3-7 September 2018
Audimax | Kiel University
Europe/Berlin timezone

Mechanisms of low-frequency oxygen variability in the North Pacific

3 Sep 2018, 14:45
Audimax-Hörsaal-D (Kiel University)


Kiel University



Taka Ito (Georgia Institute of Technology)


This study investigates the mechanisms of interannual and decadal variability of dissolved oxygen (O$_2$) in the North Pacific using historical bottle O$_2$ data and a physical-biogeochemical hindcast simulation. An ocean-ice configuration of the Community Earth System Model (CESM) is used to for the hindcast. The simulated variability of upper ocean (200m) O$_2$ is broadly consistent with observations in the western and eastern Pacific where sampling density is relatively higher. The dominant mode of O$_2$ variability in this depth range explains 24.8% of the variance and is significantly correlated with the Pacific Decadal Oscillation (PDO) index (${r=0.68}$). Two major mechanisms are proposed as null hypotheses by which the PDO controls O$_2$ variability. Vertical movement of isopycnals (``heave'') may drive O$_2$ variability in deep tropics. Isopycnal surfaces are depressed in the eastern tropics under the positive (El Nino-like) phase of PDO, leading to O$_2$ increases in the upper water column. In contrast to the tropics, changes in subduction associated with the PDO are the primary control on extra-tropical O$_2$ variability. These hypotheses are tested by contrasting the anomalies of O$_2$ and heave-induced O$_2$ where the latter is calculated from potential density anomalies. At 200m depth, isopycnal heave is the leading control on O$_2$ variability except for the central subtropics, downstream of the subduction region. Further examination of the amplitude of O$_2$ anomealies reveals that the null hypothesis cannot fully explain the tropical O$_2$ variability, likely indicating the reinforcing changes in the biological O$_2$ consumption. These mechanisms, synchronized with the PDO, develops a basin-scale pattern of O$_2$ variability that are comparable in magnitude to the projected rates of ocean deoxygenation in this century.

Affiliation Georgia Institute of Technology
Position Professor
Email Address taka.ito@eas.gatech.edu
Are you a SFB 754 / Future Ocean member? No

Primary author

Taka Ito (Georgia Institute of Technology)


Dr Matthew C. Long (National Center for Atmospheric Research) Prof. Curtis Deutsch (University of Washington) Shoshiro Minobe (Hokkaido University) Mr Daoxun Sun (Georgia Institute of Technology)

Presentation Materials