Indian Ocean sector defies global trend with rising oxygen levels

Dissolved oxygen concentrations in the Indian sector of the Southern Ocean (ISSO) have climbed substantially over the past 30 years, according to research conducted by scientists at the National Centre for Polar and Ocean Research (NCPOR) in Goa. The trend represents a marked exception to declining oxygen levels observed across most of the world's oceans.

The study, which examined data spanning 1993 to 2025, identified enhanced ocean ventilation as the primary driver of rising oxygen levels in the ISSO. This process involves the mixing and transport of oxygen-rich surface waters into deeper ocean layers, effectively replenishing oxygen reserves at greater depths. The oxygenation trend proved particularly pronounced in the Polar and Antarctic zones within the Indian sector.

The findings contrast sharply with global patterns, where oxygen depletion has intensified over recent decades. Scientists worldwide have attributed this worldwide deoxygenation to global warming, increased stratification of ocean layers, and weakening ocean circulation systems that reduce the mixing of oxygen-rich and oxygen-poor waters.

The Southern Ocean, which encircles Antarctica and influences planetary climate patterns, serves as a crucial 'lung' for the global ocean system. Its role in carbon cycling and ocean ventilation makes developments in this region significant for understanding broader changes in marine ecosystems and global ocean health.