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| Titel |
Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea |
| VerfasserIn |
K. Castro-Morales, J. Kaiser |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 8, no. 1 ; Nr. 8, no. 1 (2012-01-04), S.1-10 |
| Datensatznummer |
250005392
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| Publikation (Nr.) |
 copernicus.org/os-8-1-2012.pdf |
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| Zusammenfassung |
| Concentrations of oxygen (O2) and other dissolved gases in the oceanic
mixed layer are often used to calculate air-sea gas exchange fluxes. The
mixed layer depth (zmix) may be defined using criteria based on
temperature or density differences to a reference depth near the ocean
surface. However, temperature criteria fail in regions with strong
haloclines such as the Southern Ocean where heat, freshwater and momentum
fluxes interact to establish mixed layers. Moreover, the time scales of
air-sea exchange differ for gases and heat, so that zmix defined using
oxygen may be different than zmix defined using temperature or density.
Here, we propose to define an O2-based mixed layer depth,
zmix(O2), as the depth where the relative difference between the
O2 concentration and a reference value at a depth equivalent to 10 dbar
equals 0.5 %. This definition was established by analysis of O2
profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and
corroborated by visual inspection. Comparisons of zmix(O2) with
zmix based on potential temperature differences, i.e., zmix(0.2 °C) and zmix(0.5 °C), and potential density differences, i.e.,
zmix(0.03 kg m−3) and zmix(0.125 kg m−3), showed that
zmix(O2) closely follows zmix(0.03 kg m−3). Further
comparisons with published zmix climatologies and zmix derived from
World Ocean Atlas 2005 data were also performed. To establish zmix for
use with biological production estimates in the absence of O2 profiles,
we suggest using zmix(0.03 kg m−3), which is also the basis for the
climatology by de Boyer Montégut et al. (2004). |
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