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| Titel |
Holocene Atlantic Water temperature reconstruction in the Nordic Seas based on foraminiferal Mg/Ca ratios |
| VerfasserIn |
S. Aagaard-Sørensen, K. Husum, M. Hald, T. Marchitto, F. Godtliebsen |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065567
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| Zusammenfassung |
| In this study Mg/Ca-ratios have been used to reconstruct Holocene sea temperature variability
along the route of north flowing Atlantic Water in outer Andfjorden, Northern Norway
and on the West Spitsbergen Slope, eastern Fram Strait. The northbound flow of
warm and saline Atlantic Water to the Nordic seas is an integral part of Atlantic
Meridional Overturning Circulation (AMOC). Some of the Atlantic Water mass cools and
sinks forming part the North Atlantic Deep Water (NADW). Other parts of the
water mass are transported to the Arctic Ocean via the Fram Strait and the Barents
Sea.
The investigated study sites are both situated under the core of northwards flowing
Atlantic water. The record from the eastern Fram Strait is based on Mg/Ca-ratios measured
on the planktic foraminifer Neogloboquadrina pachyderma. The Andfjorden record is based
on Mg/Ca-ratios measured on the benthic foraminifer Melonis barleanus and stable isotopes
measured on the benthic foraminifer Cassidulina leavigata. In the Andfjorden bottom
water temperatures (BWTMg-Ca) show a strong influence from cold coastal and
melt waters during the deglaciation. In the early Holocene at 11,500 cal kyr B.P.
BWTMg-Ca increased markedly to ca. 11Ë C, when Atlantic Water influx into Andfjorden
increased. Both stable oxygen isotope and BWTMg-Ca values remained relatively
stable throughout the Holocene, but a significant BWTMg-Ca decrease of ~1Ë C
was observed around 3,500 cal yr B.P. In the eastern Fram Strait the reconstructed
sea surface temperatures (SSTMg-Ca) only show minor fluctuations during the
Late Glacial - Holocene transition. A temperature decline was initiated in the early
Holocene showing the lowest values around 2.8Ë C from ca. 5,200 to 2,700 cal
yr B.P. followed by increasing SSTMg-Ca towards the present. After 2,700 cal
yr B.P. sea surface temperatures gradually increased reaching the highest values
around 5Ë C at ca. 1,100 cal yr B.P. to present. The paleo records were governed by
different forcing factors like insolation, fluctuations of North Atlantic Deep Water
formation intensity, and changes of the atmospheric pressure systems changing the
northwards Atlantic Water advection. Furthermore, the calcification period and/or
the habitat depth of N. pachyderma may have changed through the studied time
interval influencing the reconstructions of SSTMg-Ca in the eastern Fram Strait. |
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