HR: 16:45h
AN: OS24B-04    [Abstracts]
TI: Attributing the causes of North Pacific oxygen change
AU: * Deutsch, C
EM: cdeutsch@ocean.washington.edu
AF: Department of Oceanography, University of Washington, Box 355351, Seattle, WA 98105 United States
AU: Emerson, S
EM: emerson@u.washington.edu
AF: Department of Oceanography, University of Washington, Box 355351, Seattle, WA 98105 United States
AU: Thompson, L
EM: luanne@ocean.washington.edu
AF: Department of Oceanography, University of Washington, Box 355351, Seattle, WA 98105 United States
AB: We investigate the variability of dissolved oxygen in the upper water column of the North Pacific using a hind cast model simulation. The model applies the biogeochemical framework of the Ocean Carbon Model Intercomparison Project (OCMIP) to an isopycnal General Circulation Model (GCM) whose circulation is forced at the surface by historical atmospheric conditions from 1948-2000. Simulated O2 changes from the 1980's to the 1990's include O2 decreases in the subpolar region, especially in the lower ventilated thermocline, and O2 increases over much of the subtropics. Both of these features are similar in pattern and magnitude to those observed along repeat transects through the subtropical and subpolar gyres [Emerson et al. 2004]. We perform a set of additional simulations designed to separate the contributions of changes in biology, ventilation, and circulation to O2 variability. We find that the direct effect of circulation variability, including a southward expansion of the subtropical gyre, is the dominant cause of O2 changes over much of the North Pacific. Variations in thermocline ventilation lead to significant O2 decreases in the Subarctic Northwest Pacific, and the impact of changes in biological export production are confined to the upper thermocline. Simulated O2 changes involve both long-term trends, such as the decreased Subarctic O2 due to reduced ventilation, as well as transient responses to short-term perturbations, many of which occurred in the 1970's.
DE: 4805 Biogeochemical cycles (1615)
DE: 4808 Chemical tracers
DE: 4215 Climate and interannual variability (3309)
DE: 4255 Numerical modeling
DE: 1615 Biogeochemical processes (4805)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting