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| Titel |
Influence of Southern Ocean seasonal variability on the western North Atlantic |
| VerfasserIn |
Vladimir Ivchenko, Bablu Sinha, Neil Wells, Mitsuhiro Kawase, Vladimir Zalesny, Jeremy Grist, Adam Blaker, Beverly De Cuevas |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034251
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| Zusammenfassung |
| The huge seasonal variability in Antarctic sea ice extent is well known. The seasonal
variation is approximately 18x106 km2, an area larger than that of Antarctica and its ice
shelves. We demonstrate that the pronounced variability in the Antarctic influences other
regions of the World Ocean on timescales of months to years. Particularly strongly influenced
are the equatorial regions; the western boundary currents, such as the Gulf Stream
and the Kuroshio; and parts of the Arctic. The mechanism involves propagation of
planetary waves and their interaction with boundaries and strong currents. The
effectiveness of this mechanism in connecting the Southern Ocean with the Equatorial
Pacific has been described by Atkinson et al. (Geophys. Res. Lett., 36, L08603,
doi:10.1029/2008GL036976) and other earlier studies. In the present study we analyze the
western North Atlantic, including the Gulf Stream, using two simulations with the Global
Ocean General Circulation Model NEMO (Nucleus for European Modelling of the
Ocean) at 1/4Ë horizontal resolution. A control experiment simulates the ocean
state for the period 1989-1994. A perturbed experiment is identical except surface
fluxes from/to the atmosphere south of 40Ë S are replaced by an annual mean.
Between 40Ë S and 30Ë S the seasonal component of forcing is gradually increased to
the unperturbed value to ensure a smooth transition between the region with and
without seasonal forcing. Anomalies of temperature, salinity and velocity are obtained
by subtracting the results of these two experiments. The experiments clearly and
unambiguously demonstrate and quantify the remote effects of the Southern Ocean
variability. There is a reasonably strong seasonal modulation of the temperature,
salinity and kinetic energy in the Gulf-Stream area. The anomalies are statistically
significant, i.e. bigger than standard error for each of the runs and stand out above eddy
variability. The anomaly of the Atlantic Meridional Overturning Circulation (MOC)
is persistent between 20Ë N and 40Ë N, reaching about 1 Sv for annual means. |
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