Abstract

Few expeditions have gathered long sediment cores in the Amerasian Arctic Ocean and published results indicate extremely low sedimentation rates and sedimentary archives of little use for paleoclimatic and paleoceanographic studies. On the contrary, recent studies from the Eurasian Arctic Ocean (e.g. ACEX Drilling 2004) have shown high sedimentation rates indicating a great potential for paleoclimatic and paleoceanographic studies. However, the recently completed Healy-Oden Trans-Arctic Expedition (HOTRAX '05) obtained nearly 500 meters of sediment cores from the Northwind, Mendeleev-Alpha, Lomonosov, and Gakkel Ridges, Yermak Plateau, and Alaskan continental shelf and slope. This large cache of core material provides new material for the establishment of a pan-Arctic stratigraphy that will hopefully resolve the controversy over sedimentation rates in the Arctic and link the Eurasian and Amerasian sedimentary records. Preliminary estimates on some of the cores indicate very high sedimentation rates for at least the Holocene and possibly the last couple of glacial stages. The cores were the first to be collected in a transect across the central Arctic Ocean with detailed multibeam swath seafloor mapping and chirp seismic records to aid in the site selection and interpretation of the geologic context of each core. The preliminary results suggest that at least sub-century scale resolution should be obtainable for the cores collected on the canyon slopes north of Alaska. Fluctuations in sources of sea ice-rafted sediment in nearby cores suggest a link to the Arctic Oscillation, but on much longer than decadal scale fluctuations throughout the Holocene. Up to 80 color and textural cycles in the Quaternary are recognized in the long cores from the central Arctic ridges and these are probably linked to climatic cycles. A nearly two-fold increase in sedimentation is recognized from north to south along the Alpha-Mendeleev Ridge complex with the thickest units near the summer ice margin melt zone. Major discoveries during HOTRAX include the first ever mapping of mud waves on the seafloor in the Arctic and dramatic differences in the sill depth along the Lomonosov Ridge. This latter discovery has important implications for deep water exchange between the Amundsen and Markarov Basins.

Light refreshments are served in the Interaction Area (4th floor of the Oceanography/Physics Building) at 4:00 p.m.

All seminars begin at 3:00 p.m. and are held in room 200 of the Oceanography/Physics building.