Paleaoceanographic Changes in Disko Bugt Area in Relation With Human Settlements During the Holocene

English Abstract:

Palynological and isotopic analyses of a sediment core raised off Disko Bugt (West Greenland) were undertaken in order to document Holocene paleoceanographical changes in the eastern Baffin Bay. The Modern analogue Technique (MAT) applied to dinocyst assemblages provided information on paleo sea-surface conditions (temperature, salinity, sea-ice cover and productivity) whereas isotopic analyses of benthic foraminifera aimed at documenting the "deep" water mass at the site. The paleoceanographic information we obtained is compared with archeological data from the Disko area as compiled by JF Jensen et al. (Copenhagen University Archaeological Notes, 1999).

From ~ 10 to ~ 7.3 ka, important discharge of ice and meltwaters from the Greenland ice sheet, mostly through the Jakobshavn Isbrae, resulted in harsh conditions with dense sea-ice cover, low temperature and low pelagic and benthic productivity. Postglacial conditions settled at about 7.3 ka as indicated by a sharp increase in dinocyst diversity and abundance, which corresponds to increase in summer temperatures. Optimal conditions were finally achieved by about 6 ka, i.e. before the first human occupancy dated at about 4.5 ka. The mid- to late Holocene dinocyst data suggest a slight cooling with increased sea ice cover at ~ 4.2-4.0 ka followed by a slight warming, which matches maximum occurrence of Saqqaq people artefacts in Disko area. Sea-surface temperature continued to increase in summer until about 1.8 ka, when a pronounced cooling was accompanied by increased seasonal sea ice cover and salinity, together with a decrease in productivity. The event marked by harsh conditions in surface waters spanned from about 1.8 to 1 ka. It is consistent with a slight increase in δ¹⁸O-values in benthic foraminifers at about 2.1-1.1 ka, which also indicate a cooling in subsurface waters and/or lesser meltwater fluxes. This regional event coincides with the main decline in the number of paleo-Eskimo occupation sites in the Disko area. On this basis it might be hypothesized that rough climate conditions and productivity drop contributed together to the regional decline in paleo-Eskimo population.