HR: 0830h
AN: PP51C-0936    [PDF]
TI: Bedform Evolution on Eirik Drift: HiRes MCS Evidence of North Atlantic Deep Water Variability Along the SW Greenland Margin
AU: * Earley, R J
EM: rearley@eden.rutgers.edu
AF: Rutgers University, Department of Geological Sciences Wright Geological Laboratory 610 Taylor Rd, Piscataway, NJ 08854 United States
AU: Mountain, G S
EM: gmtn@rci.rutgers.edu
AF: Rutgers University, Department of Geological Sciences Wright Geological Laboratory 610 Taylor Rd, Piscataway, NJ 08854 United States
AU: Wright, J D
EM: jdwright@rci.rutgers.edu
AF: Rutgers University, Department of Geological Sciences Wright Geological Laboratory 610 Taylor Rd, Piscataway, NJ 08854 United States
AU: Manley, P
EM: manley@middlebury.edu
AF: Middlebury College, Department of Geology Bicentennial Hall, Middlebury, VT 05753 United States
AB: The poleward flow of surface water in the North Atlantic transports heat to the northern North Atlantic, and leads to the export of deep, cold water towards the equator. While basinwide thermohaline circulation is ultimately controlled by global climate, bottom topography and Coriolis forces intensify or dissipate these currents on a regional scale. This gives rise to spatial and temporal variations in the distribution and intensity of ocean currents and significant variations in the rate and character of deep sea sedimentation which, if understood, can provide valuable insight into the history of this ocean circulation spanning millions of years. We report on results of a seismic survey of buried bedforms within a larger study of current-controlled sedimentation in the North Atlantic conducted aboard cruise 166-14 of the {\it R/V Knorr}. A series of at least six quasi-sinusoidal subbottom sediment buildups (averaging 1750 m long and 150 m high) are identified in a 15 x 35 km grid of high-resolution multichannel seismic reflection profiles in roughly 2500 m of water on the northwestern flank of Eirik Drift (150 km south of the southern tip of Greenland). Thickness changes within each buildup suggest that sedimentation rates varied by a factor of 3 over a distance of 3 km. In contrast to fields of sediment waves growing in unison across a large tract of seafloor, these features accumulated one at a time, each moving 1 to 3 km upslope of the one it replaced. We suggest these were the result of sediment fallout from the upslope edge of North Atlantic Deep Water (NADW) sweeping northwest along the Labrador Sea margin of Greenland. Long-standing intervals of sustained current-bedform interaction developed single sediment buildups, but periods of greater volume of NADW would overstep the existing bedform, and the depocenter would rapidly move upslope. The presence of a 40 to 60 m drape of sediment over the survey area chronicles a substantially different flow regime compared to that which formed the bedforms. Documenting the onset and termination of this flow pattern by drilling will provide a means to interpret fundamental modes and variations of the circulation of deep currents in the North Atlantic over the past several million years. These sequentially-formed, thick lenses of high-deposition-rate sediments provide an ideal location for collecting high resolution proxy data of climate change and its impact on ocean circulation.
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 4267 Paleoceanography
DE: 4558 Sediment transport
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting