A diatom-based reconstruction of Early Holocene hydrographic and climatic change in a southwest Greenland fjord

Abstract

A diatom-based reconstruction of surface-water paleoclimatic and paleoceanographic changes in Ameralik Fjord, southwest Greenland, is presented for the Holocene interval 8800 to 3600 cal yrs B.P. A minor episode of cold surface-water conditions is found at ca. 8000–7800 cal yrs B.P. This may be due to the local conditions in the fjord and linked to the culmination of a strong melt-water outflow rather than reflecting the widespread North Atlantic (8.2 ka) cooling event. Warming of surface-water condition from 7800 to 7100 cal yrs B.P., probably corresponding to the early and warmest part of the Holocene Thermal Maximum (HTM) in this region, is reflected in the diatom assemblages and supported by other proxies. The West Greenland Current (WGC) influences the fjord strongly during this interval, indicating enhanced advection of Atlantic water-masses derived from the Irminger Current (IC). A major sedimentary change with a hiatus between 6800 and 4400 cal yrs B.P. prevents a reconstruction of mid-Holocene paleoceanograpy. The final and less prominent part of the HTM is found after 4400 cal yrs B.P. Previous studies from the same site have shown this final stage of the HTM to end at 3200 cal yrs B.P. with the onset of the ‘Neoglaciation’. Our study provides further evidence that the marine sedimentary record from West Greenland fjords yields paleoenvironmental information reflecting a significant link between local and large scale North Atlantic oceanographic and climatic changes.