A Preliminary Study On The Holocene Palaeoenvironmental Changes In West Greenland

Being located in the Arctic and North Atlantic region, West Greenland is sensitive to global climate changes. Thus, studies on global climate change here are of vital importance.As fjords are connected to the open seas, they allow exchanges of mass and energy of marine and terrestrial environments, thus often providing high-resolution sedimentary records that document the interaction of marine and terrestrial processes. Fjord records from high latitudes, where global change may be amplified rapidly, have the potential to offer valuable palaeoenvironmental information not only on local climatic and hydrographic changes but also on large-scale oceanographic and atmospheric oscillations. However, compared with other parts of the North Atlantic, only a few marine records on the Holocene have been studied from West Greenland. The sediment samples of this study are all from West Greenland, which may provide new records on the Holocene environmental changes in this area.The sediment samples in this study are from core DA04-41P collected in Ameralik Fjord, core DA00-06T and some surface samples retrieved from Disko Bugt. A total of 63 samples were analyzed for diatom content in core DA04-41P and totally 106 taxa were found. Totally 27 samples and 81 diatom taxa were studied from core DA00-06T, while 18 samples and 78 taxa were analyzed in surface samples.The diatom records, together with other proxies, such as ¹⁴C dating, lithology, foraminiferal analysis, XRF and magnetic susceptibility, reveal the Holocene environmental changes in West Greenland. The record from core DA04-41P covers the period of 8800-3600 cal. yr BP, while core DA00-06T reflects the changes from 1200 cal. yr BP to modern time. The surface samples show the relationship between the diatom species and the modern environmental factors, facilitating the implications of palaeoenvironment by diatom fossils.In core DA04-41P, a minor episode of cold surface-water conditions is found at ca. 8000-7800 cal. yr BP. This may be due to the local conditions in the fjord or linked to the culmination of a strong melt-water outflow rather than reflecting the widespread the North Atlantic (8200 cal. yr BP) cooling event. Warming of surface-water condition from 7800 to 7100 cal. yr BP, 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. A major sedimentary change with a hiatus between 6800 and 4500 cal. yr BP prevents a reconstruction of mid-Holocene paleoceanograpy. The final and less prominent part of the HTM is found after 4400 cal. yr BP.In core DA0-06T, a relatively warm period influenced by strong West Greenland Current (1200-800 cal. yr BP) and a climate cooling from 800 cal. yr BP are revealed by diatom records. It remains unclear whether this warm period is corresponding to the Medieval Warm Period, because of the contradictory results in the same area. The subsequent cooling record is found in a large amount of studies from West Greenland and the North Atlantic, which may be regard as the Little Ice Age.The findings of the early and late Holocene climate development of West Greenland show no clear NAO-type signal, which was suggested by other earlier studies.This study shows that sedimentary records from West Greenland fjords, which are controlled by both marine and land processes, provide valuable palaeoenvironment information confirming a linkage between local and large-scale North Atlantic oceanographic and atmospheric oscillations.