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| Titel |
Controlling factors of the oxygen balance in the Arabian Sea's OMZ |
| VerfasserIn |
L. Resplandy, M. Lévy, L. Bopp, V. Echevin, S. Pous, V. V. S. S. Sarma, D. Kumar |
| 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 ; 9, no. 12 ; Nr. 9, no. 12 (2012-12-13), S.5095-5109 |
| Datensatznummer |
250007459
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| Publikation (Nr.) |
 copernicus.org/bg-9-5095-2012.pdf |
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| Zusammenfassung |
The expansion of OMZs (oxygen minimum zones) due to climate change and their possible evolution and
impacts on the ecosystems and the atmosphere are still debated, mostly
because of the unability of global climate models to adequatly reproduce the
processes governing OMZs. In this study, we examine the factors controlling
the oxygen budget, i.e. the equilibrium between oxygen sources and sinks in
the northern Arabian Sea OMZ using an eddy-resolving biophysical model.
Our model confirms that the biological consumption of oxygen is most intense
below the region of highest productivity in the western Arabian Sea. The
oxygen drawdown in this region is counterbalanced by the large supply of
oxygenated waters originated from the south and advected horizontally by the
western boundary current. Although the biological sink and the dynamical
sources of oxygen compensate on annual average, we find that the seasonality
of the dynamical transport of oxygen is 3 to 5 times larger than the
seasonality of the biological sink. In agreement with previous findings, the
resulting seasonality of oxygen concentration in the OMZ is relatively weak,
with a variability of the order of 15% of the annual mean oxygen
concentration in the oxycline and 5% elsewhere. This seasonality primarily
arises from the vertical displacement of the OMZ forced by the monsoonal
reversal of Ekman pumping across the basin. In coastal areas, the oxygen
concentration is also modulated seasonally by lateral advection. Along the
western coast of the Arabian Sea, the Somali Current transports oxygen-rich
waters originated from the south during summer and oxygen-poor waters from
the northeast during winter. Along the eastern coast of the Arabian Sea, we
find that the main contributor to lateral advection in the OMZ is the Indian
coastal undercurrent that advects southern oxygenated waters during summer
and northern low-oxygen waters during winter. In this region, our model
indicates that oxygen concentrations are modulated seasonally by coastal
Kelvin waves and westward-propagating Rossby waves.
Whereas on seasonal time scales the sources and sinks of oxygen are dominated
by the mean vertical and lateral advection (Ekman pumping and monsoonal
currents), on annual time scales we find that the biological sink is
counterbalanced by the supply of oxygen sustained by mesoscale structures
(eddies and filaments). Eddy-driven advection hence promotes the vertical
supply of oxygen along the western coast of the Arabian Sea and the lateral
transport of ventilated waters offshore the coast of Oman and southwest
India. |
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