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| Titel |
Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends |
| VerfasserIn |
A. Cabré, I. Marinov, R. Bernardello, D. Bianchi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 18 ; Nr. 12, no. 18 (2015-09-21), S.5429-5454 |
| Datensatznummer |
250118098
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| Publikation (Nr.) |
 copernicus.org/bg-12-5429-2015.pdf |
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| Zusammenfassung |
We analyse simulations of the Pacific Ocean oxygen minimum zones (OMZs) from
11 Earth system model contributions to the Coupled Model Intercomparison
Project Phase 5, focusing on the mean state and climate change projections.
The simulations tend to overestimate the volume of the OMZs, especially in
the tropics and Southern Hemisphere. Compared to observations, five models
introduce incorrect meridional asymmetries in the distribution of oxygen
including larger southern OMZ and weaker northern OMZ, due to
interhemispheric biases in intermediate water mass ventilation. Seven models
show too deep an extent of the tropical hypoxia compared to observations,
stemming from a deficient equatorial ventilation in the upper ocean, combined
with too large a biologically driven downward flux of particulate organic
carbon at depth, caused by particle export from the euphotic layer that is too high
and remineralization in the upper ocean that is too weak.
At interannual timescales, the dynamics of oxygen in the eastern tropical
Pacific OMZ is dominated by biological consumption and linked to natural
variability in the Walker circulation. However, under the climate change
scenario RCP8.5, all simulations yield small and discrepant changes in
oxygen concentration at mid depths in the tropical Pacific by the end of the
21st century due to an almost perfect compensation between
warming-related decrease in oxygen saturation and decrease in biological
oxygen utilization. Climate change projections are at odds with recent
observations that show decreasing oxygen levels at mid depths in the
tropical Pacific.
Out of the OMZs, all the CMIP5 models predict a decrease of oxygen over most
of the surface and deep ocean at low latitudes and over all depths at high latitudes due to an overall slow-down of
ventilation and increased temperature. |
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