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| Titel |
Variability of the North Atlantic during Past Climate Change: Inference from Scarce and Inaccurate Data |
| VerfasserIn |
Olivier Marchal, Claire Waelbroeck, Alain Colin de Verdière |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106900
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| Publikation (Nr.) |
 EGU/EGU2015-6580.pdf |
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| Zusammenfassung |
| The role of North Atlantic variability in climate change remains poorly understood due in
large part to the limited span of instrumental records. This situation invites researchers to
consult other sources of information, in particular records of sea surface temperature (SST)
estimated from the analysis of marine sediments. Interpreting SST records from deep-sea
sediment cores, however, is a delicate problem, as the SST estimates are generally scarce,
inaccurate, and sometimes inconsistent. Here we discuss the interpretation of a small number
of North Atlantic SST records characterized by (generally) centennial resolution and
spanning the past 15,000 years, i.e., part of the last glacial-interglacial transition and episodes
of more abrupt climate change, such as the Younger Dryas. An attempt is made
to infer the time-evolving SST field in the North Atlantic from the quantitative
combination of the SST records with an advective mixed layer model using methods of
optimal estimation theory (an extended Kalman filter and a fixed-interval smoother).
The error covariance of the time-evolving SST field is evaluated from the model
dynamics, the reduced availability and accuracy of the SST estimates, and estimates
of the model errors. We find that the climatologic position of the 10°C surface
isotherm, which today coincides approximately with the North Atlantic Current
and the Subpolar Front, pivoted recurrently around a region near the Tail of the
Grand Banks: during cold climate intervals, the isotherm assumed a more zonal
and southern position compared to today, whereas during warm climate intervals
it was generally oriented SW-NE, such as today. In our presentation, emphasis
will be placed on the statistical and oceanographic significance of this interesting
result. |
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