How global warming enhances the Indian Ocean's role as a climate buffer

The Indian Ocean absorbs a significant portion of the CO₂ emitted by human activities each year, but recent satellite observations indicate that the seasonality of this absorption is increasing. Researchers suggest that warming ocean temperatures could transform this basin into a more effective climate buffer, with major implications for global carbon balance.

What the study reveals

Published in Geophysical Research Letters, the study highlights an increase in CO₂ absorption during Australian summers as surface temperatures consistently rise. Authors note that the historically stronger winter carbon uptake is now reversing, enhancing the basin's role as a carbon sink during the warmest period. This inversion is associated with changes in surface layer stratification, favoring greater gas dissolution in warm waters.

Moreover, researchers note that prediction uncertainty around these processes is decreasing due to the integration of new datasets. Traditional climate models, which often underestimated the role of regional ocean currents, are now adjusted to account for these enhanced seasonal dynamics. The result is a scenario where the Indian Ocean could absorb several tens of gigatonnes of additional CO₂ over the coming decades, according to the most optimistic simulations.

How

The team combined satellite data from the Copernicus mission with ECMWF reanalyses, enriched by the predictive model GraphCast and neural network Pangu-Weather. These machine learning tools enabled the reconstruction of temperature, salinity, and CO₂ concentration fields with unprecedented resolution. By training the model on decades of observations, scientists reduced prediction uncertainty of seasonal carbon absorption by around 15%.

The analysis process relies on the exploitation of atmospheric and oceanic data, including surface carbon flux measurements, chlorophyll variations, and wind dynamics changes. Through machine learning, the model identified subtle correlations between rising surface temperatures and intensifying upwelling currents transporting carbon to depths. This hybrid approach, combining neural networks and physical models, represents a major advance in understanding.