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Antarctica 2018

Re: Antarctica 2018

Unread postby jawagord » Tue 13 Mar 2018, 09:41:24

Another Antarctic summer, another scientists stranded by sea ice story.

The Laurence M. Gould research vessel, seen in a file image, was unable to reach a team of U.S. researchers stuck on an ice-bound island off Antarctica's coast, the National Science Foundation said, March 10, 2018.

Argentina sent the icebreaker ship after receiving a request for assistance on Friday, the country’s foreign ministry said Saturday. The Argentine ship has helicopters able to reach the group’s camp “regardless of the ice conditions,” the National Science Foundation, a U.S. government agency, said.

https://www.yahoo.com/gma/american-scie ... ories.html
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Re: Antarctica 2018

Unread postby Plantagenet » Tue 13 Mar 2018, 13:01:08

I'm scheduled to be in that area about a year from now. I hope they get things sorted out by then. 8)
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Re: Antarctica 2018

Unread postby dohboi » Mon 19 Mar 2018, 22:36:32

More evidence that ice mass loss from Antarctica is accelerating:

Schröder, L., Horwath, M., Dietrich, R., and Helm, V.: Four decades of surface elevation change of the Antarctic Ice Sheet from multi-mission satellite altimetry, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-49, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-49/

Abstract. We developed an approach for a multi-mission satellite altimetry analysis over the Antarctic Ice Sheet which comprises Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat and CryoSat-2. In a first step we apply a consistent reprocessing of the radar alitmetry data which improves the measurement precision by up to 50 %. We then perform a joint repeat altimetry analysis of all missions. We estimate inter-mission offsets by approaches adapted to the temporal overlap or non-overlap and to the similarity or dissimilarity of involved altimetry techniques. Hence, we obtain monthly grids forming a combined surface elevation change time series. Owing to the early missions Seasat and Geosat, the time series span almost four decades from 07/1978 to 12/2017 over 25 % of the ice sheet area (coastal regions of East Antarctica and the Antarctic Peninsula). Since the launch of ERS-1 79 % of the ice sheet area is covered by observations. Over this area, we obtain a negative volume trend of −34 ± 5 km3 yr−1 for the more than 25-year period (04/1992–12/2017). These volume losses have significantly accelerated to a rate of −170 ± 11 km3 yr−1 for 2010–2017. Interannual variations significantly impact decadal volume rates which highlights the importance of the long-term time series. Our time series show a high coincidence with modeled cumulated precipitation anomalies and with satellite gravimetry. This supports the interpretation with respect to snowfall anomalies or dynamic thinning. Moreover, the correlation with cumulated precipitation anomalies back to the Seasat and Geosat periods highlights that the inter-mission offsets were successfully corrected and that the early missions add valuable information.
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Re: Antarctica 2018

Unread postby Plantagenet » Tue 20 Mar 2018, 17:59:08

dohboi wrote:More evidence that ice mass loss from Antarctica is accelerating:

Schröder, L., Horwath, M., Dietrich, R., and Helm, V.: Four decades of surface elevation change of the Antarctic Ice Sheet from multi-mission satellite altimetry, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-49, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-49/

Abstract. We developed an approach for a multi-mission satellite altimetry analysis over the Antarctic Ice Sheet which comprises Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat and CryoSat-2. In a first step we apply a consistent reprocessing of the radar alitmetry data which improves the measurement precision by up to 50 %. We then perform a joint repeat altimetry analysis of all missions. We estimate inter-mission offsets by approaches adapted to the temporal overlap or non-overlap and to the similarity or dissimilarity of involved altimetry techniques. Hence, we obtain monthly grids forming a combined surface elevation change time series. Owing to the early missions Seasat and Geosat, the time series span almost four decades from 07/1978 to 12/2017 over 25 % of the ice sheet area (coastal regions of East Antarctica and the Antarctic Peninsula). Since the launch of ERS-1 79 % of the ice sheet area is covered by observations. Over this area, we obtain a negative volume trend of −34 ± 5 km3 yr−1 for the more than 25-year period (04/1992–12/2017). These volume losses have significantly accelerated to a rate of −170 ± 11 km3 yr−1 for 2010–2017. Interannual variations significantly impact decadal volume rates which highlights the importance of the long-term time series. Our time series show a high coincidence with modeled cumulated precipitation anomalies and with satellite gravimetry. This supports the interpretation with respect to snowfall anomalies or dynamic thinning. Moreover, the correlation with cumulated precipitation anomalies back to the Seasat and Geosat periods highlights that the inter-mission offsets were successfully corrected and that the early missions add valuable information.


Thanks for posting this, Doh.

The use of laser altimetry to measure glacier surface height as a proxy for glacier mass balance was first developed right up here in Alaska by a friend of mine, Prof. Keith Echelmeyer. Keith was a glaciologist and one of the greatest scientists its been my pleasure to meet here in Alaska. Keith came up with the idea of doing laser altimetry surveys of Alaska mountain glaciers, flying over a hundred dangerous traverses in bad conditions over mountain glaciers in Alaska in his own personal plane which he had mounted with a laser altimetry instrument he had devised. Keith's data showed that almost all Alaska glaciers are rapidly thinning.

Keith died about 8 years ago, but its great to see that the method he invented is now being utilized from plane-based platforms and satellite based platforms in Alaska, Antarctica and other areas around the world, and giving much the same results----a warming world is causing mountain glaciers and high latitude ice sheets in Antarctica and elsewhere to thin and shrink and sea level to rise just about everywhere.

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Re: Antarctica 2018

Unread postby jedrider » Tue 20 Mar 2018, 19:21:12

Key Antarctic ice shelf larger than scientists thought
http://www.antarctica.gov.au/news/2018/key-antarctic-ice-shelf-larger-than-scientists-thought

Is this good news or bad news?? Maybe, neutral :)

More ice can NEVER be bad news in our situation, I think.

However, on the other hand, sea level will rise quicker, maybe?
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Re: Antarctica 2018

Unread postby chilyb » Mon 02 Apr 2018, 15:56:18

good day all,

https://www.nature.com/articles/s41561-018-0082-z

Abstract

Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surrounding ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. Here, we combine satellite altimeter observations of ice-elevation change and measurements of ice geometry to track grounding-line movement around the entire continent, tripling the coverage of previous surveys. Between 2010 and 2016, 22%, 3% and 10% of surveyed grounding lines in West Antarctica, East Antarctica and at the Antarctic Peninsula retreated at rates faster than 25 m yr−1 (the typical pace since the Last Glacial Maximum) and the continent has lost 1,463 km2 ± 791 km2 of grounded-ice area. Although by far the fastest rates of retreat occurred in the Amundsen Sea sector, we show that the Pine Island Glacier grounding line has stabilized, probably as a consequence of abated ocean forcing. On average, Antarctica’s fast-flowing ice streams retreat by 110 metres per metre of ice thinning.
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Re: Antarctica 2018

Unread postby chilyb » Mon 02 Apr 2018, 16:07:52

quotes from the author of the nature geoscience paper (Konrad, et al.)

https://phys.org/news/2018-04-antarctic ... floor.html

Dr Konrad said: "Our study provides clear evidence that retreat is happening across the ice sheet due to ocean melting at its base, and not just at the few spots that have been mapped before now. This retreat has had a huge impact on inland glaciers, because releasing them from the sea bed removes friction, causing them to speed up and contribute to global sea level rise."

The researchers also found some unexpected behaviour. Although retreat of the Thwaites Glacier grounding line in West Antarctica has sped up, at the neighbouring Pine Island Glacier - until recently one of the fastest retreating on the continent - it has halted. This suggests that the ocean melting at its base may have paused.

Dr Konrad added: "These differences emphasise the complex nature of ice sheet instability across the continent, and being able to detect them helps us to pinpoint areas that deserve further investigation."


Study co-author Professor Andy Shepherd, from the School of Earth and Environment at Leeds, said: "We were delighted at how well CryoSat-2 is able to detect the motion of Antarctica's grounding lines. They are impossible places to access from below, and usually invisible on the ground, so it's a fantastic illustration of the value of satellite measurements for identifying and understanding environmental change."
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Re: Antarctica 2018

Unread postby dohboi » Sun 08 Apr 2018, 22:10:55

Thanks for those, chil.

Here is a science journalists coverage of the same:

http://www.truth-out.org/news/item/4406 ... -come-true

As Antarctic Melting Accelerates, Worst-Case Scenarios May Come True

...underwater melting of Antarctic glaciers is now occurring at a rate that is doubling every 20 years. This means that melting in the ice continent of Antarctica could soon outpace that occurring across Greenland, which would make Antarctica the single largest source of sea level rise...

...The current worst-case scenario outlined by the Intergovernmental Panel on Climate Change (IPCC) is just over 1.5 meters (4.9 feet) of sea level rise by 2100.

The new data, however, confirms a study from nearly five years ago, in which 90 sea level rise experts were surveyed and confirmed that sea level rise this century will exceed IPCC projections...

...the US National Oceanic and Atmospheric Administration's worst-case scenario is 2.5 meters (8.5 feet) by the same year. This worst-case scenario does not factor in the new data from the recent Antarctica study.

...Sea level rise projections of more than three meters are currently being openly discussed...

...rising seas could result in two billion refugees by 2100...based on the current, lower sea level rise projections
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Re: Antarctica 2018

Unread postby Plantagenet » Sun 08 Apr 2018, 23:39:25

dohboi wrote:http://www.truth-out.org/news/item/4406 ... -come-true

As Antarctic Melting Accelerates, Worst-Case Scenarios May Come True
...rising seas could result in two billion refugees by 2100...based on the current, lower sea level rise projections


I wonder how many people will be displaced by the actual amount of sea level rise we're going to see, which will significantly exceed the IPCC, NOAA, and other scenarios.

Not that it matters all that much. The global warming and sea level rise is locked in.....all that remains is to get the popcorn ready and watch how it all plays out. It should be quite a show.....

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Re: Antarctica 2018

Unread postby dohboi » Wed 02 May 2018, 15:20:29

‘Foehn winds’ causing Antarctica’s Larsen C ice shelf to melt in winter

https://www.carbonbrief.org/foehn-winds ... -in-winter

Parts of Antarctica’s Larsen C ice shelf are melting in the depths of winter, when temperatures typically stay well below freezing, research finds.

Between 2015 and 2017, around 23% of the annual surface melt across the ice shelf occured in the winter months, according to results taken from field and satellite observations...
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Re: Antarctica 2018

Unread postby dohboi » Wed 13 Jun 2018, 18:57:32

Antarctica’s Ice Sheet Is Melting Three Times Faster Than We Thought

https://www.thedailybeast.com/antarctic ... we-thought

Antarctica’s ice sheet is melting three times faster than previously forecasted, according to a report published Wednesday in the journal Nature by 80 scientists. The team said that the ice sheet is melting so fast that 219 billion tons of ice is pouring into the ocean annually—enough to raise sea levels by a half millimeter per year.

Between 1992 and 1997, Antarctica was losing 49 billion tons of ice per year; from 2012 to 2017, that number increased more than eightfold, according to the Ice Sheet Mass Balance Inter-comparison Exercise. At this rate of acceleration, scientists warn that oceans would rise faster than ever, which means a reduced amount of time for low-lying communities to prepare adequately.

“We’re still talking about roughly a half a millimeter per year,” one scientist told The Washington Post. “That isn’t going to sound horribly unmanageable. But remember for the northern hemisphere, for North America, the fact that the location in West Antarctica is where the action is amplifies that rate of sea level rise by up to an about additional 25 percent in a city like Boston or New York.”


Antarctic ice loss has tripled in a decade. If that continues we are in serious trouble.


https://www.washingtonpost.com/news/ene ... s-trouble/
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Re: Antarctica 2018

Unread postby dissident » Wed 13 Jun 2018, 19:39:35

So much for 50 cm sea level rise by 2100.

It is now clear that the trajectory is biased towards the worst case scenario. So the estimate of 7 meters by 2100 by Hansen et al. is looking more and more likely. We are going to be experiencing a global sea level rise cataclysm by 2050.
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Re: Antarctica 2018

Unread postby jawagord » Thu 14 Jun 2018, 07:39:57

dissident wrote:So much for 50 cm sea level rise by 2100.

It is now clear that the trajectory is biased towards the worst case scenario. So the estimate of 7 meters by 2100 by Hansen et al. is looking more and more likely. We are going to be experiencing a global sea level rise cataclysm by 2050.


Is this some kind of new math? .5mm per year x100 years = 50mm = 5cm = 2 inches of sea level rise in 100 years. Greenland melt is contributing more to sea level rise than this!
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Re: Antarctica 2018

Unread postby kiwichick » Thu 14 Jun 2018, 07:49:04

@ Jawagord.....do you have trouble with reading the English language?
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Re: Antarctica 2018

Unread postby dohboi » Thu 14 Jun 2018, 11:07:54

(I do get that impression, k)
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Re: Antarctica 2018

Unread postby rockdoc123 » Thu 14 Jun 2018, 18:07:30

So unlike those here who seem to like to rely on press releases I went and read the paper. I also went through all the supplemental information and downloaded their data sheets.
The paper in question is Shepherd, A. et al, 2018. Mass balance of the Antarctic Ice Sheet from 1992 to 2017. Nature, V 558. https://doi.org/10.1038/s41586-018-0179-y

some observations

How confident is one in saying there is an acceleration in loss of SMB in Antarctica? From a statistical standpoint not at all. If you conduct a T-test on the interval from 2007-2012 (ie. -160 +/- 50 GT/yr) and 2012 – 2017 (-217 +/- 43 GT/yr) the results suggest at the 1 sigma level the probability of the two being statistically different is 0.01%. So although the numbers at first glance seem important statistically you cannot support an argument for an accelerated decrease in SMB from this dataset. This is simply because the errors are so high which is (as I have pointed out on numerous occasion on this threads predecessors) a consequence of large uncertainties around GIA models. This was pointed out in the IMBIE team paper as well as in previous papers (eg. Talpe, M.J. et al, 2017. Ice mass change in Greenland and Antarctica between 1993 and 2013 from satellite gravity measurements. Jour Geod, DOI 10.1007/s00190-017-1025-y). Interestingly enough the Peninsula which is an area where everyone has been wringing their collective hands over the past few years has had little overall impact and in fact, has decreased in the rate of SMB decrease since 2015.

The press releases seem to make a big deal about increased rates of decreased SMB across Antarctica. The data behind the paper’s calculations does not support that view. For the entirety of the WAIS there is a steady increase in SMB drop during the period 2008 through to early 2015 but then there is a rapid rise meaning the rate of contribution to sea level has decreased in the latest period signifying it is not a simple acceleration story. In more detail when you look at regions EAIS is increasing throughout much of the period during which AIS overall is dropping with a period from late 2012 to early 2015 where it decreases before again increasing. What is evident when you look at the three regions (WAIS, EAIS and the ANT Peninsula) what is happening in the WAIS overwhelms everything else.

So why is WAIS showing a significant increase in the rate of drop in SMB between 2006 and 2015? The temperature trend from either satellite or surface stations such as Scott and McMurdo do not show an increase in surface air temperatures during this period. The southern ocean SST was also decreasing during this period. Perhaps upwelling increased but something that should be considered is the contribution to basal melt from high heat flow in the region. Recent work seems to point to areas of high heat flux at the rock/ice interface over large parts of West Antarctica west of the suture zone. (eg. Martos, Y, et al, 2017. Heat Flux Distribution of Antarctica Unveiled. Geoph Res Lett, 44. doi.org/10.1002/2017GL075609)

But the bottom line here is how much should one be worried? Most papers seem to agree that the period from up to 2012 was an average of somewhere between -60 and -120 GT/yr or 0.17 mm/yr to 0.33 mm/yr sea level rise equivalent. In the recent IMBIE team paper they suggested a rate from 2012 – 2017 of -219 GT/yr which his 0.6 mm/yr sea level rise equivalent. If that rate persisted to 2100 that is a rise of sea level of 49 mm or 4.9 cm or 1.9 inches for the non-metric folks. The rest of the world contribution would have to seriously step up to make up the difference to get 1 m of sea level rise by 2100 let alone the ludicrous suggestion of 7 m. Even if you try to argue that the last two years of data in the IMBIE paper which shows a decrease in the rate of SMB decrease and that the noted average increase in the rate of SMB decrease from 2012 to 2014 continued onwards to 2100 you are looking at a total sea level equivalent contribution of 137 mm (13 cm) or 5 inches. If you are worried about this then you need a better hobby IMO.
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Re: Antarctica 2018

Unread postby onlooker » Fri 15 Jun 2018, 01:08:57

https://www.commondreams.org/news/2018/ ... ialnetwork

Utterly Terrifying': Study Affirms Feedback Loop Fears as Surging Antarctica Ice Loss Tripled in Last Five Years
"The most robust study of the ice mass balance of Antarctica to date," scientists say, "now puts Antarctica in the frame as one of the largest contributors to sea-level rise
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Re: Antarctica 2018

Unread postby onlooker » Fri 15 Jun 2018, 01:31:04

https://www.nytimes.com/2018/06/13/clim ... aster.html
Antarctica Is Melting Three Times as Fast as a Decade Ago
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Re: Antarctica 2018

Unread postby kiwichick » Fri 15 Jun 2018, 02:46:06

seems rocdoc123 also has trouble assimilating what tripling in 5 years means

Hansen's 5 metres by 2100 only assumed Doubling every decade
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Re: Antarctica 2018

Unread postby rockdoc123 » Fri 15 Jun 2018, 10:39:43

seems rocdoc123 also has trouble assimilating what tripling in 5 years means

Hansen's 5 metres by 2100 only assumed Doubling every decade


Apparently, both you and onlooker haven't read the paper ....did you? Perhaps you should do that.

And if you have specific arguments with my comments then you should actually point them out rather than posting another press release that actually misinterprets what the significance of the results are.

Perhaps you do not have any background in statistical analysis...as I said from the standpoint of statistical analysis there is no difference in the trend reported from 2007 - 2012 and the trend from 2012 - 2017. In short, there is no acceleration statistically speaking.

And as I said at the end, ignoring the statistical argument .....using the rate of accelerated decrease from the data set and ignoring the fact that over the last two years the rates have slowed considerably (or simply put for the brain dead....taking the highest rate of SMB loss recorded) and continuing that as an acceleration of loss from current data results in 13 cm of sea level equivalent rise by 2100. If you can pull apart the math have at it but otherwise, your comments are pretty much irrelevant. For the math challenged such as yourself 13 cm is about 1% of the 7 m someone claimed. If you want to argue this level of sea level rise you need to go someplace else as the data in Antarctica certainly does not support it at this point in time. This is especially true if the actual decrease in loss over the entire continent since 2015 is a meaningful trend. And given Antarctica contributes about 17% of the total sea level rise then that 13 cm contribution becomes 76 cm globally by 2100 if all other areas (Greenland, glaciers, thermal expansion) accelerate contribution at the same rate.
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