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Author Topic: Surge of WAIS Ice Mass Loss  (Read 92076 times)

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #200 on: December 13, 2016, 08:40:19 PM »
The linked presentation is entitled: “RAPID RESPONSE OF WEST ANTARCTIC ICE SHELVES TO EL NIÑO AND LA NIÑA”; and it indicates that El Nino events result in accelerated ice mass loss from Amundsen Sea ice shelves:

https://scripps.ucsd.edu/news/scripps-news-2016-agu-fall-meeting

El Niño’s Immediate Effects on Antarctica’s Ice Shelves

C14A-05 • Monday, Dec. 12, 5 p.m. • Moscone West 3007

Description: "Ice shelves experience rapid changes when the global climate phenomenon known as El Niño occurs.  Researchers at Scripps Institution of Oceanography at the University of California San Diego and Earth and Space Research in Corvallis, Ore. found that El Niño thickens the ice shelves by increasing snowfall on top of them, and thins the ice shelves by increasing melt below them as warm ocean water comes into contact with their bases.

The researchers, led by Scripps postdoctoral researcher Fernando Paolo, analyzed surface-height records made between 1994 and 2012 at the Amundsen Sea ice shelves in West Antarctica. They found that El Niño episodes lead to a net loss in ice-shelf mass because the ice lost at the base is denser than the snow gained at the surface.

The study suggests that if El Niños become more frequent in a future climate, the variability of ice shelves will increase. This has a range of implications for the dynamics of grounded ice in Antarctica, which is a source of large uncertainty in global sea-level rise projections. The study also highlights the importance of the contribution of changing snowfall on ice-shelf mass balance at timescales shorter than a decade, which has been underappreciated until now."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #201 on: December 14, 2016, 05:49:27 PM »
The attached Sentinel1 image of the Thwaites Eastern Ice Shelf & residual Ice Tongue is from Dec 14 2016.  It indicates to me that the residual Ice Tongue is continuing to degrade and at some point we can expect another surge of ice flow from this critical area.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

solartim27

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Re: Surge of WAIS Ice Mass Loss
« Reply #202 on: December 17, 2016, 09:00:52 PM »
Here's a gif of a small calving at the southern end of Thwaites, Dec 3 to 17.

http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20161217T042738_2F36_S_1.final.jpg

S1A_EW_GRDM_1SSH_20161203T044353_2FFE_S_1.final.jpeg
FNORD

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #203 on: January 27, 2017, 11:12:32 PM »
Article on the BBC today:

"The scale and pace of change now taking place in West Antarctica is captured in a new, long-term satellite record.

Scientists have combined nearly a quarter of a century of observations to show how the region's great glaciers are losing height by up to 7m per year.

The satellite data also traces the way this thinning behaviour has spread up the length of the ice streams.

As the glaciers accelerate, they have to take ever more ice from the interior to compensate for the speed-up. This means they thin; they lose height, which we can detect from space," explained Dr Hannes Konrad from the UK's Centre for Polar Observation and Monitoring (CPOM).

"And if there is no increase in snow and ice in the interior then this thinning will just migrate further and further upstream,"

http://www.bbc.com/news/science-environment-38256932

Article here (paywallled):
http://onlinelibrary.wiley.com/doi/10.1002/2016GL070733/full

See also:

Cook, T. (2017), A comparison of surface thinning in West Antarctic glaciers, Eos, 98, doi:10.1029/2017EO066407. Published on 24 January 2017.

https://eos.org/research-spotlights/a-comparison-of-surface-thinning-in-west-antarctic-glaciers?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz012717

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #204 on: February 18, 2017, 10:11:01 PM »
The attached images come from the following linked website regarding ice mass loss rates for Antarctica from August 16 2002 to July 16 2016.  The first three images respectively show ice mass loss from zones AIS22, AIS21 & AIS 20; which are the three zones in the WAIS with the darkest red shading in the fourth image (with AIS22 for the PIG basin) 

https://data1.geo.tu-dresden.de/ais_gmb/
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #205 on: December 26, 2017, 05:49:08 PM »
Hopefully, the University of Washington fleet of robotic drone submersibles will provide new data on the thinning of the Pine Island Ice Shelf next year:

Title: "UW’s robotic fleet will probe under Antarctic ice shelves for clues to future sea-level rise"

http://www.theolympian.com/news/local/article191577664.html

Extract: "The UW team plans to focus on Pine Island Glacier, Antarctica’s fastest-melting ice sheet, where a huge iceberg broke off this fall. The glacier’s flow has sped up nearly 75 percent in the past 40 years, possibly due to thinning of the floating ice shelf.

