A hidden ocean change near Antarctica could have global consequences
Summary
Researchers found that a deep layer of Southern Ocean water around Antarctica has become saltier since 2016, reversing decades of freshening. The layer carries heat, carbon, oxygen and nutrients toward other oceans, so the shift may affect global ocean circulation and climate, though scientists say they need more observations to determine whether it will persist.Key Facts
- The study tracked Southern Ocean changes from 2004 to 2024 using six independent datasets, including measurements from Argo floats.
- The affected Antarctic Intermediate Water layer lies about 2,300 to 4,000 feet below the surface and encircles Antarctica.
- Antarctic sea ice fell sharply after reaching a satellite-era high in 2014; it hit a record low in 2016 and another low in 2023.
- In 2023, Antarctic sea ice measured about 1 million square miles below the 1981–2010 average.
- Researchers say dwindling sea ice leaves less freshwater during the melt season, contributing to higher salinity in the water layer.
- Antarctic Intermediate Water spreads into the Indian, Pacific and Atlantic oceans, carrying heat, carbon, oxygen and nutrients toward the tropics and across the equator.
- Changes in the layer’s density, thickness and salinity can affect how the ocean moves and stores heat.
- Scientists say the observational record is too short to know whether the shift is permanent.
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