DISSOLVED oxygen levels in the Indian sector of the Southern Ocean (ISSO) have significantly risen over the past three decades, even as oceans elsewhere are showing the trend of declining oxygen levels, a study by scientists at a Goa-based institute has found. The scientists attributed the oxygenation primarily to enhanced ocean ventilation - the process through which surface waters are mixed and transported into the ocean interior, replenishing oxygen at greater depths. Oxygenation in the ISSO intensified between 1993 and 2025, particularly in the Polar and Antarctic zones, as per the study conducted by researchers from the National Centre for Polar and Ocean Research (NCPOR), Goa. The findings stand in contrast to the broader trend of declining oxygen levels in oceans worldwide, which scientists have linked to global warming, increased ocean stratification and weakening circulation. “The Southern Ocean acts as the primary ‘lung’ of the global ocean and plays a defining role in regulating global heat, carbon, nutrients and oxygen. Changes in its circulation and ventilation can therefore have implications for the global ocean oxygen inventory,” NCPOR’s Director Dr Thamban Meloth told PTI.