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Antarctica 2018

Antarctica 2018

Unread postby Tanada » Sun 18 Feb 2018, 11:59:03

A nice album of photos in link below the quote.
Douglas Fox wrote:
PUBLISHED February 16, 2018

Scientists have peered into one of the least-explored swaths of ocean on Earth, a vast region located off the coast of West Antarctica. It is locked beneath a crust of ice larger than Spain and more than 1,000 feet thick, making its waters perpetually dark—and extremely difficult for humans to access. Now, a team of researchers has bored a hole through the ice and sampled the ocean beneath it. Their work could shed light on a poorly understood, but ominous episode in Antarctica’s recent past.

A team of scientists from New Zealand began this two-month expedition in November. A ski-mounted Twin Otter aircraft ferried them 220 miles from the nearest base, landing near the middle of the Ross Ice Shelf—the massive slab of ice and snow, as flat and empty as a prairie, that hangs off the coastline of West Antarctica and floats on the ocean. Amid the glow of 24-hour summer sunlight filtering down through fog, they assembled an automobile-sized contraption of pipes, hoses, and boilers. (See more of the world below Antarctic ice.)

This machine generated a powerful jet of hot water, which they used to melt two narrow holes, each a few inches across, more than 1,100 feet down to the bottom of the ice. They then lowered cameras and other instruments through the holes, into the waters below. In doing so, they hoped to answer a question of worldwide importance: just how secure is the ice of West Antarctica?

The West Antarctic Ice Sheet is up to 10,000 feet thick in some places. It sits in a broad, low bowl that dips thousands of feet below sea level—making it vulnerable to deep, warm ocean currents that are already nipping at its outer edges. It is stabilized, at least for the time being, by a phalanx of floating ice shelves, that hang off its outer edges—of which the Ross Ice Shelf is by far the largest. Those floating shelves provide a buttress; they “are holding back a very big amount of ice,” says Craig Stevens, an oceanographer from the National Institute of Water and Atmospheric Research in New Zealand, who participated in the expedition.

Global sea levels would rise by 10 feet if West Antarctica lost these crucial stabilizers and spilled its ice into the ocean. Scientists fear that some of these ice shelves are already weakening. Stevens and his colleagues hoped to assess the health of the Ross Ice Shelf by measuring water temperatures and ocean currents beneath it—thereby determining how quickly ice is melting off its underside. (See what would happen if all the world’s ice melted.)
Surprising Finds

The surprises began almost as soon as a camera was lowered into the first borehole, around December 1. The undersides of ice shelves are usually smooth due to gradual melting. But as the camera passed through the bottom of the hole, it showed the underside of the ice adorned with a glittering layer of flat ice crystals—like a jumble of snowflakes—evidence that in this particular place, sea water is actually freezing onto the base of the ice instead of melting it.

“It blew our minds,” says Christina Hulbe, a glaciologist from the University of Otago in New Zealand, who co-led the expedition. The Ross Ice Shelf is considered more stable, at present, than many of West Antarctica’s other floating shelves—and this observation could help explain that: if a few inches of sea water periodically freezes onto the bottom of its ice, this could buffer it from thinning more rapidly.

The new holes drilled through the Ross Ice Shelf also provide a more general window into the unknown. Under the ice shelf “is a huge amount of ocean, it’s the volume of the North Sea” between England and Norway, says Hulbe, “and there are almost no measurements” there.

Only twice before have humans pierced the deep interior of the Ross Ice Shelf to study its underlying ocean. In 1977, researchers drilled through the ice shelf 300 miles in from its seaward edge (about 80 miles inland from the current holes), and in 2015 a team drilled through the back corner of the ice shelf, 500 miles in from its seaward edge. Those studies provided only brief glimpses of how deep, warm water circulates under the ice shelf, covering a few hours or days.
Looking to the Future

This time around, the New Zealand team installed instruments in one of their holes that will monitor ocean currents and water temperatures under the ice for the next two years or so, beaming that information home via satellite link. It’s important to understand these currents, says Stevens, because “if we get the circulation wrong, then we’re getting the melting wrong.”

The new project could also cast light on some lingering suspicions—that even though the Ross Ice Shelf seems stable today, it has actually undergone some dramatic collapses in the recent past. (Learn about the Maine-size hole in Antarctica.)

Reed Scherer made this discovery back in 1998 while studying mud that had been plucked from beneath the West Antarctic Ice Sheet, through another borehole, 100 miles inland from the back edge of the ice shelf.

Scherer, a micro-paleontologist now at Northern Illinois University in DeKalb, found this subglacial mud chockablock full of microscopic diatom shells—beautiful glassy objects, reminiscent of fine vases. They were the ancient remains of photosynthetic organisms that had once lived in the sea before dying and settling to the bottom.

Some of those dead diatoms were only a few hundred thousand years old, leading Scherer to an astounding conclusion: this area, now covered by 3,000 feet of ice, had recently been open sea, bathed in life-sustaining sunlight that could support the diatoms’ growth. This suggested that the entire Ross Ice Shelf, and much of the ice behind it, had collapsed.

The Ross Ice Shelf “has come and gone probably many times in the last million years,” says Scherer. It likely collapsed during a warm period 400,000 years ago. But he believes it could also have collapsed as recently as 120,000 years ago, the last time that temperatures were about as warm as they are today.

The New Zealanders’ project could shed light on this question. One day in December, a cylinder dripping with gray gleaming mud was hoisted out of the borehole, into the bright summer sun—a core plucked from the sea floor, 2,400 feet beneath the drill site. As the scientists analyze that mud, it may yield more diatoms. And that could provide another chance to investigate when this area was free of ice in the past, says Scherer: “I’m very interested to see what the Kiwis find.”


LINK
I should be able to change a diaper, plan an invasion, butcher a hog, design a building, write, balance accounts, build a wall, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, pitch manure, program a computer, cook, fight efficiently, die gallantly. Specialization is for insects.
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Re: Antarctica 2018

Unread postby Plantagenet » Sun 18 Feb 2018, 13:01:10

I just saw a theatrical production of a play set in Antarctica called "Terra Nova" staged here in at our local community theatre in central Alaska. The play dramatizes the doomed Robert Falcon Scott expedition to the south pole.

I really recommend people go see it if the play gets put on in your area. I've been watching TV NATURE specials about Antarctica for years, and am a big fan of Shakleton and Amundson, but seeing real actors stumbling around on stage dressed for the Antarctic and pushing a huge sledge across the stage, and then dying one by one from frostbite, starvation and exhaustion is pretty powerful.

Of course the play had some funny moments for people here in Alaska. The bearded actors are dressed in Antarctic gear with mittens and balaclavas and grimy clothes and faces, but they don't look much different from typical dog mushers and fur trappers and prospectors who live in cabins in central Alaska now. And people in the audience laughed out loud when Scott, Oates and Wilson, dying from frostbite on stage, complain about the bitter cold hitting -40 in Antarctica. We drop to -40 pretty regularly in the winter here in central Alaska, and even had some -50 over the last two weeks during the 1000 mile dog sled race from Dawson to Fairbanks.

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Actors perform in TERRA NOVA---a play about Robert Falcon Scott's doomed trip in Antarctica
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Re: Antarctica 2018

Unread postby Plantagenet » Wed 21 Feb 2018, 18:49:54

New NASA study finds accelerating ice flow into the ocean in West Antarctica, with ice flow in East Antarctica showing no sign of accelerating flow.

antarctic-ice-loss-

....the study found an overall ice discharge for the Antarctic continent of 1,929 gigatons per year in 2015, with an uncertainty of plus or minus 40 gigatons. That represents an increase of 36 gigatons per year, plus or minus 15, since 2008. A gigaton is one billion tons.

The ca. 36 billion tons of extra ice entering the sea each year corresponds to a roughly a 2% increase in discharge into the ocean ocean, for a total increase in ice discharge of ca. 350 billion tons over the last 10 years or so......

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The theory that Antarctica would see a big enough increase in snowfall as the planet warms to show up as a gain in ice is now clearly disproven. Antarctica is losing ice mass---not gaining it.
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Re: Antarctica 2018

Unread postby rockdoc123 » Wed 21 Feb 2018, 23:55:14

The theory that Antarctica would see a big enough increase in snowfall as the planet warms to show up as a gain in ice is now clearly disproven.


Not according to this very recent paper:

Medley, B. et al, 2018. Temperature and Snowfall in Western Queen Maud Land Increasing Faster Than Climate Modle Projections. Geoph Res Let, DOI: 10.1002/2017GL075992

From the conclusions:

We conclude that “anomalous” snowfall gains in QML over recent years, responsible for years of mass gain over EAIS (Shepherd et al., 2012), are likely part of a longer-term trend. Ice core evidence of increased snow accumulation in eastern QML (Philippe et al., 2016) suggests that the pattern might be larger in scale, but a more detailed comparison is necessary to relate the two records. If snow accumulation continues to increase at modern rates (+45% per century), QML snowfall could mitigate sea-level contributions from ice loss in WAIS and the Antarctic Peninsula.


Small biases in the rates of present and future accumulation change yield large uncertainties in AIS mass balance. The P−E trends in CESM-LE simulations are lower than observed accumulation trends, which suggests that future accumulation in western QML is underestimated. Therefore, the mitigating impact of higher snowfall rates is likely not fully resolved. Between 1990–1999 and 2090–2099, snow accumulation over the grounded AIS increases ~1.5 mm SLE yr-1 in CESM-LE, a value approximately half of the current rate of global mean SLR since 1993 (Beckley et al., 2010) and more than 7 times the current rate of mass loss from the entire AIS (Shepherd et al., 2012)
.

There is a clear need for improved evaluation of global atmospheric model performance in Antarctica since accumulation partly controls the ice sheet’s contribution to SLR, which is only possible with more long-term records of accumulation and temperature. Records collected widely across the AIS, covering a substantial portion of the preindustrial through present day, are lacking, yet needed


For comparison sake a 36 GY/yr increase in ice discharge equates to a 0.09 mm SLE/yr equivalent whereas the snow increases suggested above equate to a 1.5 mm SLE/yr. So the jury isn't out yet.
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Re: Antarctica 2018

Unread postby Plantagenet » Thu 22 Feb 2018, 00:27:18

The theory that Antarctica would see a big enough increase in snowfall as the planet warms to show up as a gain in ice is now clearly disproven.


Not according to this very recent paper


That local paper is about one local area in Antarctica. Antarctica is a very big place----you can't take data from one locale or even one region and extrapolate it over the entire continent---there is too much regional variability.

In contrast, the very recent NASA paper presents ice volume data that actually covers the entire continent---and the NASA paper proves the entire continent is losing ice mass every year, i.e. the total amount of ice is shrinking.

Get it now?

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Re: Antarctica 2018

Unread postby drwater » Thu 22 Feb 2018, 15:49:22

Scientific American did a nice article on this whole issue and controversy.:

https://www.scientificamerican.com/article/what-to-believe-in-antarctica-rsquo-s-great-ice-debate/
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Re: Antarctica 2018

Unread postby Plantagenet » Thu 22 Feb 2018, 16:13:27

drwater wrote:Scientific American did a nice article on this whole issue and controversy.:

https://www.scientificamerican.com/article/what-to-believe-in-antarctica-rsquo-s-great-ice-debate/


Thanks drwater. That is indeed a useful summary done by Scientific American.

However, the Scientific American doesn't just discuss the issue--- the Scientific American article reaches its own clear conclusion. After discussing all the data, including some important data that isn't published yet, Scientific American concludes that the scientific consensus is correct, i.e. that Antarctica is losing ice mass and contributing to sea level rise.

The new NASA study I mentioned above provides still more data that supports the scientific consensus, i.e. that Antarctica as a whole is losing ice mass and contributing to sea level rise.

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Re: Antarctica 2018

Unread postby chilyb » Thu 22 Feb 2018, 18:04:30

Hi rockdoc123,

I have to agree with Plantagenet on this one.

Here is the abstract from the paper you cited "Temperature and Snowfall in Western Queen Maud Land Increasing Faster Than Climate Model Projections":

East Antarctic Ice Sheet (EAIS) mass balance is largely driven by snowfall. Recently, increased snowfall in Queen Maud Land led to years of EAIS mass gain. It is difficult to determine whether these years of enhanced snowfall are anomalous or part of a longer-term trend, reducing our ability to assess the mitigating impact of snowfall on sea level rise. We determine that the recent snowfall increases in western Queen Maud Land (QML) are part of a long-term trend (+5.2 ± 3.7% decade−1) and are unprecedented over the past two millennia. Warming between 1998 and 2016 is significant and rapid (+1.1 ± 0.7°C decade−1). Using these observations, we determine that the current accumulation and temperature increases in QML from an ensemble of global climate simulations are too low, which suggests that projections of the QML contribution to sea level rise are potentially overestimated with a reduced mitigating impact of enhanced snowfall in a warming world.


This doesn't say anything about what's happening at the WAIS - specifically with respect to the fast collapse mechanisms that DeConto and Pollard described in their 2016 Nature paper. If I recall correctly, a collapse of the WAIS has the potential to overwhelm any SMB gains due to increasing snowfall.

Regardless of sea level rise, in the 2018 Medley paper, they claim a local area warming between 1998-2016 of +1.1 ± 0.7°C decade−1. I highlighted this above, because it seems, well, significant and rapid.

What do you think?
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Re: Antarctica 2018

Unread postby rockdoc123 » Thu 22 Feb 2018, 18:25:02

That local paper is about one local area in Antarctica. Antarctica is a very big place----you can't take data from one locale or even one region and extrapolate it over the entire continent---there is too much regional variability


Well either you didn't read either paper or you didn't understand what was being said.

The paper you reference (actually you didn't as normal you just link to the press release) is

Gardner, A.S., et al, 2018. Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years. The Cryosphere, 12, pp 521 - 547 .

This paper uses Landsat to evaluate flow rates which is what the paper concentrates on. They do not come up with an estimate of mass budget (outflows versus accumulation) based on incorporation of satellite (Grace) and a GIA model as is normally the case but rather use the regional climate model RACMO2.3 to arrive at what SMB should be for the various areas (i.e. it is not measured directly).

In contrast the Medley et al, 2018 paper I reference above uses actual measurements (ice core data) to assess increasing accumulation rates for Queen Maud Land (which have been documented in a number of papers) and note that it is likely part of a longer-term trend. Because QML makes up the vast majority of positive SMB in mass budget for Antarctica it is all important in understanding potential future sea level contributions. The data from their observations is incorporated into the climate ensemble CESM-LE in order to look at future potential SMB. The point that the authors make is that their results indicate an annual increase in SMB over the grounded Antarctic Ice Sheet of +1.5 mm Sealevel equivalent per year. They correctly point out that that number is approximately half of the current sea level rise since 1993 and more than seven times the rate of mass budget loss from the entire AIS as mentioned in Shepherd, 2012 a paper that has been discussed at length previously. In that paper, Shepherd et al assesses through several methods the net mass budget for the entire AIS of -84 Gt/yr which is 0.23 mm of sea level equivalent rise per year.

Note the difference here. Gardner et al, 2018 use the standard climate model to assess SMB and the paper I referenced Medley eta al, 2018 points out that those models have grossly underestimated SMB as recent continuing increases in snow accumulation are part of a longer term trend. The title of the paper describes this well: Temperature and Snowfall in Western Queen Maud Land Increasing Faster Than Climate Model Projections.

so your claim that:
The theory that Antarctica would see a big enough increase in snowfall as the planet warms to show up as a gain in ice is now clearly disproven.


is falsified by the findings of Medley et al.

