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Steffen Aagaard-Sørensen, University of Tromsø (Norway)
Katrine Husum, University of Tromsø (Norway)
Morten Hald, University of Tromsø (Norway)
Jochen Knies, Geological Survey of Norway (Norway)
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This study aims to examine the lateglacial-early Holocene variability of the northward flowing North Atlantic Current (NAC) penetrating into the northern North Atlantic. The meridional transport of warm and saline Atlantic Water with NAC into the North Atlantic region has previously been studied showing a time transgressive onset of the Holocene thermal maximum along a north to south transect. This study aims to elucidate the zonal component of this meridional transport. We have investigated a sediment core from Ingoydjupet, at 409 m water depth SW Barents Sea. This location is at present influenced by Atlantic Water from the zonal branch of NAC, the North Cape Current (NCaC), and a fresher water mass from the Norwegian Coastal Current (NCC). Both currents are important in the meridional overturning circulation system of the North Atlantic. AMS 14C dates indicate that the time resolution is at a centennial scale, giving the potential for studying the paleoceanographic changes with a high temporal resolution. The core has been analyzed for its faunal distribution of planktonic foraminifera in the 100 μm fraction and for δ13C and δ18O isotopes in both benthic and planktonic foraminifera. Furthermore, a range of chemical and physical analyses have been carried out on the bulk sediment including MSCL, grain size distribution, TOC, CaCO3, δ13C and biogenic silica and finally IRD counts have been carried out. Between 12.700-12.200 cal yr BP a high flux of planktonic foraminifera occurred. This period is totally dominated by the species Neogloboquadrina pachyderma (sin) pointing towards very chilled surface water conditions during a period of seasonally open waters. This interval was probably influenced by icebergs as indicated by relatively high amounts of IRD. The TOC and CaCO3 content of the sediment also points to relatively high primary production during this period. From ca 12.200-11.000 cal yr BP the sediment is virtually barren as very few planktonic and benthic foramifera are found. This low productivity is further emphasized by low TOC and CaCO3 content. From ca. 11.000-7.000 cal yr BP the foraminiferal fauna shows an overall dominance by Turborotalita quinqueloba. This dominance indicates a strong continuous eastward influx of Atlantic Water into the SW Barents Sea and a close proximity to the Arctic Front that separates the cold Arctic and warm Atlantic waters. This early Holocene warming occurred during enhanced summer insolation. A period of relatively colder surface water conditions is indicated by an increase of the cold water species N. pachyderma (sin) from ca. 8.600-8.100 cal yr BP. Taking the uncertainty in the age model into account, this cooling event relates to the 8.2 ka cold event, which has previously been recognized in the North Atlantic region, including the Barents Sea. The benthic and planktonic δ13C and δ18O isotope values show a parallel fluctuation pattern signalling a vertical mixing of the water masses.
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