HR: 1330h
AN: PP12A-0222    [PDF]
TI: Climate Variability During the Last 1200 Years: Evidence From the North Icelandic Shelf
AU: * Eiriksson, J
EM: jeir@rhi.hi.is
AF: Science Institute, University of Iceland, Dunhaga 3, Reykjavik, IS-101 Iceland
AU: Knudsen, K L
AF: Department of Earth Sciences, University of Aarhus, Aarhus C, DK-8000 Denmark
AU: Jiang, H
AF: Laboratory of Geographic Information Science, East China Normal University Shanghai, Shanghai, 200062 China
AB: Marine sediment cores from high resolution basins on the North Icelandic shelf provide reliably dated archives of Holocene palaeoceanographic changes in the vicinity of the 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. The chronology for the North Icelandic shelf work is based on combined tephrochronology and AMS 14C datings. A marine reservoir correction of 400 years is generally applied for Holocene datings in the region. However, recent results from the North Icelandic shelf show that the reservoir age has not been constant in the area through Holocene time. Tephrochronology enables us to obtain independent control on radiocarbon datings from sedimentary records in an oceanographic boundary region between Atlantic and Arctic water masses. Icelandic tephra markers can be traced by the help of chemical analyses from volcanic source regions into the marine environment. The tephras are historically dated or dated on terrestrial material. A high-resolution record (200 cm/kyr), covering the last 1200 years, is dated by the help of nine well-known tephra marker horisons from volcanic eruptions in Iceland. A reconstruction of environmental changes, including the Medieval Warm Period (MWP) and the Little Ice Age (LIA), is based on sedimentological parameters, benthic and planktonic foraminiferal data, stable isotopes and diatom-based reconstructions of sea-surface temperatures. Both the summer (SSTs) and the winter (SSTw) sea-surface temperatures show multidecadal-to-centennial timescale fluctuations and the magnitude of fluctuations, from relatively warm to cold periods is about 1.0-1.5 degrees Celcius. There is a prominent drop in SSTs at AD 1300 and in both SSTs and SSTw at AD 1600. Changes in the sea-surface and bottom water environments, including temperature fluctuations, on the North Icelandic shelf are correlated with the MWP and the LIA. The timing of the relatively warm MWP (AD 850-1300) and the cold LIA (AD 1300-1900) north of Iceland corresponds to that reported in historical sources from Iceland. It is also in accordance with climatic changes recorded in Greenland ice cores and in Europe, as well as the Northern Hemisphere temperature anomaly fluctuations. Palaeoceanographic variations within the LIA on the North Icelandic shelf is also similar to the indication of the Iceland Sea Ice Index and other historical sources in Iceland.
DE: 3030 Micropaleontology
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 9325 Atlantic Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting