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Palynological and sedimentological analyses were performed on the sediment core HH16‐1205‐GC retrieved from the central Isfjorden, West Spitsbergen. The sequence, which spans the last 7000 years, revealed an overall cooling trend with an important climate shift between 4.4 and 3.8 cal. ka BP, in addition to millennial‐scale oscillations. Sea‐surface reconstruction from dinocyst assemblages indicates a decrease in summer sea‐surface temperature, from 2.5 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 a predominant sediment supply from the inner part of the fjord, ice rafting, dense sea ice cover, strongly stratified water masses and high primary productivity. The interval from 4.4 to 3.8 cal. ka BP is marked by a layer of coarser material and a significant decrease in the grain‐size mode. Our geochemical data show large‐amplitude fluctuations after 2.0 cal. ka BP, while an increase in the dinocysts Impagidinium pallidum and Spiniferites elongatus from 2.0 to 1.2 cal. ka BP suggests enhanced Atlantic Water inflow. The dinocyst‐based reconstructions also reveal 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 confirm a strong signal with a periodicity of 1200–1500 years. [ABSTRACT FROM AUTHOR]

Postglacial changes in sea-surface conditions, including sea-ice cover, summer temperature, salinity, and productivity were reconstructed from the analyses of dinocyst assemblages in core S2528 collected in the northwestern Barents Sea. The results show glaciomarine-type conditions until about 11,300 ± 300 cal yr BP and limited influence of Atlantic water at the surface into the Barents Sea possibly due to the proximity of the Svalbard-Barents Sea ice sheet. This was followed by a transitional period generally characterized by cold conditions with dense sea-ice cover and low-salinity pulses likely related to episodic freshwater or meltwater discharge, which lasted until 8700 ± 700 cal yr BP. The onset of "interglacial" conditions in surface waters was marked by a major change in dinocyst assemblages, from dominant heterotrophic to dominant phototrophic taxa. Until 4100 ± 150 cal yr BP, however, sea-surface conditions remained cold, while sea-surface salinity and sea-ice cover recorded large amplitude variations. By -4000 cal yr BP optimum sea-surface temperature of up to 4°C in summer and maximum salinity of -34 psu suggest enhanced influence of Atlantic water, and productivity reached up to 150 gC/m²/yr. After 2200 ± 1300 cal yr BP, a distinct cooling trend accompanied by sea-ice spreading characterized surfacewaters. Hence, during the Holocene, with exception of an interval spanning about 4000 to 2000 cal yr BP, the northern Barents Sea experienced harsh environments, relatively low productivity, and unstable conditions probably unsuitable for human settlements. [ABSTRACT FROM AUTHOR]

The sedimentary records of Arctic fjords can provide insights on the impact of natural variations and anthropogenic forcing on the glacier ice dynamics, notably in relation to ocean waters changes. The fjords of western Svalbard are characterized by large temperature and salinity gradients, which are determined by the relative inflow of warm and saline North Atlantic waters and the cold freshwater discharge from continental glacier runoff waters and Arctic coastal waters. In this context, the ice margin dynamics of the last ~7000 years was studied from a core collected in central Isfjorden, W. Spitsbergen, where rapid sediment accumulation rates allowed high temporal resolution recordings. In this core, dinocyst assemblages provide indication on oceanographical conditions whereas the physical and geochemical properties of sediments relate to the dynamics of the terminal glaciers in the fjord. The results show high frequency variations in sea surface conditions reconstructions throughout the sequence, in particular in temperature (SST), and sea ice cover. However, a general trend toward a cooling is observed in all conditions, SST decreases from 2,5 to 1,5°C and primary productivity decreases from 750 to 650 gC/m²/year. Although the reconstructions show noisy variations, smooth curve reveals medium frequency suggesting millennial oscillations in sea ice cover, summer temperature and salinity. Near the bottom of the core, an interval encompassing from 7000 to 6500 cal. yrs BP is marked by a peak of abundance of Pentapharsodinium dalei, which reflects particularly high primary productivity. This peak corresponds to high calcium and strontium content which would come from glacial erosion from the inner part of the fjord. The reconstructions suggest that this interval was also marked by low SSS of 31 psu and high sea ice cover of 8 months/year. At ~4000 cal. yrs BP, the grain size distribution and manganese content suggest a change in sedimentary regime, related to a glacial environment. This change is followed at ~3600 cal. yrs BP by an increase in sea ice cover of 2 months/yr. At ~2000 cal. yrs BP, the geochemical and dinocyst records are characterized by large amplitude variations in all elements as well as an increase in Impagidinium pallidum and Spiniferites elongatus, suggesting changes in the Atlantic water input. Principal component analysis made on sea surface conditions and geochemical data shows that sea ice cover and calcium and strontium are covariant. This would indicate a direct correlation between sea surface conditions and glacial activity since these elements come from glacial erosion. [ABSTRACT FROM AUTHOR]