This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The world's oceans help slow climate change by absorbing carbon dioxide (CO₂) from the atmosphere, but how much they take up can vary throughout the year. New research, published in Geophysical Research Letters, suggests these seasonal patterns are changing across the Indian Ocean, potentially affecting how it helps to regulate Earth's climate.
CO₂ moves continuously between the ocean and the atmosphere. When seawater absorbs more CO₂ than it releases, the ocean acts as a carbon sink, storing some of the greenhouse gas that would otherwise remain in the atmosphere and contribute to global warming. But the exchange also works in reverse: The ocean can release dissolved CO₂ back into the air.
This balance is influenced by several factors, including water temperature, winds and ocean circulation. These processes change throughout the year, with seasonal shifts in temperature, winds and the movement of water altering how quickly CO₂ enters or leaves the ocean. Cooler water can generally hold more dissolved CO₂ than warmer water, favoring absorption from the atmosphere, while warming can encourage the gas to escape.
However, the outcome also depends on how much CO₂ is already dissolved in the water and how ocean currents bring carbon-rich water to the surface. According to the Global Carbon Budget 2024, the ocean absorbed around 26% of total human-caused CO₂ emissions between 2014 and 2023. However, research suggests its capacity to absorb additional carbon has shown little growth since 2016, partly because of increased climate variability.
Understanding how the ocean's carbon exchange changes over different timescales is therefore important for predicting how it will respond to continued warming. To investigate these changes, Dr. Apurva Padamanbh Joshi, of the Indian National Center for Ocean Information Services, and colleagues analyzed data from 1980 to 2019 to examine how seasonal CO₂ exchange had evolved across the Indian Ocean.
They found that seasonal variation increased by 48% in the equatorial Indian Ocean and 23% in the southern Indian Ocean, meaning the contrast between different parts of the year became more pronounced in these regions. In the Arabian Sea, however, seasonal variation decreased by 14%, indicating a smaller difference between seasonal highs and lows in carbon exchange. The Bay of Bengal showed a more modest increase in seasonal variation of around 7%.
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