We often hear about the melting of polar ice due to global warming, but one Antarctic ice shelf has grown in the past 20 years, a new study finds.
Scientists say changing wind and sea ice patterns have caused the East Antarctic ice sheet to widen since the beginning of the 21st century. This came after two decades of retreating ice.
Antarctic ice growing
A team of researchers from universities Cambridge and Newcastle in the UK and the University of Canterbury in New Zealand found that floating ice shelves on the East Antarctic Peninsula grew between 2000 and 2019.
They used satellite measurements dating back 60 years, as well as ocean and atmospheric records to gain a detailed understanding of ice conditions on the 1,400-kilometre peninsula. Their results showed that 85 percent of the ice shelf in this area has grown since the early 2000s.
Ice shelves are floating sections of ice attached to land ice sheets. They help protect inland ice from erosion and separation in the ocean.
During their 2019 expedition to Antarctica, researchers noted that “parts of the ice shelf coast have been at their most advanced since satellite records began in the early 1960s,” says lead scientist and study co-author Professor Julian Dodswell.
The expansion followed the rapid melting of ice 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 rise global sea levels Flood warnings in coastal areas.
Global sea levels have risen by about 21-24 centimeters since 1880, and nearly a third of that has occurred in the past 25 years. Rising water levels threaten infrastructure, homes and livelihoods Coasts around the world Eight of the world’s ten largest cities are located near the coast, according to the United Nations.
What is the reason for the growth of the ice shelf?
The results were published in the journal Nature Geoscience magazineindicates that sea ice and regional wind patterns had a vital role to play in ice shelf stability.
A change in wind conditions over the Weddell Sea has pushed the sea ice floating on the ice shelves, linking them together.
Prior to 2002, winds in the same area blew sea ice away from the coast, eroding what scientists call a “supporting effect.” This means that the ice shelves were exposed to ocean waves and currents, resulting in the formation – or birth of – icebergs that erupted into the sea.
“We found that changing sea ice can protect against, or initiate the movement of, icebergs from large Antarctic ice shelves,” explains Dr. Fraser Christie of the Scott Polar Research Institute in Cambridge, lead author of the research paper.
“Regardless of how sea ice around Antarctica changes in a warming climate, our observations highlight the often-overlooked importance of sea ice variability on the health of the Antarctic ice sheet.”
An uncertain future for polar ice
Antarctic ice expansion is unusual in the 21st century, when there was a clear pattern of ice melt.
Antarctic ice loss nearly quadrupled from 51 billion tons annually to 199 billion between 1992 and 2016. But scientists don’t know for sure how Antarctic ice will be affected by climate change and affect sea levels in the coming years.
Some models projected that total sea ice in the Southern Ocean would be lost, but others predict an increase in sea ice.
The authors of this latest paper say 2020 could have marked the end of the expansion in East Antarctica. In the past eighteen months there has been an increase in the number of icebergs breaking off from the peninsula.
“It is entirely possible that we are seeing a transition to atmospheric patterns similar to those observed during the 1990s that encouraged sea ice loss and, eventually, more ice shelf,” says co-author Dr Wolfgang Rak from the University of Canterbury.