Magnetic characterisation of present-day deep-sea sediments and sources in the North Atlantic

Abstract

The North Atlantic plays a key role in global climate through formation of North Atlantic Deep Water, which drives the thermohaline circulation. To understand past and future climate change, it is essential to understand the processes occurring within the present-day North Atlantic but ocean-wide studies of present-day sediment distribution and sources are relatively sparse. Here, we use magnetic measurements to characterise the surface sediments of the North Atlantic and identify the major climatic and oceanographic controls on their magnetic signatures. The magnetic data, and subsequent cluster analysis, identify distinct spatial patterns of sediment sources and transport pathways. Much of the sedimentary magnetic signal appears to be controlled by detrital inputs, especially of windblown dust, and ice-rafted debris (IRD), with a range of different sources. These sediment transport pathways can be validated by making direct comparison of the sediment magnetic properties with source rocks and soils, and with iceberg trajectory and observation data. The spatial distributions of the IRD-dominated sediments substantiate those mapped previously using lithological tracers, provide additional spatial information on sediment sources and pathways, and suggest that deep water currents are less significant than proposed in controlling present-day sediment mineralogy and distribution. The data form a present-day basis for comparison with glacial-stage IRD and dust distributions, and modes of ocean circulation.