And as to the values for mass budget that Garder et al, 2018 come up with something is clearly amiss. Their value of -183 Gt/yr is far and away above all of the previous estimates. It is interesting that in their paper they chose only to compare their estimate with all the higher estimates that have been made over the past decade but fail to include the much smaller estimates that have been made in that same time period, and there are quite a number of them. As an example they actually reference Harig et al, 2015 for another reason but fail to mention that Harig et al's estimate for mass budget was -92 GT/yr almost exactly half of their own estimate. They also ignore Williams et al, 2014 who estimated mass budget for Antarctica was -58 Gt/yr which is on the very low end of all estimates.
But what is very disconcerting about the Gardner et al, 2018 paper is there is something amiss with their maths.

Table 2 which presumably outlays all of the mass balance and budget numbers for the various areas they looked at states the following:

The net mass balance is calculated as the 2008–2015 SMB minus the average rate of discharge minus basal melt. Discharge for 2008 is derived from Rignot et al. (2011a) and for 2015 from the mean of the JPL 2015 error-weighted Landsat velocity mapping.


And for the entirety of Antarctica they note Discharge in Gt/yr for 2008 was 1894 +/- 43 Gt/yr and for 2015 was 1929 +/- 40 Gt/yr. The average of that is 1911 +/- 41 Gt/yr. The SMB that they get from RACMO2.3 is 1834 +/- 94 Gt/yr and basal metl is 63 +/-4 Gt/yr. When you add 1911 and 63 you get 1974 GT/yr of total outflow and when you subtract the positive SMB of 1834 Gt/yr you get -140 Gt/yr not the -183 GT/yr they show. In order to get the -183 Gt/yr the average rate of discharge would have to be 1954 Gt/yr which is higher than the discharge recorded at either end of their distribution (2008 or 2015), so there is something wrong here. A mass budget of -140 Gt/yr is still on the high side of most assessments for Antartica but it is within the range of published assessments. Interesting scaling back to -140 Gt/yr assuming basal melt and SMB are unchanged ends up with a discharge rate that yields an acceleration rate of not far off what Shepherd et al, 2012 came up with and that is half of what Gardener et al come up with.

So there are some issues here. As I have said before there is a very wide range in estimates of surface mass budget for Antarctica based on assessments made from various GIA models and various iterations of GRACE. The authors of these estimates simply report their results and mention them in context of all the other numbers that have been arrived at with the knowledge that there are a lot of unknowns and uncertainties at this point many of which are coming to light only recently (last year a paper published which change the GIA assumptions such that surface mass balance for Antarctica is less negative than previously assumed).
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Re: Antarctica 2018

Unread postby rockdoc123 » Thu 22 Feb 2018, 18:43:24

This doesn't say anything about what's happening at the WAIS - specifically with respect to the fast collapse mechanisms that DeConto and Pollard described in their 2016 Nature paper. If I recall correctly, a collapse of the WAIS has the potential to overwhelm any SMB gains due to increasing snowfall.

Regardless of sea level rise, in the 2018 Medley paper, they claim a local area warming between 1998-2016 of +1.1 ± 0.7°C decade−1. I highlighted this above, because it seems, well, significant and rapid.


Well first off the "fast collapse" as referenced in D&P and discussed at length in this thread previously talks about the future. They have no evidence of that happening now, it is just a postulation at this point.

The reference to warming in the Meley et al paper is in the context of its importance in the climate ensemble they use to model future accumulations. Remember that it has always been postulated that warming will result in increased precipitation which in Antarctica for several hundred years will be in the form of snowfall. Note that they used temperature data from Kohnen station in their model which is slightly warmer than much of Antarctica but still is well below zero for the vast majority of the year.

And the point you don't get about "this is just a regional event" is that the increasing snowfall at Queen Maud Land dominates the mass budget for all of East Antarctica and it is actual hard evidence that model predictions of increased snowfall across Antarctica in a warming climate is correct. The fact that snowfall is increasing much more rapidly than the general climate models predict (the same ones used in the Gardner et al paper) is important to the whole continent and as the Medley correctly point out will mitigate much of the sea level rise coming from Antarctica.

Note that this is no different from what the IPPC said in the last TAR and is consistent with many papers that have been published over the past few years.
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Re: Antarctica 2018

Unread postby Plantagenet » Thu 22 Feb 2018, 19:35:39

the Medley et al, 2018 paper I reference above uses actual measurements (ice core data) to assess increasing accumulation rates for Queen Maud Land


Once again, Queen Maud land is just a small part of a continent called Antarctica.

Once again, you can't extrapolate data from one ice core or even a set of ice cores obtained just from one region over the entire continent.

In contract, the NASA studies I cite use satellite based instruments to actually make repeat high frequency measurements over the entire continent. These repeat measurements clearly show the annual cycle of accumulation and ablation, superimposed on a year to year trend of a net loss of mass due to melting of ice over the entire continent. The satellite gravity data is particularly compelling, IMHO.

Get it now?

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Re: Antarctica 2018

Unread postby Plantagenet » Thu 22 Feb 2018, 19:42:05

chilyb wrote:
I have to agree with Plantagenet on this one.


Your judgement is sound. :lol: :-D 8) :idea:

By the way----you have a scientific background, right chilyb? You're doing a good job of reading the technical literature.

chilyb wrote:Regardless of sea level rise, in the 2018 Medley paper, they claim a local area warming between 1998-2016 of +1.1 ± 0.7°C decade−1. I highlighted this above, because it seems, well, significant and rapid.


That is significant and rapid warming, but not totally unexpected at high latitudes where greenhouse warming is proceeding at significantly higher rates then is being seen at lower latitudes.

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Re: Antarctica 2018

Unread postby chilyb » Thu 22 Feb 2018, 21:16:08

Hi rockdoc123,

Well first off the "fast collapse" as referenced in D&P and discussed at length in this thread previously talks about the future. They have no evidence of that happening now, it is just a postulation at this point.


According to this logic, the WAIS needs to disintegrate before we can begin to validate the DeConto and Pollard paper! LOL!

The reference to warming in the Meley et al paper is in the context of its importance in the climate ensemble they use to model future accumulations. Remember that it has always been postulated that warming will result in increased precipitation which in Antarctica for several hundred years will be in the form of snowfall.


But here it's OK to reference the climate models? Medley et al., states the models are not accurate in the title of their paper! "Temperature and Snowfall in Western Queen Maud Land Increasing Faster Than Climate Model Projections."

Maybe none of the models are accurate!

Note that they used temperature data from Kohnen station in their model which is slightly warmer than much of Antarctica but still is well below zero for the vast majority of the year.


Yes, I get that it is cold in Antarctica. But Medley stated the observed rate of change is both "significant and rapid," correct? Why would they choose the word "significant" if it is still really cold?

The fact that snowfall is increasing much more rapidly than the general climate models predict (the same ones used in the Gardner et al paper) is important to the whole continent and as the Medley correctly point out will mitigate much of the sea level rise coming from Antarctica.


Yes, totally agree. Given there is no rapid retreat of the marine ice sheets that are grounded hundreds of feet below sea level, as we discussed on a previous occasion. Do you agree with that in principle?
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Re: Antarctica 2018

Unread postby rockdoc123 » Thu 22 Feb 2018, 21:48:44

Once again, Queen Maud land is just a small part of a continent called Antarctica. 

Once again, you can't extrapolate data from one ice core or even a set of ice cores obtained just from one region over the entire continent.

OK, obviously I have to talk slowly with you. Perhaps you should read the paper for a change?

QML is where the increase in snowfall has been happening to this point and the increase itself is consistent with models that incorporate warming.
The amount of snowfall in QML alone is what drives the positive mass budget in Eastern Antartica.
The increased snowfall as measured by the cores in QML is used to update the ensemble of computer models that predict snowfall across the entirety of Antarctica. And it is that information that falls out of the paper in question.
The measures are local (the cores) the models where the data are used are regional and continent wide.
The output of their models indicates an increase per year of snowfall of 1.5 mm sea level rise which is somewhere close to 550 Gt/yr increase. It doesn’t matter if that snowfall all lands on the coast or all lands inland or wherever…it offsets sea level rise.
This is pretty basic so I’m not sure why you are confused.

