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| Titel |
Monsoon variability in the northeastern Arabian Sea on orbital- and
millennial scale during the past 200,000 years |
| VerfasserIn |
Andreas Lückge, Jeroen Groeneveld, Stephan Steinke, Mahyar Mohtadi, Thomas Westerhold, Hartmut Schulz |
| 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 |
250126823
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| Publikation (Nr.) |
 EGU/EGU2016-6607.pdf |
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| Zusammenfassung |
| The Dansgaard-Oeschger oscillations and Heinrich events described in the Greenland ice
cores and in North Atlantic and Western Mediterranean sediments are also expressed in the
climate of the tropics, for example, as documented in Arabian Sea sediments. However, little
is known about these fluctuations beyond the reach of the Greenland ice cores. Here, we
present high-resolution geochemical, sedimentological as well as micropaleontological data
from two cores (SO130-283KL, 987m water depth and SO130-289KL, 571m) off the coast of
Pakistan, extending the monsoon record on orbital and millennial scales to the past 200,000
years.
The stable oxygen isotope record of the surface-dwelling planktonic foraminifer G. ruber
shows a strong correspondence to Greenland ice core δ18O, whereas the deepwater δ18O
signal of benthic foraminifera (U. peregrina and G. affinis) reflects patterns recorded in
ice cores from Antarctica. Strong shifts in benthic δ18O during stadials/Heinrich
events are interpreted to show frequent advances of oxygen-rich intermediate water
masses into the Arabian Sea originating from the southern ocean. Alkenone-derived
SSTs varied between 23 and 28˚ C. Highest temperatures were encountered during
interglacial MIS 5. Rapid SST changes of 2˚ C magnitude on millennial scale are
overlain by long-term SST fluctuations. Interstadials (of glacial phases) and the cold
phases of interglacials are characterized by sediments enriched in organic carbon (up
to 4 % TOC) whereas sediments with low TOC contents (< 1 % TOC) appear
during stadials and Heinrich events. Shifts at climate transitions, such as onsets of
interstadials, were coeval with changes in productivity-related and anoxia-indicating
proxies. Interstadial inorganic elemental data consistently show that enhanced fluxes
of terrestrial-derived sediments are paralleled by productivity maxima, and are
characterized by an increased fluvial contribution from the Indus River. In contrast,
stadials are characterized by an increased contribution of aeolian dust probably
from the Arabian Peninsula. Heinrich events are especially dry and dusty events,
indicating a dramatically weakened Indian summer monsoon and increased continental
aridity.
These results strengthen the evidence that North Atlantic temperature changes and shifts
on the hydrological cycle of the Indian monsoon system are closely coupled, and had
a massive impact on regional environmental conditions such as river discharge
and ocean margin anoxia. These shifts in the surface and sub-surface ocean were
modulated by changes in the supply of water masses from the southern hemisphere. |
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