ALBERT

Description: Microfaunal assemblages of benthic foraminifera, ostracods, and tintinnids from two marine sediment cores retrieved from the Herschel Basin of the Canadian Beaufort Sea shelf document relationships with environmental parameters such as salinity, sea-ice cover, and turbulence. Cores YC18-HB-GC01 and PG2303-1 were collected at 18 and 32 m water depth, respectively. At these sites, sediment accumulation rates range between 0.6 and 1.7 cm yr–1 allowing a near-annual temporal resolution over the last 50 years. Multivariate analyses indicate that benthic foraminiferal assemblages respond primarily to food supply. Dissimilarities between the microfaunal assemblages of the two cores are mainly the result of bottom water salinity levels linked to water depth. High abundance of the benthic foraminiferal species Elphidium clavatum and occurrences of Elphidium bartletti point to varying, but relatively low, salinities at the shallow core site YC18-HB-GC01, which may be affected by variations in the summer halocline depth. Higher species diversity and more abundant Cassidulina reniforme and Stainforthia feylingi characterize the deeper core PG2303-1, which might reflect more stable conditions and higher bottom-water salinities throughout the studied time interval. The most important microfaunal shift of the last 50 years, observed in the shallower longer core YC18-HB-GC01, occurred at the turn of the 21st century. Prior to ∼2000 CE, the presence of Islandiella norcrossi indicates more stable and saline conditions. Since ∼2000 CE, increased abundances of Haynesina nivea and of the ciliate Tintinnopsis fimbriata suggest decreased salinity and increased turbidity. An increased abundance of Eoeponidella pulchella after ∼2000 CE suggests a concurrent increase in productivity in the last two decades. This shift is nearly synchronous with a decrease in mean summer sea-ice concentration, which can play an important role in bottom water stability on the shelf. Easterly winds can induce a reduction in the sea-ice cover, but also foster a westward spreading of the Mackenzie River plume and the upwelling of nutrient-rich Pacific waters onto the shelf. Both factors would explain the increased freshening and productivity of the Herschel Basin. The last two decades were also marked by a decrease in ostracod abundance that may relate to higher water turbidity. This study shows that combining information from benthic foraminifera, ostracods, and tintinnids provides a comprehensive insight into recent hydrographic/climatic changes in nearshore Arctic habitats, where productivity is critical for the food security of local communities.

Description: Due to the shortness of available records, the longterm patterns of climate variability in the Labrador Sea and Newfoundland region are not clear. Here, a diatom-based reconstruction of summer sea-surface temperature (SST) developed from Trinity Bay, Newfoundland, provides insight into variations of SST since 7.2 cal ka BP in the southwestern Labrador Sea. The results show that the Holocene Thermal Maximum (HTM) lasted until c. 5.2 cal ka BP, which was followed by a gradual cooling trend overprinted by centennial temperature fluctuations of 1-2°C.

Description: We carried out benthic foraminiferal assemblage-, stable isotope- and XRF analyses of a marine sediment core retrieved from the Northeast Greenland shelf (core DA17-NG-ST7-73), which provided a multiproxy reconstruction of Holocene paleoceanographic conditions. The results reveal significant variations in the water masses and thus, in the strength of the East Greenland Current over the last ca. 9.4 ka BP.

Description: Benthic foraminifera assemblage data for marine sediment core DA17-NG-ST03-039G retrieved in the Westwind Trough on the Northeast Greenland Shelf. The marine gravity core was collected during the NorthGreen2017 cruise on board the research vessel RV Dana. The data covers the period 13.3 to 3.9 cal ka BP. The benthic foraminifera assemblage data was carried out in order to reconstruct the oceanographic development on the Northeast Greenland shelf.

Description: Here, we present datasets of diatom abundance and a diatom-based sea surface temperature reconstruction from the Iceland Basin. The 419.5 cm long marine sediment core DA12-11/2-GC01 was recovered in September 2012 by the Danish R/V Dana using a gravity corer. The core was taken from a location at the northern edge of the Gardar Drift and the eastern edge of the Björn Drift in the Iceland Basin (61.36.536 °N, 20.42.164 °W) at a water depth of 2120 m. Diatoms were analysed at 5 cm intervals over the upper 2 m of core, representing the period 6100-0 cal years BP, with chronological constraints provided by 6 radiocarbon dates. Diatoms were analysed using standard procedures, including the identification and counting of a minimum of 300 diatom per sample, which allowed calculation of the percentage abundances of different species. These abundances were converted into estimates of sea surface temperature using the weight averaging partial least squares transfer function approach.