Intense atmospheric rivers help create huge holes in Antarctic sea ice

Hot, humid rivers of air can affect the entire continent and influence climate change.

Warm, humid rivers of air in Antarctica play a key role in creating huge sea ice holes in the Weddell Sea and can affect ocean conditions across the vast continent and climate change, according to Rutgers research.

Scientists studied the role of long, intense plumes of warm, humid air – known as atmospheric rivers – in creating huge openings in sea ice. They focused on the Weddell Sea region in the Southern Ocean near Antarctica, where these sea ice holes (called polynyas) rarely develop during the winter. A large hole in this area was first observed in 1973, and a hole developed again in late winter and early spring 2017.

In the first study of its kind, published in the journal Advances in science, scientists found that repeated strong atmospheric rivers from late August to mid-September 2017 played a crucial role in the formation of the sea ice hole. These rivers carried warm, humid air from the coast of South America to the polar environment, warming the surface of the sea ice and making it vulnerable to melting.

“Polynyas strongly influence the physical and ecological dynamics of the Southern Ocean,” said co-author Kyle Mattingly, a postdoctoral researcher at the Rutgers Institute of Earth, Ocean, and Atmospheric Sciences. “They act as giant ‘windows’ in sea ice that allow large amounts of heat to move from the ocean to the atmosphere, changing regional and global ocean circulation. They also influence the timing and extent of phytoplankton (algae) blooms, which are the basis of the marine food web. Our study will pave the way for a greater understanding of climate variability and climate change in these regions. “

Previous studies have found that atmospheric rivers affect the melting of land ice and West Antarctic ice shelves, and the new study builds on these findings by showing their effects on Antarctic sea ice for the first time. Rivers are thousands of miles long, and sea ice holes cover thousands of square miles, usually in specific locations that are triggered by local ocean circulation conditions.

West Antarctica, a huge ice sheet found on land, is melting and contributing to global sea level rise, and melting accelerated in the 21st century. If the entire Antarctic ice sheet melted, the ocean level would rise by about 200 feet, according to the National Snow & Ice Data Center. Rising sea levels and flooding from coastal storms threaten coastal communities around the world, especially in low-lying areas.

Based on predicted future climate change, atmospheric rivers are expected to become more frequent, longer, wider and more effective in moving high levels of water vapor to the Southern Ocean and the continent, along with increasing intensity of rainfall. Overall, the point at which they land is expected to shift towards the poles and the effect of climate change on sea ice holes in the Weddell Sea and elsewhere in the Southern Ocean is an important area for future research.

Reference: “On the crucial role of atmospheric rivers in the two major events of Weddell Polynya in 1973 and 2017 in Antarctica” by Diana Francis, Kyle S. Mattingly, Marouane Temimi, Rob Massom and Petra Heil, 11 November 2020, Advances in science.
DOI: 10.1126 / sciadv.abc2695

Co-authors include scientists from Khalifa University of Science and Technology, the Stevens Institute of Technology and the Australian Antarctic Division, and the Australian Antarctic Program Partnership.