SENSITIVITY OF OXYGEN MINIMUM ZONES DUE TO CARBON DIOXIDE RADIATIVE FORCINGS

Anthropogenic-induced climate change is occurring at an unprecedented rapid rate, compared to the geologic past. In this study, CO₂ stabilization scenarios (1x, 2x, and 4x preindustrial atmospheric pCO₂ levels) utilizing the Community Earth System Model (CESM) are carried out to assess the response of oxygen minimum zones to net primary production and vertical carbon fluxes in a changing climate. For the 4x CO₂ scenario, compared to the 1x CO₂ experiment, a rise in sea surface temperature of 3°C to 5°C, particularly between 30°S and 60°S, in the Pacific and Atlantic Ocean is simulated, whereas in the North Atlantic and around Greenland, a cooling up to 6.5°C occurs linked to the weakening of the Atlantic meridional overturning circulation (AMOC). In the 4x scenario, export production decreases in the northern Atlantic Ocean, consistent to the cooling and reduced AMOC, and also in the central equatorial Atlantic and Pacific Ocean due to reduced Ekman-induced upwelling and associated decline in surface nutrient concentration. In contrast, export production increases in the region of the Antarctic Circumpolar Current (ACC) linked to a rise in surface PO₄ concentration. Surface nitrates (NO₃) decrease globally, especially along the equator. Dissolved oxygen concentration at intermediate depth of equatorial Atlantic and Pacific Ocean water masses decreases from 1x CO₂ to the 4x CO₂ linked to both a decrease in apparent oxygen utilization (AOU) and decline in oxygen solubility by the warming.