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Title: Mechanisms of Low‐Frequency Oxygen Variability in the North Pacific
This study investigates the mechanisms of interannual and decadal variability of dissolved oxygen (O2) in the North Pacific using historical observations and a hindcast simulation using the Community Earth System Model. The simulated variability of upper ocean (200 m) O2is moderately correlated with observations where sampling density is relatively high. The dominant mode of O2variability explains 24.8% of the variance and is significantly correlated with the Pacific Decadal Oscillation (PDO) index (r = 0.68). Two primary mechanisms are hypothesized by which the PDO controls upper ocean O2variability. Vertical movement of isopycnals (“heave”) drives O2variations in the deep tropics; isopycnal surfaces are depressed in the eastern tropics under the positive (El Niño‐like) phase of PDO, leading to O2increases in the upper water column. In contrast to the tropics, changes in subduction are the primary control on extratropical O2variability. These hypotheses are tested by contrasting O2anomalies with the heave‐induced component of variability calculated from potential density anomalies. Isopycnal heave is the leading control on O2variability in the tropics, but heave alone cannot fully explain the amplitude of tropical O2variability, likely indicating reinforcing changes from the biological O2consumption. Midlatitude O2variability indeed reflects ocean ventilation downstream of the subduction region where O2anomalies are correlated with the depth of winter mixed layer. These mechanisms, synchronized with the PDO, yield a basin‐scale pattern of O2variability that are comparable in magnitude to the projected rates of ocean deoxygenation in this century under “unchecked” emission scenario.  more » « less
Award ID(s):
1737188
PAR ID:
10453573
Author(s) / Creator(s):
 ;  ;  ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Global Biogeochemical Cycles
Volume:
33
Issue:
2
ISSN:
0886-6236
Page Range / eLocation ID:
p. 110-124
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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