On the reconstruction of ocean circulation and climate based on the "gardar Drift"

Abstract

Sediment-based reconstructions of bottom water velocity at the Gardar Drift are commonly interpreted to reflect changes in the eastern Nordic Seas overflows. Here we investigate the relationship between changes in the water that overflows through the Faroe Shetland Channel and downstream bottom velocity at the location of the Gardar Drift as represented in a 500 year long simulation with the Bergen Climate Model. We identify a region in our simulation proximal to the geographical location of the northern Gardar Drift where 76% of the variance in bottom velocity can be explained by changes in the volume transport and density of the Faroe Shetland Channel overflow. By contrast, Labrador Sea Water changes do not appear to play a significant role in the bottom flow over the Gardar Drift. Our findings support the assumption in the paleo literature that reconstructions of bottom water velocity at the Gardar Drift reflect past changes in the eastern Nordic Seas overflows. However, our results suggest that velocity changes downstream are not a simple metric for the strength of the overflow, rather overflow density plays the largest role.