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| Titel |
Centennial scale variability in Scotia Sea surface and bottom water properties during the Late Holocene |
| VerfasserIn |
Allyson Tessin, Ulysses Ninnemann, Helga Flesche Kleiven |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052411
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| Zusammenfassung |
| The Southern Ocean has been one of the most rapidly warming regions of the world. Yet
sources of these trends and the relative roles of anthropogenic and natural influences, as well
as their potential impacts on ocean circulation remain debated—due, in part, to the
brevity and scarcity of appropriate instrumental records. Records characterizing
long-term natural climate variability are, therefore, necessary to contextualize recent
trends and to understand their potential impacts on the Southern Ocean and its
circulation.
Here we use a radiocarbon dated, 25 cm long sediment core (Multicore GS08-151-02MC,
53Ë 31.81’S, 44Ë 42.14’ W, 2750 m) to infer near surface polar variance over the last 3500
years. We use an oxygen isotope record of planktonic foraminifera (N. Pachyderma s.) to
reconstruct surface ocean physical properties and infer changes in the large-scale oceanic and
atmospheric systems that influence them. Our initial N. Pachyderma (s.) δ18O results indicate
a cooling trend in polar near surface waters over the last several millennia overlain by
frequent variability of up to 1Ë C (or 0.71 PSU). This centennial scale variability is of the
same magnitude as recent warming but occurred over much longer timescales. To
further elucidate the relationship between natural climate variability and deep ocean
circulation, we compare near surface and bottom water property records within our
core—allowing us to unequivocally resolve the magnitude and timing of deep ocean changes
relative to surface property variability. Our initial Uvigerina δ18O results show that
bottom water property variability is of similar magnitude to that in the near surface
record indicating that there has been significant natural variability in Southern Ocean
deep water on centennial timescales. The existence of significant centennial scale
variability in both surface and deep Southern Ocean physical properties supports the
hypothesis that ocean property anomalies in this region play a critical role in the genesis
of centennial scale variability in climate and meridional overturning circulation. |
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