What’s Behind the Surprising Growth of an Antarctic Ice Sheet?

What’s Behind the Surprising Growth of an Antarctic Ice Sheet?

We often hear about polar ice melting due to global warming, but an Antarctic ice shelf has grown in size in the past 20 years, according to new research.

Scientists say changing winds and sea ice have driven the eastern Antarctic Peninsula ice sheet to expand since the turn of the 21st century. This followed two decades of ice retreat.

Growing Antarctic Ice

A team of researchers from the universities of Cambridge and Newcastle in the UK and the University of Canterbury in New Zealand found that eastern Antarctic Peninsula floating ice shelves increased between 2000 and 2019.

They used satellite measurements dating back 60 years, as well as ocean and atmospheric records to get a detailed understanding of the ice conditions on this 1,400 kilometer long peninsula. Their results showed that 85% of the sea ice in this area has expanded since the early 2000s.

Ice shelves are floating sections of ice that are attached to terrestrial ice caps. They help protect inland ice from erosion and breaking into the ocean.

During their 2019 Antarctica expedition, the researchers noted that “parts of the sea ice coastline were at their most advanced position since satellite records began in the early 1960s,” says the chief scientist of expedition and co-author of the study, Professor Julian Dowdeswell.

The expansion follows rapid ice melt in the second half of the 20th century, including the collapse of Larsen A and B ice shelves in 1995 and 2002. This contributed to the increase global sea levels and flood warnings in coastal areas.

Global sea level has risen by about 21 to 24 centimeters since 1880, about a third of that in the past 25 years. Rising waters threaten infrastructure, homes and livelihoods across coastlines around the world – eight of the world’s 10 largest cities are close to a coast, according to the UN.

What caused the sea ice to grow?

The results, which were published in Nature Geoscience logsuggest that sea ice and regional winds played a vital role in stabilizing the sea ice.

A change in wind conditions over the Weddell Sea pushed floating sea ice against the ice shelves, binding them together.

Prior to 2002, winds in the same area pushed sea ice away from the coast, eroding what scientists call a “buttress effect.” This meant that the ice shelves were exposed to ocean waves and currents, leading to the formation – or calving – of icebergs that broke away into the sea.

“We found that changing sea ice can either protect or trigger the calving of icebergs from the great Antarctic ice shelves,” says lead author Dr Frazer Christie of the Scott Polar Research Institute in Cambridge. of the item.

“Regardless of how the sea ice around Antarctica changes in a warming climate, our observations highlight the often-overlooked importance of sea ice variability to the health of the Antarctic ice sheet. ‘Antarctic.”

An uncertain future for polar ice

The expansion of ice in Antarctica is unusual for the 21st century, when there has been a clear pattern of ice melting.

Antarctic ice loss nearly quadrupled from 51 billion tonnes a year to 199 billion between 1992 and 2016. But scientists aren’t sure how Antarctic ice will be affected by climate change and influence sea levels. in the years to come.

Some models have predicted that overall sea ice in the Southern Ocean will be lost, but others predict sea ice gain.

The authors of this latest research claim that 2020 could have marked the end of expansion in East Antarctica. Over the past 18 months, the number of icebergs breaking off the peninsula has increased.

“It is entirely possible that we are seeing a transition to atmospheric patterns similar to those seen during the 1990s that encouraged sea ice loss and ultimately more sea ice calving,” says the co. -author, Dr. Wolfgang Rack of the University of Canterbury.

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