The Pine Island Glacier has been identified as a major contributor to Earth’s sea level rise.
New results from an investigation by scientists from the British Antarctic Survey, Lamont-Doherty Earth Observatory and the National Oceanography Centre published in the journal Nature Geoscience show that West Antarctica is currently contributing nearly 10% of global sea level rise.
One of the major sources of this rise is the Pine Island Glacier, which was the focus of a series of visits by Autosub, an autonomous underwater vehicle that dove several times under the massive glacier to report on the conditions below.
What scientists found is that the Pine Island Glacier is no longer resting atop a mountain ridge which had been minimizing its ice loss. According to the report the last time the glacier had been in contact with the ridge was the early 1970’s.
“A January 1973 Landsat 1 Multi-spectral Scanner picture showed a bump in the ice surface that had disappeared everal years later,” said the authors.
This ridge had first of all slowed its flow into the sea, but in recent years due to the glacier thinning it has moved away from the ridge, allowing the glacier to move ice more rapidly from the land into the sea. This also allowed deep warm water to flow over the ridge and into the ice shelf, which is causing the bottom of the ice shelf to melt which increases the melting and thinning of the glacier.
“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 when the glacier disconnected from the ridge,” Lead author Dr Adrian Jenkins of British Antarctic Survey said.
“We do not know what kick-started the initial retreat from the ridge, but we do know that it started some time prior to 1970,” he continued. “Since detailed observations of Pine Island Glacier only began in the 1990s, we now need to use other techniques such as ice core analysis and computer modelling 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.”
“Since our first measurements in the Amundsen Sea, estimates of Antarctica’s recent contributions to sea level rise have changed from near-zero to significant and increasing,” adds co-author Stan Jacobs. “Now finding that the PIG’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 underbelly’ of the West Antarctic Ice Sheet. Increased melting of continental ice also appears to be the primary cause of persistent ocean freshening and other impacts, both locally and downstream in the Ross Sea.”
Source: British Antarctic Survey