HR: 10:40h
AN: OS11B-02    [PDF]
TI: A Holocene Record of Changing Arctic Surface Ice Drift, Analogous to the Effects of the Arctic Oscillation
AU: * Darby, D A
EM: ddarby@odu.edu
AF: Old Dominion University, Dept. of Ocean, Earth, & Atmospheric Sciences, Norfolk, VA 23529 United States
AU: Bischof, J F
EM: jbischof@odu.edu
AF: Old Dominion University, Dept. of Ocean, Earth, & Atmospheric Sciences, Norfolk, VA 23529 United States
AB: The Arctic Oscillation (AO) controls the strength and location of the Trans Polar Drift (TPD), a system that exports ice through Fram Strait into the Nordic Seas. There, changing amounts of sea ice influence surface water salinity and the formation of North Atlantic deep water (NADW), and this, in turn has an impact on the global climate. Therefore, in order to understand how the global climate system functions it is imperative to know how the TPD changed over the last millennium or more. To that end we performed a provenance study on ice rafted sand grains in a sediment core located near the confluence of the counterclockwise TPD and the clockwise Beaufort Gyre. The core has more than 200 cm of Holocene sediment with intervals dominated by grains from the Siberian shelves alternating with intervals of abundant grains from North American sources. Grains matched to Siberian shelves indicate that the TPD was shifted toward North America similar to what occurs during a more positive phase of the AO. This scenario alternated with intervals where few grains matched to Russian sources. During the last 1300 years increased influx of Russian grains occurred approximately every 50-150 years. We suggest that this periodicity represents the long-term fluctuation of the AO, which produces the same TPD shift today. In addition, we found evidence for ice drift changes corresponding to the Medieval Warm interval from 900-1200 AD and at the end of the last deglaciation when glacial iceberg rafting rapidly declined. These more recent changes prior to the Little Ice Age were opposite in sense to the mineralogic changes at the last termination, and might indicate changes leading to the onset of the Little Ice Age.
DE: 1620 Climate dynamics (3309)
DE: 3022 Marine sediments--processes and transport
DE: 4267 Paleoceanography
DE: 4558 Sediment transport
DE: 9315 Arctic region
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting