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Antarctica 2018

Re: Antarctica 2018

Unread postby Plantagenet » Tue 19 Jun 2018, 16:02:00

Neat little youtube movie prepared by a large number of Antarctic scientists shows net changes in surface elevation for Antarctica. The movie was posted to accompany a paper on the mass balance of Antarctica published by the journal NATURE in June 2018. As Antarctica loses mass, there are concomitant changes in glacier morphology.

visualization showing changes in surface elevation of Antarctica

The film shows the location of large drops in elevation of glaciers around the coast of Antarctica, as ice flow accelerates and ice flux to the ocean increases, along with very small increases in the elevation of some interior regions due to increased precipitation.

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Re: Antarctica 2018

Unread postby Plantagenet » Fri 22 Jun 2018, 16:16:53

Land uplift is occurring in West Antarctica faster then anywhere else on earth. As the glacier ice melts, the land is rising in response to the huge decreases in ice loading.

bedrock-west-antarctica-surprisingly-rapid-uplift

Perhaps this can help stabilize the West Antarctic ice Sheet somewhat?? The land there is rising much faster then sea level is rising, so at least the effect of rising sea on WAIS glacier stability will be minimized in some areas.

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Re: Antarctica 2018

Unread postby dohboi » Fri 22 Jun 2018, 19:51:07

Interesting. Thanks for these links and info, P.
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Re: Antarctica 2018

Unread postby rockdoc123 » Sat 23 Jun 2018, 10:44:04

Land uplift is occurring in West Antarctica faster then anywhere else on earth. As the glacier ice melts, the land is rising in response to the huge decreases in ice loading.


the paper this press release refers to is:

Barletta, V.R. et al, 2018. Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability. Science, 22, V 360. Pp 1335-1339

in the paper they discuss the modeling inputs required to replicate the uplift rate and the only solution they arrived at is to have a very low viscosity in the upper mantle. That low viscosity is consistent with high heat flow which I have pointed to a number of times as being present west of the Trans-Antarctic mountain range that marks the tectonic suture zone.

We found that ASE has a rheological structure very different from those commonly used in global and regional dynamic Earth models, with the upper mantle viscosity being about two orders of magnitude lower. Low viscosity provides independent support for a hot mantle, as suggested by seismological results and an elevated geothermal heat flux in the region. Low viscosity is also supported by the characteristics of the subglacial geology that provide important boundary conditions for the evolution of the ice sheet. The low viscosity we found in deeper layers could be an indication of a plume-like thermal structure such as the one hypothesized in nearby Marie Byrd Land


If this is the case there is an argument to be made that melt from West Antarctica and the Peninsula has a strong component of basal melt imposed by high basal heat flow. As ice melts there is an isostatic response and consequent uplift due to the low viscosity mantle.

There is an additional aspect that can be attributed to tectonics here not discussed in the paper. The region in question is characterized by a history of rifting, subduction and uplift that was thought to have ceased millions of years ago. If, as the high heat flow suggests rifting has been reinitiated then the tectonics and associated uplift in the region could also change.
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Re: Antarctica 2018

Unread postby dohboi » Sun 24 Jun 2018, 23:07:51

Satellites track vanishing Antarctic ice

In West Antarctica, ice shelves are being eaten away by warm ocean water, and those in the Amundsen and Bellingshausen seas are up to 18 per cent thinner than in the early 1990s. At the Antarctic Peninsula, where air temperatures have risen sharply, ice shelves have collapsed as their surfaces have melted. Altogether, 34,000 km2 of ice shelf area has been lost since the 1950s.



In the Amundsen Sea, for example, ice shelf thinning of up to six metres per year has triggered a 1.5 km per year acceleration of the Pine Island and Thwaites glaciers. These glaciers have the potential to raise sea levels by more than a metre, and are now widely considered to be unstable.


https://phys.org/news/2018-06-satellite ... c-ice.html
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Re: Antarctica 2018

Unread postby rockdoc123 » Tue 26 Jun 2018, 16:05:53

another recent paper pointing to evidence re: active volcanism below West Antartica

Loose, B., 2018. Evidence of an active volcanic heat source beneath the Pine Island Glacier, Nature Comm, 9,

Tectonic landforms reveal that the West Antarctic Ice Sheet (WAIS) lies atop a major volcanic rift system. However, identifying subglacial volcanism is challenging. Here we show geochemical evidence of a volcanic heat source upstream of the fast-melting Pine Island Ice Shelf, documented by seawater helium isotope ratios at the front of the Ice Shelf cavity. The localization of mantle helium to glacial meltwater reveals that volcanic heat induces melt beneath the grounded glacier and feeds the subglacial hydrological network crossing the grounding line. The observed transport of mantle helium out of the Ice Shelf cavity indicates that volcanic heat is supplied to the grounded glacier at a rate of ~ 2500 ± 1700 MW, which is ca. half as large as the active Grimsvötn volcano on Iceland. Our finding of a substantial volcanic heat source beneath a major WAIS glacier highlights the need to understand subglacial volcanism, its hydrologic interaction with the marine margins, and its potential role in the future stability of the WAIS.


https://www.nature.com/articles/s41467-018-04421-3
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Re: Antarctica 2018

Unread postby Plantagenet » Tue 26 Jun 2018, 16:42:07

Brice Loose, the lead author on this paper, warns against misinterpreting the findings of a volcanic signal from somewhere under the WAIS.

Loose cautions, this does not imply that volcanism is the major source of mass loss from Pine Island. On the contrary, "there are several decades of research documenting the heat from ocean currents is destabilizing Pine Island Glacier, which in turn appears to be related to a change in the climatological winds around Antarctica," Loose said.

Read more at: <https://phys.org/news/2018-06-volcanic-source-major-antarctic-glacier.html#jCp>

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Re: Antarctica 2018

Unread postby rockdoc123 » Tue 26 Jun 2018, 16:57:39

Loose cautions, this does not imply that volcanism is the major source of mass loss from Pine Island. On the contrary, "there are several decades of research documenting the heat from ocean currents is destabilizing Pine Island Glacier, which in turn appears to be related to a change in the climatological winds around Antarctica," Loose said.


extremely misleading. There is no "research documenting the heat from ocean currents", each and every paper reverts to warm waters as a source of melt but there is an absence of mass balance calculations showing how much is actually related to warm waters (ie. it is treated as the default cause and not a bottom-up calculation). The point here is that if there is heat from below that is contributing to melting then the effects of warm ocean waters or high atmospheric temperatures are less than previously thought. Something I have pointed to a number of times on this thread and its predecessors and which is backed up by other recent research.

IF you bothered to read the paper there is a full range of possible outcomes regarding the impact of heat from below, all the way from minimal to very significant which means further attention needs to be paid to high heat flow in West Antarctica. A point they make is if heat flow from the lower source is in excess of 150 mW/m2 then there will be significant contribution to melt and recent other papers have pointed out to large areas in West Antarctica that have heat flow in excess of this level.

Why is this important? The main location of volcanoes and identified high heat flow is in West Antarctica which is also the source of the vast majority of melt, which is certainly a smoking gun. Hence more attention needs to be paid to heating from below, as these authors point out and others have pointed out previously.
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