A four-decade analysis found that seasonal swings in CO₂ exchange grew sharply in the equatorial Indian Ocean but weakened in the Arabian Sea, revealing an uneven regional pattern rather than a uniform shift across the basin.
Researchers analyzed an observationally constrained dataset covering 1980 to 2019 for a study published in Geophysical Research Letters. The seasonal amplitude—the difference between stronger and weaker parts of the year—increased by about 48% in the equatorial Indian Ocean and 23% in the southern Indian Ocean. In contrast, it declined by roughly 14% in the Arabian Sea, while the Bay of Bengal saw a smaller increase of about 7%.
The researchers also found changes in average exchange: the ocean’s mean CO₂ source strength decreased in the equatorial Indian Ocean, Bay of Bengal and Arabian Sea, while the southern Indian Ocean’s carbon sink strengthened. That distinction matters because bigger seasonal swings do not, by themselves, mean a region absorbs more CO₂ overall. Temperature, winds and ocean circulation can all influence how much CO₂ moves between seawater and the atmosphere through the year.
The findings show why regional patterns and annual averages both matter when assessing how the Indian Ocean’s carbon exchange is changing.