Holocene paleoceanography of the northern Barents Sea and variations of the northward heat transport by the Atlantic Ocean

Foraminiferal assemblages were studied in northern Barents Sea core ASV 880 along with oxygen and carbon isotope measurements in planktonic (N. pachyd erma sin.) and benthic (E. clavatum) species. AMS C-14 measurements perform ed on molluscs Yoldiella spp. show that this core provides a detailed and u ndisturbed record of Holocene climatic changes over the last 10000 calendar years. Surface and deep waters were very cold (<0<degrees>C) at the beginn ing of the Holocene. C. reniforme dominated the highly diverse benthic fora miniferal assemblage. From 10 to 7.8 cal. ka BP. a warming trend culminated in a temperature optimum, which developed between 7.8 and 6.8 cal. ka BP. During this optimum, the input of Atlantic water to the Barents Sea reached its maximum. The Atlantic water mass invaded the whole Franz Victoria Trou gh and was present from subsurface to the bottom. No bottom water, which wo uld form through rejection of brine during winter, was present at the core depth (388 m). The water stratification was therefore greatly reduced as co mpared to the present. An increase in percentage of I. helenae/norcrossi si points to Ion:: seasonal ice-free conditions. The temperature optimum ende d rather abruptly, with the return of cold polar waters into the trough wit hin a few centuries. This was accompanied by a dramatic reduction of the ab undance of C. reniforme. During the upper Holocene, the more opportunistic species E. clavtum became progressively dominant and the water column was m ore stratified. Deep water in Franz Victoria Trough contained a significant amount of cold Barents Sea bottom water as it does today, while subsurface water warmed progressively until about 3.7 cal. ka BP and reached temperat ures similar to those of today These long-term climatic changes were cut by several cold events of short duration, in particular one in the middle of the temperature optimum and another, which coincides most probably with the 8.2 ka BP cold event. Both long- and short-term climatic changes in the Ba rents Sea are associated with changes in the Bow of Atlantic waters and the oceanic conveyor belt.