HR: 09:45h
AN: GP51A-08 INVITED    [Abstracts]
TI: Magnetic and Modelling Approaches to Ocean Circulation at the Last Glacial Maximum
AU: * Maher, B A
EM: b.maher@lancs.ac.uk
AF: Lancaster Environment Centre, Lancaster University, Lancaster, Lan LA1 4YQ, United Kingdom
AU: Watkins, S J
EM: sarah.watkins@lancs.ac.uk
AF: Lancaster Environment Centre, Lancaster University, Lancaster, Lan LA1 4YQ, United Kingdom
AU: Bigg, G R
EM: grant.bigg@sheffield@lancs.ac.uk
AF: Geography Department, Sheffield University, Sheffield, Yor S10 2TN, United Kingdom
AB: The N. Atlantic plays a key role in global climate through formation of N. Atlantic Deep Water, which is a major driver of the thermohaline circulation. To understand past and future climate change, it is essential to understand the processes occurring within the N. Atlantic both at the present day and in past glacial stages. Debate exists over the ocean circulation state during glacial stages, some geological and modelling studies suggesting similar, or higher, rates of NADW advection during the Last Glacial Maximum (LGM), others indicating decreased NADW and increased formation of Southern Ocean deep water. Here, we use a suite of susceptibility and remanence measurements of ocean-wide N Atlantic sediments to test two different potential LGM ocean general circulation model results, by comparing the modelled iceberg trajectories each produces with magnetically- mapped patterns and sources of LGM ice-rafted debris (IRD). The two LGM states are characterised by: vigorous NADW formation; and deep water production in the Southern Ocean. We use cluster analysis of sediment magnetic properties to characterise N. Atlantic IRD patterns and sources at the present day and at the LGM. The LGM IRD patterns match most closely iceberg trajectories arising from the 'southern-sinking' ocean circulation state. Two major IRD sources at the LGM are indicated by the magnetic data, Fennoscandia and Greenland/Iceland, and one minor source, the St Lawrence region. The model and magnetic data suggest that the LGM N. Atlantic circulation was dominated by a cyclonic central N. Atlantic gyre, separated from the N. Atlantic Current which was displaced south of ~ 42°N.
UR: http://geography.lancs.ac.uk/cemp/publications/07_Watkins%20etal.pdf
DE: 1512 Environmental magnetism
DE: 4532 General circulation (1218, 1222)
DE: 4926 Glacial
DE: 4962 Thermohaline
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting