Response of Norwegian Sea temperature to solar forcing since 1000 A.D.

Abstract

We report on a 1000 year long oxygen isotope record in sediments of the eastern Norwegian Sea which, we argue, represents the temperature and transport of warm Atlantic waters entering the Nordic Sea basin via the North Atlantic Drift and the large-scale Meridional Overturning Circulation. The single-sample resolution of the record is 2.5-10 years and age control is provided by 210Pb and 137Cs dating, identification of historic tephra, and a 14C "wiggle-match" dating method in which the surface reservoir 14C age in the past is constrained rather than assumed, thereby eliminating a large source of chronological uncertainty. The oxygen isotope results indicate decade- to century-scale temperature variations of 1-2°C in the shallow (∼50 m deep) subsurface which we find to be strongly correlated with various proxies of past solar activity. The correlations are synchronous to within the timescale uncertainties of the ocean and solar proxy records, which vary among the records and in time with a range of about 5-30 years. The observed ocean temperature response is larger than expected based on simple thermodynamic considerations, indicating that there is dynamical response of the high-latitude ocean to the Sun. Correlations of our results with a gridded temperature reconstruction for Europe are greater in central Europe than in coastal regions, suggesting that the temperature and transport of warm Atlantic waters entering the Nordic Basin and the pattern of temperature variability over Europe are both the proximate responses to a change in the atmospheric circulation, consistent with a forced shift in the primary modes of high-latitude atmospheric variability. © 2010 by the American Geophysical Union.