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| Titel |
Observed small spatial scale and seasonal variability of the CO2 system in the Southern Ocean |
| VerfasserIn |
L. Resplandy, J. Boutin, L. Merlivat |
| 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 ; 11, no. 1 ; Nr. 11, no. 1 (2014-01-07), S.75-90 |
| Datensatznummer |
250117105
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| Publikation (Nr.) |
 copernicus.org/bg-11-75-2014.pdf |
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| Zusammenfassung |
| The considerable uncertainties in the carbon budget of the Southern
Ocean are largely attributed to unresolved variability, in particular
at a seasonal timescale and small spatial scale
(~ 100 km). In this study, the variability of surface
pCO2 and dissolved inorganic carbon (DIC) at seasonal and small spatial scales is
examined using a data set of surface drifters including ~ 80 000
measurements at high spatiotemporal resolution. On spatial scales of
100 km, we find gradients ranging from 5 to 50 μatm
for pCO2 and 2 to 30 μmol kg−1 for DIC,
with highest values in energetic and frontal regions. This result is
supported by a second estimate obtained with sea surface temperature (SST) satellite images and
local DIC–SST relationships derived from drifter observations. We
find that dynamical processes drive the variability of DIC at small
spatial scale in most regions of the Southern Ocean and the cascade of
large-scale gradients down to small spatial scales, leading to
gradients up to 15 μmol kg−1 over
100 km. Although the role of biological activity is more
localized, it enhances the variability up to 30 μmol kg−1
over 100 km. The seasonal cycle of
surface DIC is reconstructed following Mahadevan et al. (2011), using an
annual climatology of DIC and a monthly climatology of mixed layer
depth. This method is evaluated using drifter observations and proves
to be a reasonable first-order estimate of the seasonality in the
Southern Ocean that could be used to validate model simulations. We
find that small spatial-scale structures are a non-negligible source
of variability for DIC, with amplitudes of about a third of the
variations associated with the seasonality and up to 10 times the
magnitude of large-scale gradients. The amplitude of small-scale
variability reported here should be kept in mind when inferring
temporal changes (seasonality, interannual variability, decadal
trends) of the carbon budget from low-resolution observations and models. |
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