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| Titel |
Observed and simulated variability of the Atlantic meridional overturning circulation and the deep western boundary current |
| VerfasserIn |
Charlotte Mielke, Eleanor Frajka-Williams, Stefan Gary, Kenji Shimizu, John Toole, Johanna Baehr |
| 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 |
250089140
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| Publikation (Nr.) |
 EGU/EGU2014-3332.pdf |
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| Zusammenfassung |
| Despite the importance of Atlantic meridional overturnig circulation (AMOC) for the climate
of Africa, America and Europe, continuous AMOC observations are at present
restricted to two latitudes, and are available for less than ten years. We therefore
investigate whether the AMOC’s variability can be inferred from measurements of the
deep western boundary current (DWBC), which are already available at several
locations.
To that end, we jointly analyze the available 26°N RAPID and the 41°N Argo-based
AMOC estimates with RAPID and line W (40°N) DWBC estimates. We also compare them
to a 60-year simulation with a high-resolution NCEP-forced ocean model. The
DWBC and its layers are defined dynamically in the model based on a comparison of
temperature-versus-salinity data in model and observations and the time-dependent
velocity field. On the timescales where observations are available, the model is
able to reproduce the variability of the DWBC and its individual layers at both
locations.
Our preliminary analysis of the observational data and model results suggests that
different mechanisms dominate the DWBC’s variability at different timescales. On
sub-seasonal to seasonal timescales, the DWBC is mostly barotropic, and its variability is
linked to local processes. Thus, the DWBC has a well-defined seasonal cycle which is
opposite to the seasonal cycle of the non-Ekman component of the AMOC seasonal cycle. On
interannual timescales, there is no obvious relation between AMOC and DWBC. However,
on decadal timescales, our analysis indicates covariability between AMOC and DWBC. We
conclude that although caution should be exercised on interannual timescales, the DWBC
might be used as a proxy for long-term AMOC trends and possibly modulations of the
AMOC’s seasonal cycle. |
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