Chukchi, Laptev and EES.

Of course there is a balance ongoing here. The winds off the centra Siberian coast, and off the ice  itself, are around or below -10C, but the warm up very quickly as they flow in over the high SST sea surface, with turbulence bringing cold air downwards as the bottom layers warm up, and at the same time sending the top ocean layer downwards as it cools.

Bottom line: Storminess is not needed to retard the onset of freezing in high SST situations. And higher SSTs does not indicate that more heat gets trapped beneath the ice.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Aporia_filia

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Re: "Stupid" Questions :o
« Reply #2703 on: October 24, 2019, 12:13:30 PM »
Provably this is a real stupid question, but can not find a simple explanation of what should(?) be the main physical effect of warming the atmosphere: thermal expansion.
It is always treated when talking about seas.
There are a few papers on 'regional' effects like this https://www.atmos-chem-phys.net/18/15975/2018/
But, how could we spect the atmosphere respond to it, increasing its whole size, only part of it's layers, not the size but total pressure, what happens to the exchange with outer space???

kassy

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Re: "Stupid" Questions :o
« Reply #2704 on: October 24, 2019, 01:59:50 PM »
There are some different effects for the different atmospheric layers. I think you will find more if you look for the effect on specific layers like f.e. the troposphere.

random upper atmosphere example to show why it might be better to look for specific layer + effect of climate change instead of thermal expansion:
http://www.realclimate.org/index.php/archives/2006/11/the-sky-is-falling/

ETA:
https://phys.org/news/2006-12-climate-affecting-earth-outermost-atmosphere.html

Another example and fine links below too.
« Last Edit: October 24, 2019, 04:33:01 PM by kassy »
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binntho

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Re: "Stupid" Questions :o
« Reply #2705 on: October 24, 2019, 02:36:16 PM »
The stratosphere is cooling down as the troposphere warms up, apparently one of the tell-tale signs of greenhous-induced global warming, so perhaps the total atmospheric volume is not changing all that much due to warming?

https://skepticalscience.com/Stratospheric_Cooling.html

The Hadley cell is apparently expanding, see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4378390/

Changes in cloud height could be a symptom of troposphere expansion - apparently cloud height drops in La Nina years rises in El Nino years, but is it trending upwards? Some research says no, a paper from 2012 seems to be saying that the cloud base is dropping, but then I re-found this paper from 2016 that finds that clouds are moving upwards and polewards due to global warming: https://www.nature.com/articles/nature18273
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Alumril

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Re: "Stupid" Questions :o
« Reply #2706 on: October 24, 2019, 03:34:08 PM »
I'm looking for recent methane concentration data from the Tiksi weather station, but the most recent data I can find on the NOAA website is over a year old.

Is the station still operational? Is NOAA still collecting this data? Or am I just being impatient?
« Last Edit: October 24, 2019, 11:39:43 PM by Alumril »

Aporia_filia

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Re: "Stupid" Questions :o
« Reply #2707 on: October 24, 2019, 08:22:07 PM »
Thanks a lot, you two.

RoxTheGeologist

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Re: "Stupid" Questions :o
« Reply #2708 on: October 24, 2019, 10:00:19 PM »
Have you all forgot the basics of sea ice formation? RoxTheGeologids, macid, slow wing?

Sea ice is densest at freezing point, and thus does not freeze in the same way that lake ice does. So slow wings "model" is patently wrong, and the increased density of surface waters as they cool and sink create enough convection to stir up the top tens of meters of ocean, getting all that heat to the surface.

Which is not to say that wave action will also create turbulence.

The current ice-free areas have a fair amount of wind according to NullSchool, but more importantly, the air temps are nowhere near low enough to start freezing.

I think that's what I said. I don't understand where I went wrong with my statement. Please edify!

binntho

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Re: "Stupid" Questions :o
« Reply #2709 on: October 25, 2019, 07:45:40 AM »
Have you all forgot the basics of sea ice formation? RoxTheGeologids, macid, slow wing?

Sea ice is densest at freezing point, and thus does not freeze in the same way that lake ice does. So slow wings "model" is patently wrong, and the increased density of surface waters as they cool and sink create enough convection to stir up the top tens of meters of ocean, getting all that heat to the surface.

Which is not to say that wave action will also create turbulence.

The current ice-free areas have a fair amount of wind according to NullSchool, but more importantly, the air temps are nowhere near low enough to start freezing.

I think that's what I said. I don't understand where I went wrong with my statement. Please edify!

Well, that's not what I read. In this comment,

As ice forms the ice is fresher than the seawater, the salts partitioning into the water. The denser cold, salty water sinks, creating convection. This causes the upper mixed layer to, well, mix, and deepen.  My guess is that it slows down the ice formation, but the mechanism needs ice to be growing before heat starts to move up from deeper layers.

you talk about the formation of ice as causing the sinking of the upper layers, and you claim that ice not only needs to form but needs to be growing before heat starts to move up.

So you are claiming a mechanism for heat transfer to the surface that is based on salt extrusion when ice forms (more salt = more weight).

But the fundamental mechanism of sea ice formation (which you seem to have forgotten here) is that sea water is densest at freezing point, which means that before any ice has time to form, the surface water starts sinking and mixing downwards, and the underlying warmer waters start to move up.

This is presumably what is happening in all the open areas of the arctic right now. Very cold air is blowing in from the south (from Siberia) and from the ice itself, but the air heats up very rapidly over the open ocean where the sea surface temperatures are above freezing.

The first image below shows status this morning from Nullschool, but it's essentially unchanged over the last week or so. The two blue arrows show where cold winds are blowing in over open ocean. The red figures show air temperatures at surface (in Centigrades), and the one in the middle has sea surface temperatures in paranthesis.

The thing to notice is that the air warms very considerably when blowing in over the (much warmer) ocean and that the surface of the ocean is hovering just over the freezing poing of c.a. -1.8C. As I said, this situation has been unchanged this week every time I've checked.

The second image is a very crude attempt at describing the movement of air and water at the interface. Cold air flows in over the warmer ocean, causing the air to get warmer and start to rise, allowing other cold air to sink towards the surface. The wind is carrying this turbulence forward all the time.

At the same time, the relatively static ocean waters cool at the surface and start sinking, allowing warmer deeper waters to rise.

This will continue until there is not enough heat within easy reach to keep the near-freezing waters from sinking before they freeze. This can happen because the ocean has run out of heat, or when the air is cold enough to override the sinking process (at the anecdotal -11C).

The wind is very important here, it keeps carrying the heat away from the surface, and will of couse also increase the water turbulance through wave action.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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oren

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Re: "Stupid" Questions :o
« Reply #2710 on: October 25, 2019, 04:20:04 PM »
I'm looking for recent methane concentration data from the Tiksi weather station, but the most recent data I can find on the NOAA website is over a year old.

Is the station still operational? Is NOAA still collecting this data? Or am I just being impatient?
Welcome to the forum Alumril. (Sorry I can't answer your question).

RoxTheGeologist

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Re: "Stupid" Questions :o
« Reply #2711 on: October 25, 2019, 06:35:24 PM »

...
But the fundamental mechanism of sea ice formation (which you seem to have forgotten here) is that sea water is densest at freezing point, which means that before any ice has time to form, the surface water starts sinking and mixing downwards, and the underlying warmer waters start to move up.

This is presumably what is happening in all the open areas of the arctic right now. Very cold air is blowing in from the south (from Siberia) and from the ice itself, but the air heats up very rapidly over the open ocean where the sea surface temperatures are above freezing.
..


Isn't the mixed layer in summer salinity stratified? Salinity has a much greater impact on density than temperature. I thought that the freshwater lens from melting ice effectively prevented any convection, maybe if the water to 10m (?) has been warmed and homogenized it will turn over as the surface cools.

Sadly we don't have enough buoy data to really get a good picture of what is happening to seas like the Chukchi, distant from rivers, and with much longer exposure to wave and current action because of the early ice loss. It might be that as the sea becomes ice free for longer, the ocean becomes homogenized to deeper levels, evaporation concentrates salt in the surface, sea ice takes longer to form and is thinner and works as a positive feedback year on year.

And no, I didn't suddenly forget the properties of salt water :) If it were freshwater, the warming and melting in the spring would cause the water column to turn over (like a temperate lake).


 

binntho

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Re: "Stupid" Questions :o
« Reply #2712 on: October 26, 2019, 06:06:46 AM »
Isn't the mixed layer in summer salinity stratified? Salinity has a much greater impact on density than temperature. I thought that the freshwater lens from melting ice effectively prevented any convection, maybe if the water to 10m (?) has been warmed and homogenized it will turn over as the surface cools.
I'm pretty sure the mechanism I described does not reach much further than 10m if at that. I'm talking about the very top of the ocean. And any stretch of ocean that has been ice free for months will of course have a "normal" ocean surface, the freshwater from the previous melt having long since been mixed back.

Don't forget that the ocean is vastly more voluminous than the thin skin of ice that forms on top. It's heat content is vastly bigger than the overlying air column. And last but not least, as soon as ice does start to form, the phase change releases significant amounts of heat.

Quote
And no, I didn't suddenly forget the properties of salt water :) If it were freshwater, the warming and melting in the spring would cause the water column to turn over (like a temperate lake).

Well you did seem to forget the one pertinent fact since you didn't mention it in your attemt at a theory for how heat transfer can happen in the top layers of ocean at the onset of the freezing season. Which is what this is all about.

And to be absolutely clear: My explanation above is not a private pet theory, but what has been repeatedly explained to us footlings in this forum by wiser and more knowledgeable members over the years. A very similar discussion to this one took place almost exactly a year ago, here is what I wrote at the time:

It seems that the "-11" or "-10" degrees needed before sea ice forms discussion is doomed to repeat it self regularly. As we apparently all know by now, this is not based on scientific fact but on the close observations of a single individual who seems to know what he was doing.

Those of us who have direct experience of cold climates are aware that sea-ice does not usually form in mildly frosty weather. Around the coast of Iceland sea-ice never forms, except in very rare cases in sheltered harbours, but then again winter temperatures along the coastline very rarely fall below -5 degrees C.

In Denmark, sea-ice does form every few years during prolonged cold spells where temperatures over land fall well below -10 degrees for several days running. Sea-ice starts to grow in harbours and sheltered inlets along the east coast, where there is little to no wave action, but never along the more exposed west coast.

So my pesonal experience of cold-but-not-arctic environments tells me that air temperatures of e.g. -5 are not enough to start sea ice formation in open water. But I must admit that I have no idea whether -5 is enough to start ice growing between ice floes.

Once again a vista of ignorance opens up, begging for the intrepid explorer to chart and measure.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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kassy

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Re: "Stupid" Questions :o
« Reply #2713 on: October 28, 2019, 02:17:17 PM »
2016 features rather prominently on the extent graphics.

Why was that year so bad for extent? What is the short story of 2016?

And related: if i were to read back the 2016 melt thread or ASIB posts is there a good month to start?

I know this sounds like a weird question but 2015 and 2016 were really bad years for me so somehow the info ended up buried.   
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Niall Dollard

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Re: "Stupid" Questions :o
« Reply #2714 on: October 28, 2019, 03:49:52 PM »
2016 features rather prominently on the extent graphics.

Why was that year so bad for extent? What is the short story of 2016?


Short story from Nevens blog.

kassy

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Re: "Stupid" Questions :o
« Reply #2715 on: October 29, 2019, 01:49:41 PM »
Yes, the October blog post + melting season in images was enough.
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PragmaticAntithesis

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Re: "Stupid" Questions :o
« Reply #2716 on: October 30, 2019, 04:48:25 PM »
I've been looking at the extent, area and volume graphs and, over the last week, extent has rose very rapidly. However, area is rising at a much slower pace relative to other years (but still enough to overtake 2016), and volume is still the lowest in the satellite record by a large margin.

Why are the three metrics showing wildly different results despite the fact they're measuring roughly the same thing (how much ice is in the arctic)?

Tom_Mazanec

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Re: "Stupid" Questions :o
« Reply #2717 on: November 01, 2019, 12:50:20 AM »
Well, for one thing, all the MYI is gone now.
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kassy

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Re: "Stupid" Questions :o
« Reply #2718 on: November 01, 2019, 10:23:05 AM »
Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method.

A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated.

and more on:
http://nsidc.org/arcticseaicenews/faq/#area_extent
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Klondike Kat

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Re: "Stupid" Questions :o
« Reply #2719 on: November 01, 2019, 02:31:10 PM »
Yes Kassy.  Additionally, extent and area show the largest divergence during the late summer and early autumn months, as larger ocean surfaces show enough ice to be considered ice-covered in the extent measurements, but are not fully ice covered for the area measurements.  Slush qualifies as ice-covered for extent measurements, but only partially in the area measurements.  During late winter, extent and area measurements converge as most of the surface is ice-covered.  NSIDC prefers using extent as the measurements have been more consistent over time (area measurements tend to fluctate more due to thin ice and melt ponds).

