Briny warm water is mixing on the surface of the ocean, making sea ice melt faster, a new study found.
Some of the water around Antarctica has been getting saltier. And that has affected the amount of sea ice at the bottom of the planet.
A study published Monday in the Proceedings of the National Academy of Sciences found that increases in salinity in seawater near the surface could help explain some of the decrease in Antarctic sea ice that have been observed over the past decade, reversing a previous period of growth.
“The impact of Antarctic ice is massive in terms of sea-level rise, in terms of global warming, and therefore, in terms of extremes,” said Alessandro Silvano, a senior scientist at the University of Southampton studying the Southern Ocean and lead author of the study. The findings mean “we are entering a new system, a new world,” he said.
Each year, the sea ice floating atop the Earth’s polar oceans melts in the summer and refreezes in the winter, acting as a mirror that bounces the sun’s heat back into space. Since the late 1970s, as global temperatures ratcheted upward, sea ice in the Arctic has been swiftly declining. But in the Antarctic sea ice continued to grow into the 2010s.
The study used data from satellites to track changes by using a brightness measurement that subtly correlates to salt content. But because the signal is small and easily drowned out by other factors, Dr. Silvano said, it wasn’t possible analyze them effectively until recent advances in algorithms.
When Dr. Silvano and his coauthors first noticed the rising salinity, they doubted the signal was real, suspecting an error in the satellite data. But as physical measurements from ocean instruments began to confirm the trend, they realized the signal was accurate.