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Publication and Communication

*Coccolith-Carbonate Sedimentation in the Northern North Atlantic : an Holocene Perspective


Jacques Giraudeau1, Jennifer Garcia2, Christian Valdemar Dylmer1, Katrine Husum3, Kirstin Werner4, Robert F Spielhagen4, Juliane Müller5, Matthias Moros6, Bjxrg Risebrobakken7

Authors Affiliation

1. EPOC, University of Bordeaux -CNRS, Talence, France.
2. EA BIAF, University of Angers, Angers, France.
3. Department of Geology, University of Tromsø, Tromsø, Norway.
4. IFM GEOMAR, Leibniz Institute of Marine Sciences, Kiel, Germany.
5. Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
6. Leibniz Institute for Baltic Sea Research, Rostock, Germany.
7. Bjerknes Center for Climate Research, Bergen, Norway.


AGU Fall Meeting 2011

San Francisco, USA

5-8 December 2011




High concentrations of carbonate in surface sediments of the Nordic Seas are generally
related to warm Atlantic Water (AW) inflow. This relationship was recently used to infer the Holocene dynamics of Atlantic-derived water off North-West Iceland (Giraudeau et al, 2010; QSR vol. 29) following suggestions that carbonate production in the vicinity of Denmark Strait is tightly linked with inputs of warm, nutrient-rich Irminger Current waters. The present study aims at testing this assumption in the two main passageways of AW to the Arctic Ocean: Fram Strait and the Barents Sea, with a focus on a high resolution Holocene sediment record collected off western Svalbard. Our datasets on extant coccolithophores, as well as estimates of coccolith-carbonate contents within the studied marine cores suggest that sedimentation of calcium carbonate in the northernmost North Atlantic essentially reflects production rates of coccolithophores, and that sedimentation of their fossil remains is driving to a high extent the Holocene variations in net CaCO3 accumulation in Fram Strait and the SW Barents Sea. Our coccolith-based proxy records are indicative of a complex regional dynamics of Holocene surface water changes in these two regions. With the exception of a ca. 2 000 years delayed recovery of surface AW influence to the SW Barents Sea in the early Holocene, both regions experienced the same history of surface water temperature changes until ca. 3 000 cal.yrs BP. A Holocene sea-surface thermal optimum is clearly recognized in both regions during the 8 000 to 7 000 cal. yrs BP interval, followed by a large scale surface cooling triggered by reduced poleward inflow of AW across the Iceland-Scotland Ridge. A decoupling in the pattern of coccolith-carbonate sedimentation between Fram Strait and the SW Barents Sea characterizes the late Holocene. While near continuous surface water warming impacted the southern Barents Sea throughout the last 3 000 years, the eastern Fram Strait was affected by the settling, during maximum AW inflow to the Arctic Ocean, of a strong stratification separating a fresh, sea-ice rich surface mixed-layer of polar origin from an AW-derived poleward water mass.

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