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| Titel |
A spatio-temporal reconstruction of sea surface temperature during Dansgaard-Oeschger events from model-data integration |
| VerfasserIn |
Mari F. Jensen, Aleksi Nummelin, Søren Borg Nielsen, Henrik Sadatzki, Evangeline Sessford, Hannah Kleppin, Bjørg Risebrobakken, Andreas Born |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127900
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| Publikation (Nr.) |
 EGU/EGU2016-7824.pdf |
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| Zusammenfassung |
| Proxy data suggests a large variability in the North Atlantic sea
surface temperature (SST) and sea ice cover during the Dansgaard
Oeschger (DO) events of the last glacial. However, the mechanisms behind
these changes are still debated. It is not clear whether the ocean
temperatures are controlled by forced changes in the northward ocean
heat transport or by local surface fluxes, or if, instead, the SST
changes can be explained by internal variability.
We address these questions by analyzing a full DO event using
proxy-surrogate reconstructions. This method provides a means to
extrapolate the temporally accurate information from scarce proxy
reconstructions with the spatial and physical consistency of climate
models. Model simulations are treated as a pool of possible ocean states
from which the closest match to the reconstructions, e.g., one model
year, is selected based on an objective cost function. The original
chronology of the model is replaced by that of the proxy data. Repeating
this algorithm for each proxy time step yields a comprehensive
four-dimensional dataset that is consistent with reconstructed data. In
addition, the solution also includes variables and locations for which
no reconstructions exist.
We show that by only using climate model data from the preindustrial
control simulations, we are able to reconstruct the SST variability in
the subpolar gyre region over the DO event. In the eastern Nordic Seas,
on the other hand, we lack the amplitude of the variations while
capturing the temporal pattern. Based on our analysis, we suggest that
the variability of the subpolar gyre during the analyzed DO event can be
explained by internal variability of the climate system alone. Further
research is needed to explain whether the lacking amplitude in the
Nordic Seas is due to the model deficiencies or if external forcing or
some feedback mechanisms could give rise to larger SST variability. |
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