Pine Island Glacier  (Source: Fotopedia)

Pine Island Glacier through the years  (Source: MSN)
Scientists record measurements beneath Pine Island Glacier

new study by scientists from the British Antarctic Survey (BAS), the National Oceanography Center and Lamont-Doherty Earth Observatory (LDEO) found that the melting of Antarctica's Pine Island Glacier is a large contributor to sea level rise globally. 

The scientists and authors of the study, one of which was Dr. Adrian Jenkins of the British Antarctic Survey, submitted their research to the journal Nature Geoscience. The study was "part of a series of investigations to better understand the impact of melting ice on sea level" showing that sea ice melt such as the North Pole ice cap is not contributing to sea level rise, but the Pine Island Glacier in Antarctica is. 

These researchers used an Autosub, which is an autonomous underwater vehicle, to dive and travel beneath Pine Island Glacier's floating ice shelf. During this endeavor, they were able to record ocean and sea-floor measurements, which revealed two things: Thinning ice in West Antarctica is contributing approximately 10 percent of global sea rise, and there is a 300m high ridge, or mountain, on the sea floor. 

"The discovery of the ridge has raised new questions about whether the current loss of ice from Pine Island Glacier is caused by recent climate change or is a continuation of a longer-term process that began then the glacier disconnected from the ridge," said Jenkins.

At one time, Pine Island Glacier was grounded on top of the ridge, slowing its flow to the sea. More recently, the glacier has thinned and disconnected from the ridge ultimately allowing the glacier to "move ice more rapidly from the land into the sea." This also allowed the deep, warm water in the ocean to "flow over the ridge and into a widening cavity that now extends to an area of 1,000 km² under the ice shelf." 

"Since our first measurements in the the Amundsen Sea, estimates of Antarctica's recent contributions to sea level rise have changed from near-zero to significant and increasing," said co-author Stan Jacobs. "Now finding that the Pine Island Glacier's grounding line has recently retreated more than 30 km from a shallow ridge into deeper water, where it is pursued by a warming ocean, only adds to our concern that this region is indeed the 'weak and underbelly' of the West Antarctic Ice Sheet."

In addition, the increased melting seems to be the primary cause of "persistent ocean freshening" as well as other local and downstream impacts. Jenkins added that research on the Pine Island Glacier is fairly recent, starting in the 1990's, and that there are plenty of questions left to be answered.

"We do not know what kick-started the initial retreat from the ridge, but we do not know that it started some time prior to 1970," said Jenkins. "Since detailed observations of Pine Island Glacier only began in the 1990's, we now need to use other techniques such as ice core analysis and computer modeling to look much further into the glacier's history in order to understand if what we see now is part of a long term trend of ice sheet contraction.

"This work is vital for evaluating the risk of potential wide-spread collapse of West Antarctic glaciers."

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