Environmental Research Letters· 2026Q1
Trends and drivers of recent oxygenation in the Indian Sector of the Southern Ocean
- 1citations
- Q1SCImago
- 2026year
Short summary
The Indian Sector of the Southern Ocean (ISSO) has experienced significant oxygenation from 1993-2025, particularly in the Polar and Antarctic Zones, driven by weakening stratification and increased ventilation of deeper waters.
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Key points
- Significant oxygenation trends observed in the Indian Sector of the Southern Ocean (ISSO) from 1993-2025.
- Elevated dissolved oxygen and shoaling of the oxygen minimum layer noted between 2011 and 2025.
- Warming and salinification weaken stratification, promoting Circumpolar Deep Water shoaling and enhanced ventilation.
- Declining Apparent Oxygen Utilization indicates enhanced ventilation, not solubility changes, as the primary driver.
- Oxygenation spans multiple water masses, indicating a basin-wide ventilation reorganization.
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Abstract
Abstract Integrating in-situ observations from austral summers 2011 and 2025 with satellite and reanalysis data (1993-2025), we document significant oxygenation across the Indian Sector of the Southern Ocean (ISSO), with the strongest trends in the Polar (PZ) and Antarctic Zones (AZ). Observations along 57.5°E reveal elevated dissolved oxygen (DO), poleward retreat of the Winter Water (WW) layer, and partial shoaling of the oxygen minimum layer in 2025 relative to 2011. Combined effect of warming and salinification weaken stratification and promote Circumpolar Deep Water (CDW) shoaling, driving enhanced ventilation and oxygenation. Declining Apparent Oxygen Utilization (AOU) is consistent with enhanced ventilation, not solubility changes, as the dominant mechanism. Oxygenation spans from Antarctic Surface Water (AASW) and WW through Subantarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW), and CDW to Antarctic Bottom Water (AABW), indicating basin-wide ventilation reorganization. These findings contrast with widespread global ocean deoxygenation and highlight the importance of Southern Ocean ventilation for the global ocean oxygen inventory.
The authors' abstract, as published at the source. Environmental Research Letters, 2026 · DOI ↗
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OceanographyEarth and Planetary Sciences