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Publication and Communication

Species distribution and oxygen isotope composition in modern planktic foraminifers in the Fram Strait (Arctic Ocean)

Authors

T. Pados R. Spielhagen.

 

Authors affiliation

GEOMAR


Event

4th Open Science Meeting

Goa, India

11-16 February 2013

 

POSTER

 

Abstract

Isotopic analyses and abundances of fossil foraminifera are common tools for paleoceanographic reconstructions. Oxygen isotopic (d18O) records of sediment cores provide information about variations in sea surface temperatures and salinities in the past, while the ratio between the abundances of different planktic foraminifer species refer to the hydrographic regime, e.g., distribution of water masses, water temperatures and the position of the summer sea ice margin. However, for a correct interpretation of the fossil data it is important to improve our understanding of the correlation between recent oceanic variability and the distribution/composition of shells of living foraminifera. For this purpose, water samples and planktic foramifers from plankton tows were studied along a transect across the Fram Strait (Arctic Ocean, 78°50’N, 5°W-8°E). Five depth intervals were sampled vertically between 500 m water depth and the sea surface by using a large-diameter multinet at 10 stations. This area is characterized by high oceanographic variability. In the western Fram Strait, the water column is strongly stratified, with cold, low-saline Arctic outflow waters of the East Greenland Current (EGC) in the upper 200 m and warmer, saline waters of Atlantic origin underneath. In the east the West Spitsbergen Current (WSC) carries Atlantic Water northwards, with a thin mixed layer on top. In the cold polar water masses of the EGC the polar species Neogloboquadrina pachyderma (sin.) clearly dominates the total assemblage, while the warm Atlantic water of the WSC yields higher abundances of Turborotalita quinqueloba. The multinet sampling results are also compared to the planktic foraminifer assemblages in sediment surface samples to investigate how well the planktic species distribution at the sea floor reflects the surface-near environments. The d18O values of the shells are compared to those from the water column. Results hold important information on preferred calcification depths of the foraminifers, which are variable in the different hydrographic regimes in the Fram Strait.

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