Application of Tephrochronology to the Dating of a Multi-proxy Study of High Resolution Marine Shelf Records at the North Atlantic Oceanographic Polar Front
Résumé
The chronology of marine sediment cores from high resolution basins on the North Icelandic shelf is based on combined tephrochronology and AMS 14C datings. Reliably dated tephra markers provide age control for archives of Holocene palaeoceanographic changes in the vicinity of the oceanographic Polar Front. The present position of the Polar Front separates Arctic surface water of the East Greenland and the East Icelandic currents (Polar Water) from branches of the North Atlantic Current, the Irminger Current (Atlantic Water) to the west and north of Iceland. The area is also within the realm of the Arctic Front that delineates the maximum extent of the winter sea ice, which periodically extends from Greenland to Iceland. The Norwegian Sea Deep Water replaces the surface and intermediate water masses at a depth of 300-400 m off North Iceland. The modern salinity and temperature data from the area show that the deep water masses may be expected to encroach into topographic lows and basins on the shelf during periods of active deep water formation in the Nordic Seas. Another climatic boundary is represented by the North Atlantic Atmospheric low-depression track and the accompanying westerlies across Iceland. The strong gradients both in the ocean and in the atmosphere make this region extremely sensitive to climatic changes.