BENGALURU: A team of researchers has found that salinity in intermediate water in the Antarctic sea is increasing, and ice is melting.
Researchers said this will impact aquatic life and the weather pattern, particularly the Indian monsoon. They noted that the Antarctic Intermediate Water (AAIW) had become saltier and more dense since 2015, because of the sharp decline in Antarctic sea ice.
In the study ‘Reversal of Antarctica Intermediate Water trends triggered by sea ice decline’, researchers said AAIW is a key component of the global overturning circulation.
The study noted that the saltier AAIW causes disruption in how ocean layers are stratified. It allows stored carbon to escape into the atmosphere more easily, thus contributing to increased warming.
Researchers from the Centre for Atmospheric and Oceanic Sciences at the Indian Institute of Science, along with their counterparts at the University of Melbourne and the University of Southampton, conducted the study. The report was released on Wednesday, it has been published in Nature Climate Change journal.
The researchers noted that sustained sea ice expansion over several decades up to 2015 has enhanced summertime meltwater input, stratifying the upper polar ocean and freshening the AAIW.
The report explained that AAIW forms in the southern ocean and spreads northward through the Atlantic, Indian and Pacific Oceans, hundreds of metres below the surface.
“Changes to this water mass can carry the effects of changes near Antarctica far beyond the polar region,” said Kaushik Mishra, co-author of the report.
They noted that reduced freshwater from melting sea ice is linked to the upward movement of warmer and saltier water from the ocean’s depths. Bishakhdatta Gayen, Associate Professor, COAS, IISc, co-author of the study, added that freshwater from Antarctic sea ice melt helps maintain a relatively fresh layer of cold water near the surface.
This water mixes with deeper water and sinks beneath the surface, contributing to the AAIW as it moves northward. The layer of cold water formed during the Antarctic winter, known as ‘winter water’.
When less meltwater enters the system and more salty deep water reaches the upper ocean, the balance changes. The water feeding into the AAIW becomes saltier and denser, he added.