Holocene climatic variations and previous glaciation of the shelf
The primary scientific focus of the project is directed towards marine geological studies of three fjord and shelf areas in West Greenland. The goal is to establish an overall picture of the differences and similarities in the post-glacial development of these three areas, seen in a geological and climatic perspective. The project thus aims to reconstruct the changes in the circulation patterns in the Greenlandic fjords and shelf areas, and to relate these changes to Holocene climate changes. Special emphasis will be placed on reconstructing the freshwater melting of the Greenland Inland Ice, the extent of sea ice and the occurrence of icebergs off South and West Greenland, as well as the possible relationships and connections with the North Atlantic Thermohaline Circulation system, including the apparent counter-phase between the climatic conditions of South Greenland and Northwestern Europe.
The freshwater balance in polar areas is an important parameter that affects the global climate system, including the conditions in the Labrador Sea and the Davis Strait. Generally, an increase in freshwater inflow will favour the formation of sea ice in the Labrador Sea and lead to a reduction in deep-water convection, which, according to the climate models, may eventually lead to a reduction in the North Atlantic circulation and thus a colder climate in the North Atlantic region. Micropalaeontological studies of marine sediment cores will give a detailed picture of the late Holocene climate changes, including changes in the influence of the dominant North Atlantic Ocean currents. Special focus will be directed towards the West Greenland current system in the coastal areas of West Greenland, storm frequencies and variations in the quantity and occurrence of sea and fjord ice. Extensive valley systems are known to occur on the shelf off the larger fjord and are related to the melting of the Greenland Inland Ice. Using side-scanning sonar studies, selected parts of these valley systems will be surveyed and their origins investigated. The Ilulissat/Jakobshavn Glacier flows into the Disko Bay area, where the outflow of freshwater forms a freshwater plume, while the sea ice formation in winter results in the formation of salt water with high density. During the advances and retreats of the glacier front, the plume has changed position, and these changes will be surveyed. Furthermore, the Egedesminde Trench in the Disko Bay and the large submarine sediment fan flanking the shelf will be studied with a view to determining the mode of formation and the age of these geological structures.
The shelf off the west coast of Greenland displays features indicating that large numbers of icebergs have ground their way across the seabed during times of lowered sea level. The direction and extent of these plough marks will be surveyed using deep-tow sidescan sonar equipment. Studies will be carried out in the Disko Bay area in particular, where large icebergs from the Ilulissat Glacier are believed to have left deep tracks in the seabed; the direction and size of the tracks testify to changes in the direction and strength of the ice flows. Geophysical investigations will also provide information on features such as drowned coastlines, lateral moraines, turbidites and changes in the sea level.
In connection with sampling the seabed using a grab sampler off Ilulissat Icefjord, the sediments’ contents of Ice Rafted Detritus (IRD) will be examined. As this material can only originate from ice that has gathered its load from the bedrock, an analysis of the IRD will provide data on the nature of these rocks, which are presently covered by the ice stream.
A distinct Mid-Holocene reflector has previously been observed in the sediment succession off Christianshåb. This reflector can be reached using a piston corer, which will make it possible to date and examine the mode of formation of this distinctive surface.
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