Sea ice may control stability of Antarctic ice sheet, new research finds

Sea ice may control stability of Antarctic ice sheet, new research finds

Young (blue) and adjacent (smooth white) sea ice off the coast of New Bedford Bay, East Antarctic Peninsula, as depicted by the Operational Land Imager aboard USGS / NASA Landsat 8 on March 5, 2017. Credit: Frazer Christie

Despite the rapid melting of ice in many parts of Antarctica in the second half of the 20syou century, researchers have found that the floating ice shelves that surround the eastern part of the Antarctic Peninsula have made sustained progress over the past 20 years.

Ice shelves – floating sections of ice that are attached to land-based ice sheets – serve as a vital goal to protect against the uncontrolled release of inland ice into the ocean. At the end of 20you century, high levels of warming in the eastern Antarctic Peninsula led to the catastrophic collapse of the Larsen A and B ice shelves in 1995 and 2002, respectively. These events led to the acceleration of ice to the ocean, ultimately accelerating the Antarctic Peninsula’s contribution to sea ‚Äč‚Äčlevel rise.

The jury is now aware of exactly how the sea ice around Antarctica will develop in response to climate changeand therefore affect sea level rise, with some models predicting total loss of sea ice in the Southern Ocean, while others predict an increase in sea ice.

Now an international team of researchers from the Universities of Cambridge and Newcastle in the United Kingdom and the University of Canterbury in New Zealand have used a combination of historical satellite measurements, along with ocean and atmospheric records, to gain the most detailed understanding of how ice conditions change. along the 1,400-kilometer east Antarctic Peninsula.

Sea ice may control stability of Antarctic ice sheet, new research finds

A new study led by the University of Cambridge found that the ice cover in the eastern part of the Antarctic Peninsula has grown in area over the past 20 years due to changing patterns of wind and sea ice. It is not known exactly how sea ice around Antarctica will continue to develop in response to climate change or the effects it will have on the ice sheet of the eastern Antarctic Peninsula. Credit: Fraser Christie

They found that 85% of the perimeter of the ice shelf in this part of Antarctica has advanced since the early 2000s, in contrast to the extensive retreat of the previous two decades. Progress has been associated with changes in atmospheric circulation on a decade-long scale, which has led to more sea ice being carried ashore by the wind.

The results are published in the journal Science of naturesuggest that sea ice plays an important role in stabilizing ice shelves, similar to ice shelves themselves, which stabilize and maintain ice sheets.

“We have found that changing sea ice can either prevent or trigger the emergence of icebergs from the great ice shelves of Antarctica,” he said. Fraser Christie of the Cambridge Institute for Polar Research (SPRI), lead author. “Regardless of how sea ice around Antarctica changes in a warming climate, our observations underscore the often overlooked importance of sea ice variability for the health of the Antarctic ice sheet.

In 2019, Christie and her co-authors were part of an SPRI-led expedition to explore the icy conditions of the Wedel Sea off the coast of East Antarctica, a difficult-to-reach part of the Southern Ocean due to its dense and year-round presence. of sea ice.

Sea ice may control stability of Antarctic ice sheet, new research finds

Schematic diagrams showing the key processes of atmospheric and sea ice, controlling the (in) stability of the ice shelves of the East Antarctic Peninsula over time. After a period of retreat in the 1980s and 1990s, ice shelves have made steady progress over the past two decades. Credit: Fraser Christie

“During the expedition, we noted that parts of the coastline of the ice shelf are in the most advanced position since satellite recordings began in the early 1960s,” said the expedition’s chief scientist and co-author, Professor Julian. Daudeswell, also from SPRI.

After the expedition the team used satellite images going back 60 years, as well as the most modern models of the ocean and atmosphere, to study in detail the spatial and temporal model of change on the ice shelf.

So what caused the advancement of the ice shelves? In the absence of global and ocean warming over the past 20 years, the dominant control has been found to be a change in regional wind patterns over the Wedel Sea, which serves to push sea ice toward ice shelves.

Between 1985 and 2002, by contrast, wind conditions in the same area forced sea ice to move away from the shore. By removing the strengthening effect of sea ice and exposing ice shelves to damaging ocean waves, the pressure on the ice shelves increases, which eventually leads to the melting of icebergs.

Sea ice may control stability of Antarctic ice sheet, new research finds

Water and towels in the Wedel Sea. The image shows a variety of sea ice types, ranging from relatively young Nilas (blue / green; ~ 10 cm thick) to perennial ice (white; ~ 1-2.5 m thick or more). The image obtained from the Operational Land Imager instrument aboard NASA / USGS Landsat 8 on October 21, 2018 and edited by Dr. Fraser Christie, Scott Polar Research Institute. Credit: Dr. Fraser Christie

In almost all cases during the satellite era, calving from the eastern Antarctic Peninsula ice shelves occurs only during or shortly after the removal of sea ice in some form.

However, it is possible that this period of advancing ice will end. Since 2020, there has been a significant increase in the number of icebergs that break away from the eastern part of the Antarctic Peninsula. “It is quite possible to see a transition back to atmospheric models similar to those observed in the 1990s, which encouraged the loss of sea ice and ultimately more thawing of the ice shelf,” said co-author Dr. Wolfgang Rak of the University of Canterbury.

The work was made possible by free open access to the historical satellite image from space agencies and partners, including NASA and the joint Copernicus European Space Agency program.

The study suggests that the ice shelves of Larsen A and B collapsed due to atmospheric rivers

More information:
Frazer DW Christie et al., Advances on the Antarctic ice shelf driven by anomalous atmospheric and sea ice circulation, Science of nature (2022). DOI: 10.1038 / s41561-022-00938-x

Quote: Sea ice can control the stability of the Antarctic ice sheet, new research (2022, May 13), extracted on May 13, 2022 from sheet-stability.html

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