Thursday, 27 October 2016

These Antarctic glaciers have had staggering ice loss in the past 15 years

Few regions of the world are as unstable in the face of advancing climate change as frozen West Antarctica, where rapidly melting glaciers have scientists on edge about the potential for huge amounts of future sea-level rise.
Now, a new study has pinpointed some of the most rapid ice losses observed in the region in the past 15 years - and it supports a growing scientific belief that warm ocean water is behind the melting.

"[The study] seems to provide a strong piece of evidence to support a general hypothesis about what's happening in the Amundsen Sea," said Ala Khazendar, a polar scientist at Nasa's Jet Propulsion Laboratory and the new paper's lead author.

Much of the focus on West Antarctica centres around the Amundsen Sea region, whose glaciers may already be experiencing irreversible ice loss. The glaciers backing up to this sea have the potential to cause about 1.2m of sea-level rise, and the ice contained in West Antarctica as a whole could raise sea levels by 3m.

Several of the region's largest glaciers have inspired some of the greatest concern. Just last week, US and British science agencies announced a joint multimillion-dollar research mission to study the massive Thwaites Glacier, which scientists believe may already be contributing about 10 per cent of all global sea-level rise. And a recent study on the nearby (and slightly smaller) Pine Island Glacier has documented recent rapid retreat .

Now, research increasingly suggests it's not just atmospheric warming that's causing all the problems in West Antarctica, but the influence of the ocean as well . Many glaciers in this region back right up to the edge of the sea, terminating in what's known as an ice shelf - a ledge of floating ice that's disconnected from the bedrock and juts out into the water, helping to stabilise the glacier and hold back the flow of ice behind it.

Scientists now believe that rising water temperatures may be helping to weaken ice shelves by seeping into the cavities beneath them and lapping up against the exposed ice. If an ice shelf thins or breaks, the glacier behind it begins to pour ice into the ocean and retreat inland. The point where the bottom of the glacier actually joins to the bedrock is known as the grounding line, and scientists often use it as a point of reference to measure how far a glacier has retreated over time.

Scientists believe this is what's driving the retreat of the Pine Island and Thwaites glaciers. But while these glaciers hold some of the greatest potential to raise sea-levels, smaller glaciers in the area can also offer some important insights into the processes driving ice loss in the region.

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