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| Titel |
The Surface-Forced Overturning of the North Atlantic: Estimates from Modern Era Atmospheric Reanalysis Datasets |
| VerfasserIn |
Jeremy Grist, Simon Josey, Robert Marsh, Young-Oh Kwon, Rory Bingham, Adam Blaker |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088761
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| Publikation (Nr.) |
 EGU/EGU2014-2906.pdf |
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| Zusammenfassung |
| Estimates of the recent mean and time varying water mass transformation rates associated
with North Atlantic surface-forced overturning are presented. The estimates are derived from
heat and freshwater surface fluxes and sea surface temperature fields from six atmospheric
reanalyses (JRA, NCEP-1, NCEP-2, ERA-I, CFSR and MERRA) together with sea surface
salinity fields from two globally gridded data sets (World Ocean Atlas and EN3). The
resulting twelve estimates of the 1979-2007 mean surface-forced streamfunction all depict a
sub-polar cell, with maxima north of 45oN, near Ïă = 27.5 kgm-3, and a sub-tropical cell
between 20oN and 40oN, near Ïă = 26.1 kgm-3. The mean magnitude of the sub-polar cell
varies between 12-18 Sv, consistent with estimates of the overturning circulation
from sub-surface observations. Analysis of the thermal and haline components of
the surface density fluxes indicate large differences in the inferred low latitude
circulation are largely due to the biases in reanalysis net heat flux fields, which
range in the global mean from -13 Wm-2 to 19 Wm-2. The different estimates of
temporal variability in the sub-polar cell are well correlated with each other. This
suggests the uncertainty associated with the choice of reanalysis product does not
critically limit the ability of the method to infer the variability in the sub-polar
overturning. In contrast, the different estimates of sub-tropical variability are poorly
correlated with each other, and only a subset of them capture a significant fraction of the
variability in independently estimated North Atlantic Sub-Tropical Mode Water volume. |
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