Sensitivity of simulated extent and future evolution of marine suboxia to mixing intensity.

Duteil, Olaf and Oschlies, Andreas (2011) Sensitivity of simulated extent and future evolution of marine suboxia to mixing intensity. Open Access Geophysical Research Letters, 38 (6). L06607. DOI 10.1029/2011GL046877.

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Abstract

Geological and hydrographic records contain evidence of substantial past variations in the oxygenation of the global ocean. Numerical models predicts a future decrease of marine oxygen levels under global warming. Using a global biogeochemical-climate model in which diapycnal mixing is parametrised as the sum of the regionally heterogenous tidal and homogenous background vertical mixing, we here show that simulated total oceanic oxygen content and the extent of marine suboxia are both sensitive to the strength of background vertical mixing. Eight otherwise identical configurations of the model were spun up under pre-industrial conditions for different vertical diffusivities ranging from background values of 0.01 cm 2/s to 0.5 cm 2/s. This range corresponds to various observational estimates and to values currently used in numerical ocean circulation models. Whereas the simulated total oceanic oxygen content is larger for larger mixing intensities, the simulated suboxic volume displays a maximum at intermediate diffusivities of about 0.2 cm 2/s. The intensity of vertical mixing also determines the evolution of suboxic areas under projected 21st century CO 2 emissions: while all model configurations predict a decline in total oceanic oxygen, the simulated extent of marine suboxia shows a 21st century expansion only for mixing rates higher than 0.2 cm 2/s, whereas the suboxic volume declines for lower mixing rates despite an overall loss of marine oxygen. Differences in the poorly constrained mixing parameterisation can thus lead to qualitatively different estimates about the future evolution of marine suboxia under projected climate change.

Document Type: Article
Keywords: Biogeochemistry; Ocean interior mixing estimates range from one magnitude order; Suboxia extension is maximal at intermediate mixing; Future suboxia can increase or decrease by 50% depending of interior mixing
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > SFB 754
OceanRep > SFB 754 > B1
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2011GL046877
ISSN: 0094-8276
Projects: SFB754
Expeditions/Models/Experiments:
Date Deposited: 27 Apr 2011 11:59
Last Modified: 23 Sep 2019 17:50
URI: http://oceanrep.geomar.de/id/eprint/11822

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