MELBOURNE, Oct. 29 (Xinhua) -- The Antarctic Intermediate Water (AAIW) has rapidly become saltier and denser as Antarctic sea ice loss reduces freshwater input, potentially affecting deep-ocean warming and sea levels, according to new research.
The AAIW, a vast layer of fresh water spanning much of the Southern Hemisphere's ocean, helps store carbon, supply oxygen and drive global ocean currents. It plays a role in heat, freshwater and carbon redistribution around the planet, according to a statement released Wednesday by Australia's University of Melbourne.
The study, published in Nature Climate Change, found that Antarctic summer sea-ice melt helped maintain the AAIW from 1995 to 2015. From 2016, Antarctic sea ice declined to record lows. Between 2016 and 2024, reduced freshwater input led the water layer to become saltier, denser and deeper.
The team analyzed data from the global Argo program, a network of about 4,000 robotic floats that sample the upper oceans, along with satellite and atmospheric datasets.
Researchers said the last time the AAIW underwent a similar shift was at the end of the last interglacial period, around 130,000 years ago, when there was very little ice in Antarctica. However, that transition took thousands of years, rather than two decades.
The researchers said changes in the AAIW could affect the ocean's ability to store carbon and push more excess heat into deeper waters, meaning existing models may underestimate deep-ocean warming and miscalculate regional sea-level rise. ■
