Carbon Cycling and Air-Sea Interactions in Indian Ocean Systems

The Indian Ocean plays a pivotal role in the global carbon cycle, acting both as a sink and a source for atmospheric carbon dioxide. Monsoon-driven upwelling in the Arabian Sea and differential freshwater inputs in the Bay of Bengal govern nutrient supply, biological productivity and the balance between the biological and solubility pumps. Basin-scale dynamics including the Indian Ocean Dipole and variability in the Indonesian Throughflow modulate sea‐surface temperature, alkalinity and dissolved inorganic carbon, leading to strong interannual and regional differences in air‐sea CO₂ exchange. Seasonal reversals of winds, freshwater discharge from major rivers and episodic events such as tropical cyclones further perturb mixed‐layer depth, vertical mixing and coastal upwelling, altering the partial pressure of CO₂ (pCO₂) at the surface. Observational advances—from in situ time‐series to satellite retrievals—and improvements in biogeochemical modelling are refining estimates of sea‐air CO₂ fluxes, ocean acidification trends and the efficacy of natural carbon sequestration. A comprehensive understanding of these processes underpins projections of climate feedbacks, informs regional carbon budgets and supports management of marine resources in a warming world.

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Carbon Cycling and Air-Sea Interactions in Indian Ocean Systems publication trend

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Technical terms

Partial pressure of CO₂ (pCO₂): Measurement of CO₂ concentration in seawater expressed as the pressure it would exert if it occupied the same volume as a gas.

Air‐sea CO₂ flux: The net rate of carbon dioxide exchange across the ocean surface per unit area, driven by differences in pCO₂ between air and water.

Biological pump: The suite of processes by which marine organisms fix CO₂ into organic matter and transport it to the deep ocean through sinking particles.

Solubility pump: The physical process of CO₂ dissolving in surface water and being transported to depth by ocean circulation and mixing.

Dissolved inorganic carbon (DIC): The total of CO₂, bicarbonate and carbonate ions dissolved in seawater, key to buffering and acidification.

Indian Ocean Dipole (IOD): A climate pattern characterized by opposing sea‐surface temperature anomalies in the western and eastern Indian Ocean, influencing monsoon strength.

Indonesian Throughflow (ITF): A major ocean current system that transports warm, nutrient‐rich water from the Pacific into the Indian Ocean, affecting heat and carbon distributions.

References

1. Sea-surface pCO2 maps for the Bay of Bengal based on advanced machine learning algorithms. Scientific Data (2024).
2. Weakening Indian Ocean carbon uptake in 2015: The role of amplified basin‐wide warming and reduced Indonesian throughflow. Limnology and Oceanography Letters (2024).
3. Biological production in the Indian Ocean upwelling zones –Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models. Biogeosciences (2018).