Arctic Ocean iceberg drift patterns and paleoenvironmental change in the last 50 kyr reconstructed from an Alpha Ridge to Gakkel Ridge transect.

Spielhagen, Robert, Nørgaard-Pedersen, Niels and Vehlow, Anna (2012) Arctic Ocean iceberg drift patterns and paleoenvironmental change in the last 50 kyr reconstructed from an Alpha Ridge to Gakkel Ridge transect. [Talk] In: APEX IV, Arctic Palaeoclimate and its Extremes, International Conference and Workshop. , 15.05.-18.05.2012, Oulanka, Finland . APEX VI, Palaeoclimate and its Extremes : international conference and workshop, Oulanka, Finland, 15-18 May 2012. ; p. 87 .

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Abstract

The Arctic Ocean has undergone profound changes in the last ca. 50 kyr, reaching from a dense sea ice cover with large numbers of icebergs during the mid-Weichselian glaciation (MWG, >45 ka) to a perennial sea ice cover with seasonally open leads in the Holocene. During the main glacial phases (MWG and last glacial maximum (ca. 20 ka)), large parts of the surrounding continents were covered by ice sheets which discharged icebergs to the ocean, leaving traces in the form of ice-rafted debris (IRD) in the bottom sediments. Different lithologies in the source areas of the icebergs allow to reconstruct the pathways of the ice and thus the large-scale drift pattern of the oceanic ice cover. Microfossils and geochemical proxies give evidence of other parameters of the surface-near water masses and their spatial and temporal variability. We use a multiproxy data set from sediment cores obtained between the Alpha (130-160°W) and Gakkel (30-60°E) ridges to reconstruct the paleoenvironment in the central Arctic with emphasis on the intervals with extensive continental glaciations. Sedimentation rates were generally low (1 cm/kyr or less) with the exception of the MWG with several cm/kyr. Coarse fraction content (IRD and microfossils) in sediments from both glaciation intervals is increasing towards the Alpha Ridge, revealing a stronger influence (iceberg discharge) of the North American Arctic ice sheet if compared to the northern Eurasian ice sheet. Planktic foraminifer occurrences in Alpha Ridge sediments from the MWG indicate that seasonally open waters were present occasionally and may have allowed higher melt rates than in the Eurasian subbasin. The paleoenvironmantal picture for the LGM is more ambiguous because of extremely low sedimentation rates or even an interval of non-sedimentation. However, it seems likely that the eastern part of the Eurasian Basin was largely free of icebergs for a few thousand years during the LGM. The different dominating lithologies of IRD found in the analyzed sediment cores point to different regional sources of icebergs for the last 50 kyr and allow to trace the boundary between the ice drift systems in the Amerasian and Eurasian subbasins through time. The MWG sediments at all sites show a minimum in carbonate/dolomite contents, indicating a more southward position of the Beaufort Gyre than today. Increasing proportions of carbonate/dolomite thereafter indicate a continuous iceberg export from the North American Arctic in the last 50 ky.

Document Type: Conference or Workshop Item (Talk)
Keywords: Palaeoclimatology; glaciology; Arctic Ocean
Research affiliation: AWI
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Open Access Journal?: Yes
Projects: Polynya, Laptev Sea System
Date Deposited: 22 Dec 2014 10:59
Last Modified: 22 Dec 2014 10:59
URI: http://oceanrep.geomar.de/id/eprint/26628

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