“That’s worrisome,” Christianson said. “We didn’t suspect these ice sheets would change as fast as they have.”
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

oren

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Re: Surge of WAIS Ice Mass Loss
« Reply #206 on: December 26, 2017, 10:49:39 PM »
Hopefully, the University of Washington fleet of robotic drone submersibles will provide new data on the thinning of the Pine Island Ice Shelf next year:

Title: "UW’s robotic fleet will probe under Antarctic ice shelves for clues to future sea-level rise"

http://www.theolympian.com/news/local/article191577664.html

Extract: "The UW team plans to focus on Pine Island Glacier, Antarctica’s fastest-melting ice sheet, where a huge iceberg broke off this fall. The glacier’s flow has sped up nearly 75 percent in the past 40 years, possibly due to thinning of the floating ice shelf.

“That’s worrisome,” Christianson said. “We didn’t suspect these ice sheets would change as fast as they have.”
Very good.

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #207 on: January 02, 2018, 04:25:41 PM »
The linked open access reference discusses the nature and implications of recent ice mass loss from Crosson and Dotson ice shelves:

Lilien, D. A., Joughin, I., Smith, B., and Shean, D. E.: Elevated melt causes varied response of Crosson and Dotson Ice Shelves in West Antarctica, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-248, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2017-248/
https://www.the-cryosphere-discuss.net/tc-2017-248/tc-2017-248.pdf

Abstract. Crosson and Dotson Ice Shelves are two of the most rapidly changing outlets in West Antarctica, displaying both significant thinning and grounding-line retreat in recent decades. We used remotely sensed datasets to investigate the processes controlling their changes in speed and grounding-line position over the past 20 years. We combined these observations with inverse modeling of the viscosity of the ice shelves to understand how weakening of the shelves affected this speedup. These ice shelves have lost mass continuously since the 1990s, and we find that this loss is primarily a result of melt beneath Dotson. High melt rates persisted over the period covered by our observations (1996–2014), with the highest rates beneath areas that ungrounded during this time. Grounding line flux exceeded basinwide accumulation by about a factor of two throughout the study period, consistent with earlier studies, resulting in significant loss of grounded as well as floating ice. The near doubling of Crosson's speed in some areas during this time likely is the result of weakening of its margins and retreat of its grounding line. This speedup contrasts with Dotson, which has continued to move slowly despite high, increasing melt rates near its grounding line. Our results indicate that changes to melt rates began before 1996, and suggest that observed increases in melt in the 2000s compounded an ongoing retreat of this system. Advection of a channel along Dotson, as well as the grounding-line position of Kohler Glacier, suggest that Dotson experienced a change in flow around the 1970s, which may be the initial cause of its continuing retreat.


Caption: "Figure 1: Overview of study area a) 1996 surface speed overlaid on the mosaic of Antarctica (MOA) (Haran et al., 2013).  Yellow and green lines show grounding line positions in 1996 and 2011 respectively (Rignot et al., 2014). Black lines indicate catchment boundaries of Crosson and Dotson used for flux calculations. b) Surface elevation relative to the EGM2008 geoid from WorldView/GeoEye stereo DEM mosaic (Shean et al., 2016). c) Ice bottom elevation relative to the EGM2008 geoid, which represents bed elevation over grounded ice."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #208 on: January 13, 2018, 07:05:37 PM »
The linked reference discusses the link between bathymetry and relatively recent calving of the PIIS:

Arndt, J. E., Larter, R. D., Friedl, P., Gohl, K., and Höppner, K.: Bathymetric Controls on Calving Processes at Pine Island Glacier, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-262, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2017-262/

Abstract. Pine Island Glacier is the largest current Antarctic contributor to sea level rise. Its ice loss has substantially increased over the last 25 years through thinning, acceleration and grounding line retreat. However, the calving line positions of the stabilizing ice shelf did not show any trend within the observational record (last 70 years) until calving in 2015 led to unprecedented retreat and changed alignment of the calving front. Bathymetric surveying revealed a ridge below the former ice shelf and two shallower highs to the north. Satellite imagery shows that ice contact on the ridge likely was lost in 2006 but was followed by intermittent contact resulting in back stress fluctuations on the ice shelf. Continuing ice shelf flow also led to occasional ice shelf contact with the northern bathymetric highs, which initiated rift formation that led to calving. The observations show that bathymetry is an important factor in initiating calving events.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson