Lateglacial Shifts in Seasonality Reconcile Conflicting North Atlantic Temperature Signals
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AbstractThe accelerating flux of glacial meltwater to the oceans due to global warming is a potential trigger for future climate disturbance. Past disruption of Atlantic Ocean circulation, driven by melting of landbased ice, is linked in models to reduced oceanatmosphere heat transfer and abrupt cooling during stadial events. The most recent stadial, the Younger Dryas (YD), is traditionally viewed as a severe cooling centered on the North Atlantic but with hemispheric influence. However, indications of summer warmth question whether YD cooling was truly yearround or restricted to winter. Here, we present a beryllium10dated glacier record from the northeast North Atlantic, coupled with 2D glacierclimate modeling, to reconstruct Lateglacial summer air temperature patterns. Our record reveals that, contrary to the prevailing model, the last glacial advance in Scotland did not occur during the YD but predated the stadial, while the YD itself was characterized by warmingdriven deglaciation. We argue that these apparently paradoxical findings can be reconciled with regional and global climate events by invoking enhanced North Atlantic seasonalitywith anomalously cold winters but warming summersas an intrinsic response to globally increased poleward heat fluxes.
