2 - The North Atlantic as a Quaternary magnetic archive  pp. 49-80

The North Atlantic as a Quaternary magnetic archive

By J. S. Stoner and J. T. Andrews

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Introduction

Sediments from the North Atlantic and its subarctic basins preserve exceptional archives of changing environmental conditions. High-resolution studies of North Atlantic sediments have shown that magnetic measurements are particularly sensitive to millennial-scale variations and can make significant contributions to our understanding of climatic and environmental variability. Until recently, measurements of magnetic susceptibility have been most widely used and reported in this environmental context. However, significantly more information can be obtained by using a variety of magnetic measurements. Magnetic methods provide a highly sensitive, high-resolution, rapid and non-destructive technique for quantifying lithologic variability which, in marine sediments, is often a direct response to changing environmental conditions. Within the dynamic context of the North Atlantic region, magnetic measurements can also provide information about sediment source and depositional mechanism. High-resolution magnetic studies are now becoming increasingly common, employing a range of magnetic parameters to provide a wealth of new information about the dynamics and inter-relationships of the Earth's environmental system. The growth and decay during the Quaternary of large, mid-latitude continental ice sheets have been linked to changes in the amount and seasonal distribution of incoming solar radiation. These insolation changes display periods of approximately 100, 41 and 23 kyr, due to changes in the Earth's eccentricity, tilt, and precession relative to the sun, respectively (Chapter 10 and e.g. Hays et al., 1976). However, the cryosphere/climate system is not completely linearly forced by these orbital variations, but varies as a complex response to many interactions between the ice sheets, oceans and atmosphere. Superimposed on these long period orbital variations are more rapid environmental changes that occur on much shorter time periods (102–103 years).