Thinning and retreat of the temperate Connemara ice centre, Ireland, during Heinrich Stadial 1 constrained with cosmogenic 10Be dating

Abstract

Within the North Atlantic region, climatic perturbations such as Heinrich Stadial 1 (HS1) and the Younger Dryas stadial (YD) have traditionally been viewed as anomalous periods of extreme cooling linked to abrupt changes in the poleward oceanic transport of heat. While there is considerable geologic data to support strong cooling during stadial winters, recent work in mid- and high-latitude regions fringing the North Atlantic suggests that this thermal signal did not extend to stadial summers, contrary to previously inferred palaeoecological and ice core proxies. Some directly dated glacial records from Britain, Ireland, and Scandinavia, for instance, document the large-scale retreat of terrestrial ice masses during both HS1 and the YD, coincident with meltwater pulses from the European continent and consequent weakening of Atlantic meridional overturning circulation. Similar patterns of stadial deglaciation have been reported from Greenland and north-east North America. Together, these datasets support the emerging model of stadials as periods of anomalous seasonality imposed on the strongly maritime North Atlantic climate. In this study, we present a geologic record of ice sheet behaviour from the Maumturk Mountains in western Ireland during the last glacial termination, constrained with cosmogenic ¹⁰Be surface-exposure dating. Coupled with glacio-geomorphologic and sedimentologic characterisation of moraine landforms, our record describes a temperate ice mass undergoing sustained active retreat during the first half of HS1, synchronous with increased European meltwater discharge into the North Atlantic.