Brice, Camille; de Vernal, Anne; Francus, Pierre; Forwick, Matthias et Nam, Seung-Il
(2022).
« Millennial-scale oscillations and an environmental regime shift around the Middle to Late Holocene transition in the North Atlantic region based on a multiproxy record from Isfjorden, West Spitsbergen ».
Boreas, 12602, pp. 1-18.
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Résumé
Palynological and sedimentological analysis from sediment core HH16-1205-GC retrieved fom central Isfjorden, West Spitsbergen, spanning the last 7 ka, revealed overall cooling with a significant climate shift between 4.4 and 3.8 ka, in addition to millennial-scale oscillations. Sea-surface reconstruction from dinocyst assemblages indicates a decrease in summer sea-surface temperature, from 2.5°C to 1.5°C, and primary productivity, from 750 to 650 gC·m-²·a-1 over the last 7000 years. From around 6.8 to 5.8 cal. ka BP, the sedimentological and palynological data suggest predominant sediment supply from the inner part of the fjord, ice rafting, dense sea-ice cover, strongly stratified waters, and high primary productivity. The interval from 4.4 to 3.8 ka BP is marked by a layer of coarser material and a significant decrease in grain size mode. The geochemical data suggest evolving bottom water mass conditions and sedimentary regime, while palynological data reveal changes in sea surface salinities. Our geochemical data show large-amplitude fluctuations after 2.0 cal. ka BP, while an increase of Impagidinium pallidum and Spiniferites elongatus from 2.0 to 1.2 cal. ka BP suggests enhanced Atlantic Water inflow. The dinocyst-based reconstructions also revealed large-amplitude millennial fluctuations in sea-ice cover, summer sea-surface temperature, and salinity. Wavelet analysis and cross-wavelet analysis on K/Ti ratio coupled with sea-ice estimates confirmed a strong signal with a periodicity of 1100 to 1500-years.
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