Intensified Meltwater Influx During Heinrich Stadial 1 Recorded in the Gulf of Maine, USA

Abstract Abrupt, millennial‐scale climate events characterize the most recent deglaciation. However, their nature remains poorly understood. Previous work has shown enhanced glacial melt signals from the European/Scandinavian Ice Sheet and a rapid recession of the Laurentide Ice Sheet (LIS) in Eastern Maine during Heinrich Stadial 1 (HS‐1). These observations challenge the idea that stadials were year‐round cold excursions in the Northern Hemisphere. We aim to determine if European HS‐1 melt signals are coeval with LIS meltwater in the Gulf of Maine (GOM) marine sediment record, which was ice‐proximal during much of the last deglaciation. Here we present geochemical records (δ 18 O, Mg/Ca, calculated δ 18 O seawater ) developed using benthic foraminifera from a new GOM sediment core, EN‐669‐GGC‐40, spanning ∼17.5–11.5 cal ky BP. We find that the documented portion of HS‐1 in the GOM can be divided into two phases: the earlier (HS‐1b, ∼17.5–15.9 cal ky BP) being characterized by large‐amplitude variations of δ 18 O sw , which we interpret as a series of intervals of enhanced meltwater runoff from the LIS. The later period (HS‐1a, ∼15.9–14.7 cal ky BP) is characterized by a rapid and sustained isotopic depletion of δ 18 O sw from 15.7 to 15.3 cal ky BP which we interpret as a persistent melting episode, consistent with rapid collapse of glacial ice in Eastern Maine. Our results support the hypothesis that HS‐1 was characterized by warm(ing) summers and hypercold winters in the North Atlantic region (Denton et al., 2005, https://doi.org/10.1016/j.quascirev.2004.12.002 , Denton et al., 2022, https://doi.org/10.1016/j.quascirev.2022.107750 ).