Geological cores - sediment records

Katrine Husum
Task leader
Norwegian Polar Institute

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Knowledge about past environmental conditions, for example water temperatures and sea ice conditions, is important for establishing natural reference values that increase our understanding of the causes and consequences of current and future climatic and environmental changes.

In order to decipher water temperatures and sea ice conditions beyond the time of instrumental measurements, the Nansen Legacy studies sediment cores, which are obtained by pushing a pipe into the seafloor. The cores contain deposits that have accumulated at the bottom of the sea over time The deposits contain grains of various size and colour, as well as fossil plankton and animals, and other geochemical and biological “fingerprints”. All these parameters reflect the environmental conditions at the time when the organisms were alive and when the sediments were deposited. This includes the temperature of the seawater and amount of sea ice back in time. Looking at the sediment records allows, for example, to identify the Atlantic signal and fluctuations of sea ice in the northern Barents Sea in the past. This knowledge provides a natural baseline that is necessary to put the current environmental and climatic changes into a long-term perspective.

The Nansen Legacy has retrieved sediment cores at twelve locations along the Nansen Legacy main transect during the Nansen Legacy Paleo cruise by using a multi corer (up to 60 cm long) and a gravity corer (up to 6 m long). In addition, a piston corer was used at some sites, allowing the retrieval of longer cores. The longest core was 21.6 m long. In total, 96 multicores, 23 gravity cores and 6 piston cores were retrieved during the Nansen Legacy Paleo cruise.