Climate Science

Freshwater Triggers

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Science  10 Jan 2003:
Vol. 299, Issue 5604, pp. 167
DOI: 10.1126/science.299.5604.167d

Climate records of the late Pleistocene from the North Atlantic region indicate a strong link between large-scale ocean circulation and iceberg discharges from ice sheets. Climate models and observational data point to the impact of meltwater on thermohaline forcing, but the mechanism responsible for the submillennial scale instability of marine ice margins remains unclear.

Knutz et al. present a paleoclimatic record of the last deglaciation, from the northeast Atlantic margin, which captures a detailed picture of the interaction between ocean circulation and ice sheets in northwest Europe. A moderate elevation of sea surface temperatures triggered a series of multidecadal ice-rafting events, culminating in a major meltwater discharge 17,500 years ago. A similar sequence is also apparent during the B∅lling-Aller∅d to Younger Dryas transition 12,700 years ago. The authors suggest that the initial cooling observed in many North Atlantic records before the massive iceberg discharge event (Heinrich-1) that occurred near the beginning of the Younger Dryas is likely to be the effect of meltwater discharge from European ice sheets. These results provide important details in support of the idea that a sensitive and rapid response of ice sheets in northwest Europe occurred because of transient increases in thermohaline heat transport. — HJS

Geochem. Geophys. Geosys. 3, 10.1029/2002GC000351 (2002).

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