Antarctic sea-ice loss is making a key ocean layer saltier and deeper
A Nature study reports that Antarctic Intermediate Water is becoming saltier and denser, and its core is moving deeper as declining sea ice reduces the freshwater supply that helps keep it relatively fresh. Lead author Bishakhdatta Gayen told Gizmodo that a comparable transformation last occurred about 130,000 years ago, but unfolded over thousands of years rather than two decades.
Bottom line — The study found Antarctic Intermediate Water’s core salinity is rising by 0.005 grams per kilogram each decade.
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The cold, oxygen-rich water mass forms near Antarctica at depths of roughly 700–1,200 metres, according to Gizmodo.
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Gayen and colleagues analysed observations from nearly 4,000 Argo floats, which record salinity and temperature in the upper 1.9 kilometres of the ocean.
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Antarctic sea ice reached a record high in 2014; a sharp decline began in 2016, reducing the freshwater supply.
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Antarctic Intermediate Water carries nutrients, oxygen, carbon and heat through the Indian, Pacific and Atlantic oceans.
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The researchers say changes to its circulation could affect storm paths, precipitation and sea levels, and potentially reinforce sea-ice loss.