Atmospheric rivers help create sea ice holes

Long “atmospheric rivers” help create massive holes in Antarctic sea ice and may influence ocean conditions around the vast continent, according to new research.

Scientists studied the impact of the intense plumes of warm and moist air that flow to the polar environment from the coast of South America and found that their repeated arrival during winter of 2017 contributed to the development of a sea ice hole (a polynya) in the Weddell Sea region of the Southern Ocean.

Previous studies have found that atmospheric rivers influence melting of West Antarctic land ice and ice shelves, but this is the first, they say, to show their effects on Antarctic sea ice.

The work involved a team from Khalifa University of Science and Technology in the UAE, the Australian Antarctic Division, and Rutgers University and Stevens Institute of Technology in the US. The findings are published in the journal Science Advances.

“Polynyas strongly influence the physical and ecological dynamics of the Southern Ocean,” says co-author Kyle Mattingly, from Rutgers. “They serve as giant windows in the sea ice that allow large amounts of heat to move from the ocean to the atmosphere, modifying regional and global ocean circulation.

“They also affect the timing and magnitude of phytoplankton – algae – blooms, which are the base of the marine food web. Our study will pave the way for greater understanding of climate variability and climate change in these regions.”

Atmospheric rivers can be thousands of kilometres long and the sea ice holes cover thousands of square kilometres, usually at specific locations that are primed by local ocean circulation conditions.

Under projected future climate change, the rivers are predicted to become more frequent, longer, wider and more effective in moving high levels of water vapour toward the Antarctic Ocean and continent, along with increasing the intensity of precipitation, the researchers say.

In general, where they make landfall is predicted to shift toward 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.