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| Titel |
Southern Caribbean Sea temperature and salinity variability since the mid-Holocene from monthly resolved coral records |
| VerfasserIn |
Thomas Felis, Cyril Giry, Martin Kölling, Denis Scholz, Wei Wei, Gerrit Lohmann, Sander Scheffers |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074836
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| Zusammenfassung |
| In the tropical Atlantic, proxy reconstructions of Holocene sea surface temperature and
salinity that resolve seasonality and interannual to decadal variability are sparse.
However, ocean-atmosphere interactions on these timescales play a critical role for
climate extremes such as droughts, floods and hurricanes. Consequently, a better
understanding of the natural range of sea surface variability on these timescales
is important for projections of future tropical Atlantic climate change. Here we
present monthly resolved reconstructions of sea surface temperature (SST) and
δ18Oseawater (used as proxy for sea surface salinity, SSS) in the southern Caribbean Sea
for snapshots throughout the mid- to late Holocene, derived from Sr/Ca and δ18O
analyses of fossil shallow-water corals (Diploria strigosa) from Bonaire (Netherlands
Antilles). The corals were dated by the 230Th/U-method and provide a total of
~300 years of record, with individual time windows reaching up to 68 years in
length.
Our coral records indicate that mid- to late Holocene SST and SSS were characterized by
persistent quasi-biennial and prominent interannual to multidecadal variability. However, the
amplitude of variability on individual timescales has varied over the last 6200 years.
We find that on interannual to multidecadal timescales, warmer conditions were
accompanied by more saline conditions at the sea surface, and vice versa. Potential forcing
mechanisms of this observed pattern are discussed, including the wind-induced
advection of surface waters from the South and the variations in the strength of the
Atlantic Meridional Overturning Circulation. Compared to the late Holocene, SST
variability on inter- to multidecadal timescales was more pronounced during the mid-
Holocene, and accompanied by enhanced SSS variability. Moreover, an increased
amplitude of the SSS annual cycle is reconstructed for the mid- Holocene, very likely
resulting from increased summer precipitation at that time, which is consistent
with our climate model simulations (COSMOS). A time interval of anomalous sea
surface conditions in the southern Caribbean is indicated at 2350 years ago, which is
characterized by enhanced interannual SST variability at typical ENSO periods, an
increased amplitude of the SST annual cycle, and a reversal of the SSS annual
cycle.
In summary, whereas the amplitude of the reconstructed interannual to multidecadal SST
variability was quite variable, the amplitude of the SST annual cycle was within
the modern range during most of the coral-based snapshots that cover a total of
~300 years during the last 6200 years. Exceptions include a slightly increased SST
seasonality at 6200 years ago, which we attribute to insolation forcing on orbital
timescales, consistent with our model simulations, and a significantly increased SST
seasonality at 2350 years ago, which we attribute to internal dynamics of the climate
system. This work is a contribution to the DFG Programme INTERDYNAMIC. |
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