In contract, the NASA studies I cite use satellite based instruments to actually make repeat high frequency measurements over the entire continent. These repeat measurements clearly show the annual cycle of accumulation and ablation, superimposed on a year to year trend of a net loss of mass due to melting of ice over the entire continent. The satellite gravity data is particularly compelling, IMHO.


well first off all you "cited" was a press release that doesn't include a link to the actual paper, one has to go and dig that up on their own but more importantly you did not read the paper. As I stated they use Landsat to measure Discharge. The SMB (snowfall etc) component is derived from the climate model RACMO2/3 published by other authors. The only new thing in this paper is their approach with Landsat and their measurement of flux gates, everything else comes from the existing literature.

This from the paper:

Here we describe the application of two newly developed and independent feature tracking methodologies (JPL and NSIDC) that we applied to hundreds of thousands of Landsat image pairs covering the entire Antarctic ice sheet north of 82.4◦ S, producing six near-complete mappings of ice sheet surface velocities in both the 2013–2014 and 2014–2015 austral polar daylight periods. By differencing these velocity fields with the earlier SAR mapping (Rignot et al., 2011a) we resolve changes in ice surface velocity for the 7-year period between circa 2008 and 2015. Velocity changes are then used to estimate ice discharge on the basin scale and its change through time. For the determination of ice discharge we provide a novel approach to defining the cross-sectional area of ice flow (flux gate; Sect. 2.2) that greatly reduces uncertainties in estimates of ice discharge. By differencing estimates of ice discharge and basal melt rates (Van Liefferinge and Pattyn, 2013) from published estimates of the surface mass balance (van Wessem et al., 2016, 2014) we are able to estimate the net mass balance of the ice sheet on the basin scale, revealing recent patterns of ice sheet imbalance.


They used radio echo sounding to determine the flux gates, and they used Cryosat 2 radar altimetry to look at surface elevation change (which goes into the basal melt calculation).

And apparently your humble opinion isn’t worth crap given they never used gravity data in their analysis, it is never mentioned in the paper and it never appears anywhere. The only time the word “gravity” appears in the entire paper is where they are referencing the work of other authors which they ignore. So you are either living on another world or referencing the wrong paper.
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Re: Antarctica 2018

Unread postby chilyb » Thu 22 Feb 2018, 21:57:52

Hi Plantagenet,

Here is the link to the NASA satellite study you referenced above:

https://www.the-cryosphere.net/12/521/2018/

From the abstract:
The West Antarctic Ice Sheet is experiencing high rates of mass loss and displays distinct patterns of elevation lowering that point to a dynamic imbalance. We find modest increase in ice discharge over the past 7 years, which suggests that the recent pattern of mass loss in Antarctica is part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent-wide radar mapping of ice flow.


I am very busy, but if I have a chance I will try to take a closer look at the pdf.

Your previous comment:
That is significant and rapid warming, but not totally unexpected at high latitudes where greenhouse warming is proceeding at significantly higher rates then is being seen at lower latitudes.


Yes, but this is what has really got me "hand wringing"!
(My apologies for posting a link that is totally OT for an Antarctica thread!)

http://ocean.dmi.dk/arctic/meant80n.uk.php
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Re: Antarctica 2018

Unread postby Plantagenet » Thu 22 Feb 2018, 22:23:39

rockdoc123 wrote:The increased snowfall as measured by the cores in QML is used to update the ensemble of computer models that predict snowfall across the entirety of Antarctica.....


Of course. But extrapolating data from one area across an entire continent isn't ideal, because there is a lot of regional and local variability across the continent. Some areas will have MORE snowfall then QML and some will have less. Relying on data from one site to approximate a huge area is intrinsically inaccurate.

It would be much better to actually have weather stations and ice cores and snow data from all across the continent, but they don't have it so they extrapolate from the limited data they have.

Get it now? Cheers!

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Re: Antarctica 2018

Unread postby Plantagenet » Thu 22 Feb 2018, 22:39:59

chilyb wrote:Hi Plantagenet.... this is what has really got me "hand wringing"!
(My apologies for posting a link that is totally OT for an Antarctica thread!)

http://ocean.dmi.dk/arctic/meant80n.uk.php


WOW!

Thats really impressive---High latitude Arctic temps consistently running ca. 15° above average. I hadn't seen that one.

I live in central Alaska, and even here we're running about 5-10°C above normal this winer. Its been a very unusual and very warm winter so far.

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Re: Antarctica 2018

Unread postby rockdoc123 » Thu 22 Feb 2018, 23:30:35

Of course. But extrapolating data from one area across an entire continent isn't ideal, because there is a lot of regional and local variability across the continent. Some areas will have MORE snowfall then QML and some will have less. Relying on data from one site to approximate a huge area is intrinsically inaccurate.


good lord, they don't 'extrapolate' it to other stations, it is the rate of increase that is measured that is now believed to be a rate of increase in snowfall linked to the increase in warming that is incorporated into the climate model. The climate model uses gridded climate assumptions based on various inputs, one of those assumptions is the amount of precipitation that will result from a certain amount of warming, that isn't the same everywhere on the continent. The Garndner et al paper does the exact same thing as they use a rate of assumed snowfall increase with warming in the RACMO model that allowed for the SMB number they use in their calculations. It is exactly the same damn reasoning. It is pretty clear you do not understand anything about what is being done in either paper.

But here it's OK to reference the climate models? Medley et al., states the models are not accurate in the title of their paper! "Temperature and Snowfall in Western Queen Maud Land Increasing Faster Than Climate Model Projections."

Maybe none of the models are accurate!


Apparently you are obtuse. The Medley paper does not claim the models themselves are incorrect what they point out is the assumption regarding snowfall increase due to warming is what is not consistent with observations and hence should be updated, which they do in their ensemble approach.

Yes, I get that it is cold in Antarctica. But Medley stated the observed rate of change is both "significant and rapid," correct? Why would they choose the word "significant" if it is still really cold?


Well maybe English is a second language for you? Significant means that it is noteworthy and nothing more. Perhaps noteworthy inasmuch as most of Antarctica is actually cooling slightly or relatively stable with respect to temperature. The current temperature at that station is at the warmest it gets all year, around -10 C for the day. The station is only active for 3 months of the year given the temperatures are two cold for the rest of the time (-30 on average through August). If it warms by 1 degree there isn’t going to be a lot of increased melting but there will be increased precipitation according to all of the models.
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Re: Antarctica 2018

Unread postby chilyb » Fri 23 Feb 2018, 07:56:50

rockdoc123,

Apparently you are obtuse.


Well maybe English is a second language for you?


LOL!

I am eagerly awaiting an insult for my third question, which you chose not to answer:

Yes, totally agree. Given there is no rapid retreat of the marine ice sheets that are grounded hundreds of feet below sea level, as we discussed on a previous occasion. Do you agree with that in principle?
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Re: Antarctica 2018

Unread postby jawagord » Sat 03 Mar 2018, 23:18:54

You might think it would be difficult to miss one and a half million penguins. However, after living in obscurity on the Danger Islands off the Antarctic peninsula, a “supercolony” of Adelie penguins has been discovered by scientists.

“Not only do the Danger Islands hold the largest population of Adelie penguins on the Antarctic peninsula, they also appear to have not suffered the population declines found along the western side of Antarctic peninsula that are associated with recent climate change,” said Professor Michael Polito, from Louisiana State University, who co-authored the study.

http://nationalpost.com/news/world/isol ... ments-area

Begs the question are other known penguin populations suffering from climate change or from their exposure to humanity?
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