Climate models predict that as the planet warms, so will the Southern Ocean. But for decades, the waters around Antarctica have grown mysteriously cooler. A new study shows why.
With warming, the region is seeing more rainfall and more ice melt, which are introducing more freshwater into the Southern Ocean. Because freshwater is not as dense as saltwater, it stays on the surface of the ocean instead of sinking down below. Freshwater acts like a lid, keeping warmer waters from rising up, scientists say, and the effect is much greater than previously appreciated.
Until now, models have failed to fully account for the influence of rain and, in particular, melting. Study coauthor Earle Wilson, of Stanford University, said the impact of meltwater is “completely missing from most climate models.”
Missing freshwater, he and colleagues found, accounts for 60 percent of the mismatch between predicted and actual temperatures. The findings were published in Geophysical Research Letters.
“There’s been some debate over whether that meltwater is enough over the historical period to really matter,” said lead study author Zachary Kaufman, also of Stanford. “We show that it does.”
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