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Natural variability and anthropogenic trends in oceanic oxygen in a coupled carbon cycle–climate model ensemble
Author(s) -
Frölicher T. L.,
Joos F.,
Plattner G.K.,
Steinacher M.,
Doney S. C.
Publication year - 2009
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2008gb003316
Subject(s) - climatology , pacific decadal oscillation , volcano , environmental science , forcing (mathematics) , climate model , climate change , atlantic multidecadal oscillation , carbon cycle , oceanography , geology , north atlantic oscillation , sea surface temperature , atmospheric sciences , ecosystem , ecology , seismology , biology
Internal and externally forced variability in oceanic oxygen (O 2 ) are investigated on different spatiotemporal scales using a six‐member ensemble from the National Center for Atmospheric Research CSM1.4‐carbon coupled climate model. The oceanic O 2 inventory is projected to decrease significantly in global warming simulations of the 20th and 21st centuries. The anthropogenically forced O 2 decrease is partly compensated by volcanic eruptions, which cause considerable interannual to decadal variability. Volcanic perturbations in oceanic oxygen concentrations gradually penetrate the ocean's top 500 m and persist for several years. While well identified on global scales, the detection and attribution of local O 2 changes to volcanic forcing is difficult because of unforced variability. Internal climate modes can substantially contribute to surface and subsurface O 2 variability. Variability in the North Atlantic and North Pacific are associated with changes in the North Atlantic Oscillation and Pacific Decadal Oscillation indexes. Simulated decadal variability compares well with observed O 2 changes in the North Atlantic, suggesting that the model captures key mechanisms of late 20th century O 2 variability, but the model appears to underestimate variability in the North Pacific. Our results suggest that large interannual to decadal variations and limited data availability make the detection of human‐induced O 2 changes currently challenging.