A multiproxy reconstruction of the evolution of deep and surface waters in the subarctic Nordic seas over the last 30,000yr

Bauch, Henning A., Erlenkeuser, Helmut, Spielhagen, Robert F., Struck, Ulrich, Matthiessen, Jens, Thiede, Jörn and Heinemeier, Jan (2001) A multiproxy reconstruction of the evolution of deep and surface waters in the subarctic Nordic seas over the last 30,000yr Quaternary Science Reviews, 20 (4). pp. 659-678. DOI 10.1016/S0277-3791(00)00098-6.

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Abstract

On the basis of various lithological, mircopaleontological and isotopic proxy records covering the last 30,000 calendar years (cal kyr) the paleoenvironmental evolution of the deep and surface water circulation in the subarctic Nordic seas was reconstructed for a climate interval characterized by intensive ice-sheet growth and subsequent decay on the surrounding land masses. The data reveal considerable temporal changes in the type of thermohaline circulation. Open-water convection prevailed in the early record, providing moisture for the Fennoscandian-Barents ice sheets to grow until they reached the shelf break at ∼26 cal. kyr and started to deliver high amounts of ice-rafted debris (IRD) into the ocean via melting icebergs. Low epibenthic δ18O values and small-sized subpolar foraminifera observed after 26 cal. kyr may implicate that advection of Atlantic water into the Nordic seas occurred at the subsurface until 15 cal. kyr. Although modern-like surface and deep-water conditions first developed at ∼13.5 cal. kyr, thermohaline circulation remained unstable, switching between a subsurface and surface advection of Atlantic water until 10 cal. kyr when IRD deposition and major input of meltwater ceased. During this time, two depletions in epibenthic δ13C are recognized just before and after the Younger Dryas indicating a notable reduction in convectional processes. Despite an intermittent cooling at ∼8 cal. kyr, warmest surface conditions existed in the central Nordic seas between 10 and 6 cal. kyr. However, already after 7 cal. kyr the present day situation gradually evolved, verified by a strong water mass exchange with the Arctic Ocean and an intensifying deep convection as well as surface temperature decrease in the central Nordic seas. This process led to the development of the modern distribution of water masses and associated oceanographic fronts after 5 cal. kyr and, eventually, to today's steep east–west surface temperature gradient. The time discrepancy between intensive vertical convection after 5 cal. kyr but warmest surface temperatures already between 10 and 6 cal. kyr strongly implicates that widespread postglacial surface warming in the Nordic seas was not directly linked to the rates in deep-water formation.

Document Type: Article
Keywords: Nordic Seas; Arctic Ocean; Atlantic Ocean; Water circulation; Water mass exchange; Paleoceanography
Research affiliation: AWI
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
DOI etc.: 10.1016/S0277-3791(00)00098-6
ISSN: 0277-3791
Projects: Paläoklimaprojekt
Date Deposited: 04 Mar 2015 11:35
Last Modified: 19 Sep 2016 09:41
URI: http://eprints.uni-kiel.de/id/eprint/27841

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