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| Titel |
Holocene evolution of water masses and sea ice on the western Barents Sea margin: a multiproxy review |
| VerfasserIn |
Katrine Husum, Sarah Berben, Patricia Cabedo-Sanz, Christian Dylmer, Diane Groot, Steffen Aagaard Sørensen, Simon Belt, Jacques Giraudeau, Fred Godtliebsen |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089729
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| Publikation (Nr.) |
 EGU/EGU2014-3939.pdf |
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| Zusammenfassung |
| The present climate in the Arctic shows signs of rapid change with decreasing sea ice cover
and increasing temperature of the Atlantic Water. The implications of this warming are
highly uncertain; hence it is crucial to obtain longer records of climate changes in
the past to assess the natural limits of Arctic climate. Consequently, in order to
investigate natural rapid ocean changes on longer time scales, robust reconstructions of
past surface water masses and sea ice need to be carried out. The aim of the study
is to elucidate the limits of different water mass and sea ice conditions using a
multi-proxy-based approach. The study site is situated close to the modern day marginal ice
zone and is influenced by Atlantic and Arctic waters. A gravity core from the western
Barents Sea margin has been investigated using benthic and planktic foraminifera,
stable isotopes (δ18O, δ13C), coccoliths and biomarkers (IP25, brassicasterol and
24-methylenecholesterol). A depth-age model was developed using eight radiocarbon dates,
and showed sediment accumulation rates from ca. 3 cm/kyr – 25 cm/kyr. During
the Early Holocene, the bottom and subsurface water mass temperature proxies
show an overall warming of 2.5 - 3°C from ca. 11.700 – 9.400 cal. yr BP and ca.
11.700 – 10.600 cal. yr BP, respectively. Additionally, the sea ice proxies show a
decrease of seasonal sea ice throughout the period. Coccolith ratios (surface water
proxy) indicate a continuous influence of Atlantic Water, although distributions may
also be caused by melt water and a strong stratification of the upper surface water
masses during this time interval. During the Mid – Late Holocene, the temperature of
bottom and subsurface water masses remain relatively stable from ca. 9.400 and
10.600 cal. yr BP until 1.500 cal. yr BP. The benthic and planktic δ18O values reflect
slightly decreasing temperatures consistent with the decreasing insolation. The
coccolith ratio reflects the fluctuations of the Arctic Front and the variations of
Arctic and Atlantic Water in the surface water during this time interval. The relative
abundance of the coccolith G. muellerae also indicates a sustained flow of Atlantic
Water from ca. 9.500 – 5.500 cal. yr BP. Seasonal sea ice disappears after 8.500 cal.
yr BP, but re-appears in intermittent intervals from ca. 7.500 - 5.000 cal. yr BP.
After ca. 1.100 cal. yr BP, all proxies generally fluctuate, reflecting more unstable
oceanographic conditions. The planktic foraminiferal fauna indicates slightly lower
salinities in the subsurface water masses and the benthic foraminiferal fauna also
indicates more unstable conditions. The coccolith record indicates an increased
inflow of Atlantic water after 1.500 cal. yr BP. Seasonal sea ice is again present from
1.500 cal. yr BP towards the present. These apparent contradicting findings after 1.5
ka BP may reflect a decoupling of the water masses and/or different forcings of
ocean currents and atmospheric circulation. This study illustrates well the different
signatures of biological-based proxies and how integrated multi-proxy studies enable a
more comprehensive reconstruction of paleoceanographic and climatic evolution. |
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