7000 years of paleostorm activity in the NW Mediterranean Sea in response to Holocene climate events

A high-resolution record of paleostorm events along the French Mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the Gulf of Lions. Integrating grain size, faunal analysis, clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating, we recorded seven periods of increased storm activity at 6300-6100, 5650-5400, 4400-4050, 3650-3200, 2800-2600, 1950-1400 and 400-50 cal yr BP (in the Little Ice Age). In contrast, our results show that the Medieval Climate Anomaly (1150-650 cal yr BP) was characterised by low storm activity. The evidence for high storm activity in the NW Mediterranean Sea is in agreement with the changes in coastal hydrodynamics observed over the Eastern North Atlantic and seems to correspond to Holocene cooling-in the North Atlantic. Periods of low SSTs there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies. We hypothesise that the increase in storm activity during Holocene cold events over the North Atlantic and Mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large Central Atlantic-European domain. (C) 2011 University of Washington. Published by Elsevier Inc. All rights reserved.