Increased precipitation in NW Europe triggered by the Hudson Bay Ice Saddle collapse

The collapse of the Hudson Bay Ice Saddle (HBIS), whose freshwater signal is dated between 8.6 and 8.5 ka b2k, is increasingly viewed as the primary driver of the abrupt '8.2 ka' cooling anomaly. Yet linking the two implies that the climatic repercussion of the HBIS collapse lagged by centuries – a delay at odds with some climate models projecting that meltwater forcing can influence climate change within just a few decades. Here, we present a stalagmite-based geochemical record spanning 11.1–7.5 ka from western Ireland – a region highly sensitive to the North Atlantic climate – that provides direct evidence that the HBIS collapse triggered a rapid hydroclimatic change in the region. Based on the stalagmite δ18O, mirroring North Atlantic seawater δ18O, and its Sr/Ca data, we document a pronounced increase in precipitation coinciding with the HBIS collapse and a slowdown of the AMOC at 8.6 ka. This precipitation trend persists throughout the '8.2 ka' event and does not return to the level pre-HBIS collapse until 7.9 ka, suggesting a slow recovery of the hydroclimate, independent of temperature direction. Our findings outline what may lie ahead for NW Europe in the coming decades if meltwater flux keeps accelerating and the AMOC weakens.