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Title: Sensitivity of Global Ocean Deoxygenation to Vertical and Isopycnal Mixing in an Ocean Biogeochemistry Model

Journal Article · · Global Biogeochemical Cycles
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]
  1. Georgia Institute of Technology, Atlanta, GA (United States); Georgia Institute of Technology
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Princeton Univ., NJ (United States)
  4. National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
+ Show Author Affiliations

Large-scale loss of oxygen under global warming is termed “ocean deoxygenation” and is caused by the imbalance between physical supply and biological consumption of oxygen in the ocean interior. Significant progress has been made in the theoretical understanding of ocean deoxygenation; however, many questions remain unresolved. The oxygen change in the tropical thermocline is poorly understood, with diverging projections among different models. Physical oxygen supply is controlled by a suite of processes that transport oxygen-rich surface waters into the interior ocean, which is expected to weaken due to increasing stratification under global warming. Using a numerical model and a series of sensitivity experiments, the role of ocean mixing is examined in terms of effects on the mean state and the response to a transient warming. Both vertical and horizontal (isopycnal) mixing coefficients are systematically varied over a wide range, and the resulting oxygen distributions in equilibrated and transient simulations are examined. The spatial patterns of oxygen loss are sensitive to both vertical and isopycnal mixing, and the sign of tropical oxygen trend under climate warming can reverse depending on the choice of mixing parameters. An elevated level of isopycnal mixing disrupts the vertical advective-diffusive balance of the tropical thermocline, increasing the mean state oxygen as well as the magnitude of the transient oxygen decline. These results provide first-order explanations for the diverging behaviors of simulated tropical oxygen with respect to ocean mixing parameters.

Research Organization:
Georgia Institute of Technology, Atlanta, GA (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF)
Grant/Contract Number:
SC0021300
OSTI ID:
1864678
Alternate ID(s):
OSTI ID: 1864915; OSTI ID: 1866961
Report Number(s):
LA-UR-21-27311; 1737158; 1737188; 1737282
Journal Information:
Global Biogeochemical Cycles, Journal Name: Global Biogeochemical Cycles Journal Issue: 4 Vol. 36; ISSN 0886-6236
Publisher:
American Geophysical Union (AGU)Copyright Statement
Country of Publication:
United States
Language:
English

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