Antarctic Discovery Reveals Larsen C Ice Shelf Weakness

Larsen CResearchers report discovery of a massive subsurface ice layer, at least 16 km across, several kilometres long and tens of metres deep, located in an area of intense melting and intermittent ponding on the Larsen C Ice Shelf in Antarctica which may suggest the ice shelf is even more fragile than thought. This image is from the research paper published in Nature Communications. Cabinet Inlet basemap and surface ponding. Location map of Cabinet Inlet study site on Larsen C Ice Shelf based on MODIS data from 3rd December 2014. (a) Main figure location in Antarctica (red box). (b) Landsat expansion of Cabinet Inlet from 31st December 2001, showing surface ponding (dark patches) and the locations of the borehole (yellow dot) and 200-MHz GPR transects (red lines). Courtesy: authors and Nature Communications.

Researchers report discovery of a massive subsurface ice layer, at least 16 km across, several kilometres long and tens of metres deep, located in an area of intense melting and intermittent ponding on the Larsen C Ice Shelf in Antarctica which may suggest the ice shelf is even more fragile than thought

From Aberystwyth University

An international research team led by academics from Aberystwyth and Swansea Universities has published a significant piece of research that sheds new light on one of our greatest natural phenomena. The formation of ice shelves has often been considered to provide important evidence as to how our climate has and will develop. Until recently however it has been extremely difficult to gather valuable data due to the inhospitable landscapes of the ice shelves themselves.

The team of researchers, made up largely from the Welsh universities, organised a drilling expedition to one of the largest ice shelves in the Antarctica known as Larsen C – a floating ice shelf that is approximately two and a half times the size of Wales. Working with the logistical support of the British Antarctic Survey, they were able to establish a base on the shelf and carry out the work which provides vital information on the response of ice shelves to a warming climate for current and future research.

Professor Bryn Hubbard, Director of the Centre for Glaciology, Department of Geography and Earth Science at Aberystwyth University, explains the difficulties of reaching the ice shelf in the first place.

“These kinds of places are by their nature inhospitable, with sub-zero temperatures and difficult conditions underfoot. As a result, landing aircraft there with our research equipment and support teams is a very tricky business. We were very fortunate to get the co-operation of the British Antarctic Survey Air Unit and Field Guides as their expertise was invaluable in ensuring the success of the project as well as our safety.”

It had always been thought that ice in such structures forms gradually about 50-60 metres down into the ice shelf, but once the Welsh team started drilling they struck the ice at a depth of only three metres. This in itself was an important finding according to Professor Hubbard.

“I think it’s fair to say that we were all surprised when we hit the ice so quickly as it completely contradicted our previous conceptions of how ice forms within the shelf. We believe that climate change has played a role in this due to the particularly strong warming this part of Antarctica in particular has experienced in recent decades.

“However, more important is how this information will help us with our future computer modelling work and understand how such structures will evolve under predicted future climate-change scenarios. It is potentially a ground-breaking discovery for the structure of ice shelves across Antarctica.”

The research team spent over two months on the ice shelf gathering information in temperatures that ranged between -5 to -20 degrees Celsius. In addition to the Aberystwyth and Swansea teams, there was also a north Wales presence as the specialist equipment used to collect high-resolution images from the holes is made by Deganwy-based firm, Robertson Geologging.

The research findings are published  in the respected open access science journal, Nature Communications.

Professor Bryn Hubbard was recently awarded the prestigious Polar Medal, joining an illustrious list of recipients that includes Captain Robert F Scott, Sir Ernest Shackleton and Sir Edmund Hillary.

Abstract

Surface melt ponds form intermittently on several Antarctic ice shelves. Although implicated in ice-shelf break up, the consequences of such ponding for ice formation and ice-shelf structure have not been evaluated. Here we report the discovery of a massive subsurface ice layer, at least 16 km across, several kilometres long and tens of metres deep, located in an area of intense melting and intermittent ponding on Larsen C Ice Shelf, Antarctica. We combine borehole optical televiewer logging and radar measurements with remote sensing and firn modelling to investigate the layer, found to be ~10 °C warmer and ~170 kg m-3 denser than anticipated in the absence of ponding and hitherto used in models of ice-shelf fracture and flow. Surface ponding and ice layers such as the one we report are likely to form on a wider range of Antarctic ice shelves in response to climatic warming in forthcoming decades.

Citation

Bryn Hubbard, Adrian Luckman, David W. Ashmore, Suzanne Bevan, Bernd Kulessa, Peter Kuipers Munneke, Morgane Philippe, Daniela Jansen, Adam Booth, Heidi Sevestre, Jean-Louis Tison, Martin O’Leary and Ian Rutt; Massive subsurface ice formed by refreezing of ice-shelf melt ponds; Nature Communications doi:10.1038/ncomms11897.

Source

Aberystwyth University news release.

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