Quantifying the Contribution of Ocean Mesoscale Eddies to Low Oxygen Extreme Events. Issue 15 (5th August 2022)

• Record Type: Journal Article
• Authors: Atkins, Jamie; Andrews, Oliver; Frenger, Ivy
• Is Part Of: Geophysical research letters. Volume 49:Issue 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-05
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL098672
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Ocean mesoscale eddies have been identified as drivers of localized extremely low dissolved oxygen concentration ([O2 ]) conditions in the subsurface. We employ a global physical‐biogeochemical ocean model at eddy‐permitting resolution to conduct a census of open‐ocean eddies near Eastern Boundary Upwelling Systems adjacent to tropical Oxygen Minimum Zones (OMZs). We track cyclonic and anticyclonic eddies with a surface signature over the period 1992–2018 and isolate their subsurface oxygen characteristics. We identify strongly deoxygenating eddies and quantify their contribution to low [O2 ] extreme events. Our results show that model simulated low [O2 ] extreme event frequency is 2–7 times higher in eddies versus non‐eddying locations, with regionally more than half of low [O2 ] extreme events outside of the permanent OMZs being associated with eddies. Our study highlights the need for further work to investigate the drivers, characteristics and potential ecosystem impacts of low [O2 ] extreme events. Plain Language Summary: Over the recent past the oxygen content of the global ocean has been declining, with consequences for marine ecosystems. Ocean eddies (rotating currents of water on the order ≈100 km diameter) have been identified as vehicles of extremely low oxygen concentrations but are understudied in the context of biogeochemical extreme events in the ocean. This investigation is the first of its kind to use a four‐dimensional data set (time, latitude, longitude, depth) to create a regional scale census of eddies and their oxygen conditions across the period 1992–2018 as they travel offshore from typically low oxygen waters of the near‐coastal Atlantic and Pacific, carrying and modifying low oxygen signals into otherwise more oxygenated ocean regions. We track eddies associated with low oxygen conditions and assess how much they contribute to low oxygen extreme events. In some places eddies contribute to more than half of the simulated low oxygen extreme events, signaling the need to further explore the role that eddies play in marine extreme events. Key Points: Eddies contribute substantially to low [O2 ] extreme events near Eastern Boundary Upwelling System regions Low [O2 ] extreme events occur more frequently in eddies versus non‐eddying locations Cyclonic eddies tend to contain lower oxygen concentrations than anticyclonic eddies