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North Atlantic climate variability in early Palaeogene time: a climate modelling sensitivity study

By
Lisa Cirbus Sloan
Lisa Cirbus Sloan
Department of Earth Sciences, University of CaliforniaSanta Cruz, Santa Cruz, CA 95064, USA (e-mail: lcsloan@earthsci.ucsc.edu)
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Matthew Huber
Matthew Huber
Department of Earth Sciences, University of CaliforniaSanta Cruz, Santa Cruz, CA 95064, USA (e-mail: lcsloan@earthsci.ucsc.edu)
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Published:
January 01, 2001

Abstract

Understanding the nature and causes of the variability associated with past warm, high pCO2 climates presents a significant challenge to palaeoclimate research. In this paper we investigate the early Eocene climatic response in the North Atlantic region to forcing from an indirect effect of atmospheric methane (via polar stratospheric clouds (PSCs)), and we investigate the response of the climate system to forcing from a combination of orbital insolation changes and high atmospheric pCO2 concentration. We find that sea surface temperatures (SSTs), sea ice extent, net surface moisture, continental runoff and upwelling in the North Atlantic Ocean are all sensitive to those forcing factors, and that the degree of sensitivity is a function of location and season. Our results suggest that high-latitude SST values can vary by as much as 20 °C during the winter season in response to precessional and polar cloud forcing, whereas in contrast summer temperature varies by 4 °C or less. Model predictions of net surface moisture balance also vary substantially with our prescribed forcing. There is a large difference in variability between the localized net surface moisture results and the mean North Atlantic Ocean results, which suggests that large-scale assumptions about past surface ocean salinities and seawater δ18O may need to be reassessed. According to model results, the influx of terrigenous material via continental runoff to the North Atlantic Ocean should be highly seasonal, with greatest runoff occurring in spring. Our model results also indicate that changes in wind-driven upwelling and in continental runoff on a precessional time scale should be seen in regions of the central North Atlantic.

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Contents

Geological Society, London, Special Publications

Western North Atlantic Palaeogene and Cretaceous Palaeoceanography

Dick Kroon
Dick Kroon
University of Edinburgh, UK
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R. D. Norris
R. D. Norris
Woods Hole OI, USA
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A. Klaus
A. Klaus
Ocean Drilling Program, USA
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Geological Society of London
Volume
183
ISBN electronic:
9781862394315
Publication date:
January 01, 2001

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