Volume is calculated using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).  The model incorporates sea ice thickness, calculated using the HYCOM-CICE model developed by DMI and sea ice concentration (different from extent or area).  Consequently, volume can differ significantly from either area or extent. 

PragmaticAntithesis

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Re: "Stupid" Questions :o
« Reply #2720 on: November 01, 2019, 08:38:28 PM »
Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method.

A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated.

and more on:
http://nsidc.org/arcticseaicenews/faq/#area_extent

Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method.

A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated.

and more on:
http://nsidc.org/arcticseaicenews/faq/#area_extent

Thanks for the answers!

oren

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Re: "Stupid" Questions :o
« Reply #2721 on: November 07, 2019, 10:56:34 AM »
A small but important correction, PIOMAS does not use the Hycom-CICE model.

PragmaticAntithesis

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Re: "Stupid" Questions :o
« Reply #2722 on: November 07, 2019, 03:29:22 PM »
A small but important correction, PIOMAS does not use the Hycom-CICE model.

That leaves the obvious question: What does is use?

kassy

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Re: "Stupid" Questions :o
« Reply #2723 on: November 09, 2019, 04:23:41 PM »
Model and Assimilation Procedure
PIOMAS is a numerical model with components for sea ice and ocean and the capacity for assimilating some kinds of observations. For the ice volume simulations shown here, sea ice concentration information from the NSIDC near-real time product are assimilated into the model to improve ice thickness estimates and SST data from the NCEP/NCAR Reanalysis are assimilated in the ice-free areas.  NCEP/NCAR reanalysis SST data are based on the global daily high-resolution Reynolds SST analyses using satellite and in situ observations (Reynolds and Marsico, 1993; Reynolds et al., 2007). Atmospheric information to drive the model, specifically wind, surface air temperature, and cloud cover to compute solar and long wave radiation are specified from the NCEP/NCAR reanalysis. The pan-Arctic ocean model is forced with input from a global ocean model at its open boundaries located at 45 degrees North.

http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/
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oren

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Re: "Stupid" Questions :o
« Reply #2724 on: November 09, 2019, 05:54:31 PM »
Thank you Kassy. I was in a rush so gave no details.

Here's some additional information:
Quote
Model

A Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) is used for this project. PIOMAS is a coupled Parallel Ocean and sea Ice Model (POIM, Zhang and Rothrock 2003) with capabilities of assimilating ice concentration and velocity data. It is formulated in a generalized orthogonal curvilinear coordinate (GOCC) system and designed to run on computers with a single processor or massively parallel processors. PIOMAS couples the Parallel Ocean Program (POP) with a thickness and enthalpy distribution (TED) sea-ice model. The POP model is developed at the Los Alamos National Laboratory. 

The TED sea-ice model is a dynamic thermodynamic model that also explicitly simulates sea-ice ridging. The model originates from the Thorndike et al. (1975) thickness distribution theory and is recently enriched by enthalpy distribution theory (Zhang and Rothrock, 2001). It has 12 categories each for ice thickness, ice enthalpy, and snow ((Zhang et al., 2000). This multicategory TED model consists of seven main components: a viscous-plastic ice rheology that determines the relationship between ice internal stress and ice deformation (Hibler 1979), a mechanical redistribution function that determines ice ridging (Thorndike et al. 1975; Rothrock, 1975; Hibler, 1980), a momentum equation that determines ice motion, a heat equation that determines ice growth/decay and ice temperature, an ice thickness distribution equation that conserves ice mass (Thorndike et al. 1975; Hibler, 1980), an ice enthalpy distribution equation that conserves ice thermal energy (Zhang and Rothrock, 2001), and a snow thickness distribution equation that conserves snow mass (Flato and Hibler, 1995). The ice momentum equation is solved using Zhang and Hibler's (1997) ice dynamics model that employs a line successive relaxation technique with a tridiagonal matrix solver, which has been found to be particularly useful for parallel computing (Zhang and Rothrock, 2003). The heat equation is solved over each ice thickness category using a modified three-layer thermodynamic model (Winton, 2000). The configuration of the finite-difference grid of PIOMAS is shown below. 



The model grid is a stretched GOCC grid with the northern grid pole displaced into Greenland. This causes the model to have its highest resolution in the Greenland Sea, Baffin Bay, and the eastern Canadian Archipelago. This lets the model have a reasonably good connection between the Arctic Ocean and the Atlantic Ocean via the Greenland-Iceland-Norwegian (GIN) Sea and the Labrador Sea. The mean horizontal resolution is 22 km for the Arctic, Barents, and GIN (Greenland-Iceland-Norwegian) seas, and Baffin Bay. The model is one-way nested to a global POIM (GIOMAS) by imposing open boundary conditions along the southern boundaries (~ 43oN). Monthly output from GIOMAS is used for the open boundary conditions. The model was driven by the NCEP/NCAR reanalysis data. 

http://psc.apl.washington.edu/zhang/IDAO/model.html

Tom_Mazanec

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Re: "Stupid" Questions :o
« Reply #2725 on: November 11, 2019, 07:16:20 PM »
Why do they call it the Antarctic Peninsula, instead of the Palmer Peninsula like when I was in school?
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blumenkraft

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Re: "Stupid" Questions :o
« Reply #2726 on: November 11, 2019, 07:20:10 PM »
Quote
The Antarctic Peninsula, known as O'Higgins Land in Chile, Tierra de San Martin in Argentina, and originally known as the Palmer Peninsula in the US and as Graham Land in Great Britain, is the northernmost part of the mainland of Antarctica, located at the base of the Southern Hemisphere.

Looks like they told you an American centric worldview in school.

Who would have thought so? ;)
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Re: "Stupid" Questions :o
« Reply #2727 on: November 11, 2019, 09:40:56 PM »
I vote O'Higgin's Land .. home of the wayward Irishman .. :) b.c.
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PragmaticAntithesis

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Re: "Stupid" Questions :o
« Reply #2728 on: November 13, 2019, 08:45:07 PM »
Regarding JAXA's ice measurements: how do they measure the ice area and extent from space when the ice is under cloud cover? Why don't the clouds block the signals?

Iknownot

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Re: "Stupid" Questions :o
« Reply #2729 on: November 15, 2019, 04:45:51 AM »
Hello, I am totally new to this arena, as I only became interested in this during the last few months after I learned of the mosaic expedition, but I am deeply intrigued by this all. I have been reading threads here, and have some questions. Please be kind, as I don't know or understand much of the science behind the arctic but really want to learn. First, is it true there was an earthquake in the arctic, and if so, what does the landscape look like now compared to before? How does it change the currents deep in the oceans?

Thank you.

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Re: "Stupid" Questions :o
« Reply #2730 on: November 17, 2019, 12:03:40 PM »
Regarding JAXA's ice measurements: how do they measure the ice area and extent from space when the ice is under cloud cover? Why don't the clouds block the signals?

The radiometer measures microwave emission.

Quote
The Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the GCOM-W1 satellite is a remote sensing instrument for measuring weak microwave emission from the surface and the atmosphere of the Earth. From about 700 km above the Earth, AMSR2 provides us highly accurate measurements of the intensity of microwave emission and scattering. The antenna of AMSR2 rotates once per 1.5 seconds and obtains data over a 1450 km swath. This conical scan mechanism enables AMSR2 to acquire a set of daytime and nighttime data with more than 99% coverage of the Earth every 2 days. AMSR2 is a successor to AMSR on Japanese ADEOS-II and AMSR-E on Aqua, a NASA satellite.
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blumenkraft

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Re: "Stupid" Questions :o
« Reply #2731 on: November 17, 2019, 12:15:03 PM »
First, is it true there was an earthquake in the arctic, and if so, what does the landscape look like now compared to before? How does it change the currents deep in the oceans?

Hi there. Nice to meet you. :)

There is a website i check on a daily basis [1] regarding earthquakes. There was a 5.1 near Svalbard a couple of weeks ago IIRC. Nothing serious at all. Expect nothing from it to happen.

[1] https://earthquake.usgs.gov/earthquakes/map
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SteveMDFP

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Re: "Stupid" Questions :o
« Reply #2732 on: November 17, 2019, 06:49:49 PM »
First, is it true there was an earthquake in the arctic, and if so, what does the landscape look like now compared to before? How does it change the currents deep in the oceans?

Hi there. Nice to meet you. :)

There is a website i check on a daily basis [1] regarding earthquakes. There was a 5.1 near Svalbard a couple of weeks ago IIRC. Nothing serious at all. Expect nothing from it to happen.

[1] https://earthquake.usgs.gov/earthquakes/map

Exactly.  The spreading fault that forms the mid-atlantic ridge extends north, through Iceland, and up to near Svalbard.  These spreading ridges have occasional earthquakes, but essentially never with significant destruction or tsunamis.

In places in Iceland, you can stand with one foot on the North American Plate and the other on the European.  Iceland is slowly getting wider as a result.  The active vulcanism in Iceland is thought to have more to do with a mantle hot spot than the presence of the spreading fault. 

Mostly, the arctic is pretty quiescent in regards to earthquakes.  Alaska is an exception.

Iknownot

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Re: "Stupid" Questions :o
« Reply #2733 on: November 18, 2019, 02:16:28 AM »
Thanks! So if there's a major earthquake, such as the one the off of the coast of Japan, how does that change the oceans currents? Aren't they all connected in some way, so a major change in one would eventually lead to changes in others?

binntho

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Re: "Stupid" Questions :o
« Reply #2734 on: November 18, 2019, 06:06:14 AM »
Exactly.  The spreading fault that forms the mid-atlantic ridge extends north, through Iceland, and up to near Svalbard.  These spreading ridges have occasional earthquakes, but essentially never with significant destruction or tsunamis.

In places in Iceland, you can stand with one foot on the North American Plate and the other on the European.  Iceland is slowly getting wider as a result.  The active vulcanism in Iceland is thought to have more to do with a mantle hot spot than the presence of the spreading fault. 

Mostly, the arctic is pretty quiescent in regards to earthquakes.  Alaska is an exception.

Quite right. Volcanic activity in Iceland is mostly due to a mantle plume (or hot spot) which has pushed this part of the ocean floor up. The rest of the Mid-Atlantic ridge is at several thousand meters' depth.

Icelandic volcanic hotspot activity apparently translates into an eruption every 4 years or so, most of which are fairly small, which seems to be a typical frequency for hotspots (such as has been calculated for the Ethiopian highland trap series). Hotspot activity can also translate into continuous eruptive activity (as in Hawaii and the Anakil depression)
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kassy

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Re: "Stupid" Questions :o
« Reply #2735 on: November 18, 2019, 03:56:40 PM »
Thanks! So if there's a major earthquake, such as the one the off of the coast of Japan, how does that change the oceans currents? Aren't they all connected in some way, so a major change in one would eventually lead to changes in others?

An earthquake usually does not change anything on a larger scale because other mechanisms drive the ocean currents. Those are very much connected but for a start see

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

https://www.noaa.gov/education/resource-collections/ocean-coasts-education-resources/ocean-currents
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Re: "Stupid" Questions :o
« Reply #2736 on: November 18, 2019, 05:50:19 PM »
How significant was deforestation in pre-industrial and early industrial times, first in Europe and then in the United States, compared to early coal burning, in raising CO2?
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Re: "Stupid" Questions :o
« Reply #2737 on: November 18, 2019, 06:41:19 PM »
How significant was deforestation in pre-industrial and early industrial times, first in Europe and then in the United States, compared to early coal burning, in raising CO2?
Before the industrial revolution - probably deforestation - 49 million km2 (5 times the area of the USA)
Since the industrial revolution - coal

History of coal mining - Wikipedia
https://en.wikipedia.org › wiki › History_of_coal_mining
Total coal output soared until 1918; before 1890, it doubled every ten years, going from 8.4 million short tons in 1850 to 40 million in 1870, 270 million in 1900, and peaking at 680 million short tons in 1918.

https://www.britannica.com/science/deforestation
Conversion of forests to land used for other purposes has a long history. Earth’s croplands, which cover about 49 million square km (18.9 million square miles), are mostly deforested land. Most present-day croplands receive enough rain and are warm enough to have once supported forests of one kind or another. Only about 1 million square km (390,000 square miles) of cropland are in areas that would have been cool boreal forests, as in Scandinavia and northern Canada. Much of the remainder was once moist subtropical or tropical forest or, in eastern North America, western Europe, and eastern China, temperate forest.

Modern Deforestation
The United Nations Food and Agriculture Organization (FAO) estimates that the annual rate of deforestation is about 1.3 million square km per decade, though the rate has slowed in some places in the early 21st century as a result of enhanced forest management practices and the establishment of nature preserves. The greatest deforestation is occurring in the tropics, where a wide variety of forests exists. They range from rainforests that are hot and wet year-round to forests that are merely humid and moist, to those in which trees in varying proportions lose their leaves in the dry season, and to dry open woodlands. Because boundaries between these categories are inevitably arbitrary, estimates differ regarding how much deforestation has occurred in the tropics.
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Re: "Stupid" Questions :o
« Reply #2738 on: November 18, 2019, 07:40:40 PM »
How significant was deforestation in pre-industrial and early industrial times, first in Europe and then in the United States, compared to early coal burning, in raising CO2?

I have read in Callum Roberts' "The Unnatural History Of The Sea" that in the USA when the civilisation humans arrived in the 15th century, they found an almost pristine living nature. The same as it was in Northern Europe 1500 years earlier.
I have also read "A squirrel would be able to go from the east to the west coast and not leave the trees".

edit: corrected Mr.Roberts name
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Re: "Stupid" Questions :o
« Reply #2739 on: November 18, 2019, 08:46:48 PM »
Study reveals environmental impact of American Indian farms centuries before Europeans arrived in North America
In Anthropology, Research News, Science & Nature / 9 May 2011
Quote
New evidence gathered from sediments along the Delaware River in Pennsylvania is drastically revising theories about land use by Native Americans and the impact they once had on their environment. The new research reveals that from the period between 1100-1600 small agricultural settlements up and down the Delaware River Valley caused a 50-percent increase in sediment runoff into the Delaware River. This was done primarily by burn-clearing of as much as half of the forest-cover along the Delaware’s banks.

Baylor Study Shows Native Americans Significantly Modified American Landscape Years Prior to the Arrival of Europeans
March 21, 2011
Quote
Study has important implications to how "sensitive" landscapes are to land-use and farming strategies

(Waco, Texas - March 21, 2011) A new study by Baylor University geology researchers shows that Native Americans' land use nearly a century ago produced a widespread impact on the eastern North American landscape and floodplain development several hundred years prior to the arrival of major European settlements.

The study appears on-line in the journal Geology.

The Pristine Myth: The Landscape of the Americas in 1492
William M. Denevan

Department of Geography, University of Wisconsin, Madison, WI 53706  [1992]

Quote
Abstract.
The myth persists that in 1492 the Americas were a sparsely populated wilderness, -a world of barely perceptible human disturbance.- There is substantial evidence, however, that the Native American landscape of the early sixteenth century was a humanized landscape almost everywhere. Populations were large. Forest composition had been modified, grasslands had been created, wildlife disrupted, and erosion was severe in places. Earthworks, roads, fields, and settlements were ubiquitous. With Indian depopulation in the wake of Old World disease, the environment recovered in many areas. A good argument can be made that the human presence was less visible in 1750 than it was in 1492.
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Re: "Stupid" Questions :o
« Reply #2740 on: November 18, 2019, 09:16:20 PM »
TB:
Was it less noticeable in 1750 than in 1492 because of smallpox?
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Re: "Stupid" Questions :o
« Reply #2741 on: November 18, 2019, 10:04:25 PM »
TB:
Was it less noticeable in 1750 than in 1492 because of smallpox?
You will find it Gutenberg.org (the original free e-books site) a book by Robert W. Chambers - "The Hidden Children". It's very different for its time in its tone of regret for the passing of Native American society.

Written in 1913, it is set in the years of the US War of Independence. During that time, the British sought and made an alliance with a number of Native American Nations known as "The League", which sealed its fate.** An expedition was mounted by the rebels to destroy the main settlement of the Native Americans (I'm a Brit) due to the Native Americans successes against the settlers in Independence leaning regions.

The books describes the considerable area between the East Coast west as far as the Great Lakes. Though settled by the Native Americans, it was still mainly virgin forest. Though fiction, the description is convincing.
__________________________________________________
And I quote from the preface:-

**"Perhaps of all national alliances ever formed, the Great Peace, which is called the League of the Iroquois, was as noble as any. For it was a league formed solely to impose peace. Those who took up arms against the Long House were received as allies when conquered—save only the treacherous Cat Nation, or Eries, who were utterly annihilated by the knife and hatchet or by adoption and ultimate absorption in the Seneca Nation. "

As for the Lenni-Lenape, when they kept faith with the League they remained undisturbed as one of the "props" of the Long House, and their role in the Confederacy was embassadorial, diplomatic and advisory—in other words, the role of the Iroquois married women. And in the Confederacy the position of women was one of importance and dignity, and they exercised a franchise which no white nation has ever yet accorded to its women.
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Re: "Stupid" Questions :o
« Reply #2742 on: November 19, 2019, 02:53:50 AM »
Does anybody have an idea when this article was written?
http://globalwarming.berrens.nl/globalwarming.htm
I ask because:
1) There is a date given. It is today's date. It is always today's date. It was the date I put the article in my Bookmarks awhile ago when I put it in.
2) There is this sentence in it:
Quote
Chance of avoiding two degrees of global warming: 93%, but only if emissions of greenhouse gases are reduced by 60% over the next 10 years.
If this article was written in 2018, that is one thing. If it was written in 2008, that is something else.
Anybody know?
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Re: "Stupid" Questions :o
« Reply #2743 on: November 19, 2019, 03:15:09 AM »
TB:
Was it less noticeable in 1750 than in 1492 because of smallpox?

Not just smallpox but many diseases introduced from Europe such as paratyphoid.  The Aztec population was reduced to about 10% of its former value following the european invasion, for example.  In the 1545 outbreak about 15 million died over a period of 5 years. One Franciscan friar wrote “Nobody had the health or strength to help the diseased or bury the dead. In the cities and large towns, big ditches were dug, and from morning to sunset the priests did nothing else but carry the dead bodies and throw them into the ditches.”
In Florida there were about 700,000 native americans in 1520 by 1700 there were ~2,000, similar events happened all over america.  There are some suggestions that following the great reduction in the plains indians that the buffalo population expanded greatly.

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Re: "Stupid" Questions :o
« Reply #2744 on: November 19, 2019, 03:18:01 AM »
Does anybody have an idea when this article was written?
http://globalwarming.berrens.nl/globalwarming.htm
I ask because:
1) There is a date given. It is today's date. It is always today's date. It was the date I put the article in my Bookmarks awhile ago when I put it in.
2) There is this sentence in it:
Quote
Chance of avoiding two degrees of global warming: 93%, but only if emissions of greenhouse gases are reduced by 60% over the next 10 years.
If this article was written in 2018, that is one thing. If it was written in 2008, that is something else.
Anybody know?

I think you'll find that it was January 25th 2018

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Re: "Stupid" Questions :o
« Reply #2745 on: November 19, 2019, 03:28:17 AM »
And I think you'll find that the chances of avoiding two degrees are closer to 7% than to 93%.

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Re: "Stupid" Questions :o
« Reply #2746 on: November 19, 2019, 03:41:53 AM »
Thanks, Phil (how did you find that out)?
And oren, read the quote. It says if. But we just might not escape two degrees even if that miraculous reduction occurs. The chances are 93% even in the event of a 60% reduction in emissions. Of course, the chances of those reductions occurring in the first place are probably less than 7%.
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Phil.

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Re: "Stupid" Questions :o
« Reply #2747 on: November 19, 2019, 06:26:39 AM »
Thanks, Phil (how did you find that out)?

I copied the title and did a Google search for it and found the original.

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Re: "Stupid" Questions :o
« Reply #2748 on: November 19, 2019, 07:58:08 AM »
How significant was deforestation in pre-industrial and early industrial times, first in Europe and then in the United States, compared to early coal burning, in raising CO2?

There is a school of thought that claims that human activities have been affecting the climate since the start of agriculture. Deforestation (and reforestation) are amongst the biggest factors considered, but also advances in agriculture that have the potential to increase drastically the amount of CO2 released from non-forested areas (e.g. rice cultivation) besides leading to population expansion and increase deforestation.

Deforestation is a result of increased population, and significant population decrease leads to reforestation. The 15th and 16th centuries probably saw signficant reforestation due to large drops in population, mostly caused by Europeans and their new ships. Starting in Western Africa, but moving into a much higher gear once it reached the Americas, this reforestation could well be the main driver behind the 0.25 degrees dip in global temperatures that occured between the "medieaval warm period" and the "little ice age", one of the biggest Holocene temperature swings until our current one.

The mediaval warm period, on the other hand, could well have had its' causes in significant deforestation in Eurasia due to the spread of new agricultural methods (mainly crop rotation) resulting in a signifcant population increase following the precipitous drop in population that occurred at the end of the classical period.

Another period of rapid population increase was in Imperial Roman times, and there was a minor warm period that followed. On the other hand, the plagues of the 6th century severely reduced the Eurasian population, and there was a cold spell shortly after.

So yes, there is ample circumstantial evidence that deforestation (and reforestation) caused by human activities has had a significant effect on global temperatures in the past.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Phil42

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Re: "Stupid" Questions :o
« Reply #2749 on: November 19, 2019, 08:18:07 AM »
Just a quick question that shouldn't interrupt any discussion.

In the Sentinel images in the "PIG has calved" thread, there are always dates on the images displaying from when they are. How does one turn those date labels on in the Sentinel-hub EO-Browser?