Causes, consequences and chronology of large-magnitude palaeoflows in Middle and Late Pleistocene river systems of northwest Europe.

Abstract

This study examines the record of high-palaeoflow phases in river systems in northwest Europe, investigating their causes (whether due to ‘unique’ events, such as the formation of the Dover Strait, or as ‘characteristic’ consequences of climate change), examining their consequences with regard to landscape evolution and possible effects on climate, and determining the chronology of key events. Large-magnitude palaeoflows, more than an order-of-magnitude larger than present-day flood peaks, are shown to be characteristic of rivers in this region at particular times within the Pleistocene. These events, the most recent of which were during Heinrich events 2 and 1 at ∼25 and ∼17 ka, were evidently caused by the combined effects of glacial outwash, rainfall, snowmelt and melting of permafrost in some proportion. They released such large volumes of water that the thermohaline circulation of the Atlantic Ocean, and thus the climate, may well have been affected. These large-magnitude palaeoflows are thus a significant aspect of the Pleistocene Earth system that has hitherto gone unquantified.