“Similar to syrup, warm ice flows more readily than cold ice.” Bryn Hubbard
Larsen C ice shelf is in big trouble which means all of us are in big trouble. A disintegrating ice shelf will not raise sea level by very much. But once the shelf that buttresses the glaciers on the continent is gone, the glacial ice can rapidly enter the ocean, raising sea level. It is that ice which will flood our coastal cities.
There has been catastrophic breakup events at Larsen A ice shelf which collapsed in 1995 and Larsen B ice shelf in 2002. Larsen C, which is larger than New Hampshire and Vermont combined, is next in line to crack up geographically.
A team led by Prof Bryn Hubbard, director of the Centre for Glaciology at Aberystwyth University in Wales, released a research paper describing how a recently discovered river of solid ice under the Larsen C ice shelf could be speeding up the flow of ice to the ocean.
Carbon Brief reports:
The Antarctic Peninsula is one of the fastest warming places on Earth. Temperatures have risen by 2.5C in the past 50 years. Warmer air is causing the surface of the ice to melt, forming pools of water known as “meltponds”.
Meltponds tend to form in a line “like a string of sausages” and are thought to have contributed to the collapse of ice shelves in the past, including Larsen B. Hubbard tells Carbon Brief
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The vast icy layer below Larsen C is a concern, says Hubbard. It is warmer than the compacted snow it replaced because of the latent heat that is released as the percolating meltwater refreezes at depth. This, in turn affects how the ice moves, Hubbard explains:
Hubbard and his team installed a string of instruments to take measurements within the icy layer, returning to collect the data a year later. They found temperatures of between -5C and -10C, a full 10C above what they expected for this depth range.Hubbard suggests that the massive layer of ice is denser than that which would be present in an ice shelf that has no melt ponds. In addition, the ice is much warmer. The density and heat both impact the movement and stability of the Larsen C shelf.
The discovery of a massive ice layer beneath the surface at Cabinet Inlet on the Larsen-C ice shelf, Antarctic Peninsula.From the 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.