Climate Science

A Reason to Surge

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Science  12 Aug 2011:
Vol. 333, Issue 6044, pp. 803
DOI: 10.1126/science.333.6044.803-c

Heinrich events—massive, episodic iceberg discharges from the Laurentide Ice Sheet into the north Atlantic Ocean during the last glacial period—once were thought to be the consequence of internal ice sheet stability: the inability of the ice sheet to remain intact after having grown to a particularly large size. Support for this view has eroded over the past decade, however, and the suggestion that the events are instead the consequence of external causes, such as solar variability or the addition of glacial meltwater into the adjacent surface ocean, have gained favor. Marcott et al. add to that line of thought, with a combination of data from benthic foraminifera and results from a climate-model simulation, which suggest that basin-wide subsurface warming occurred at the same time as large reductions in Atlantic deep circulation, with subsurface temperature increasing by approximately 2° C during the 1000- to 2000-year interval before a Heinrich event. Such a temperature rise would erode the floating ice shelves that buttress terrestrial ice streams, and produce massive iceberg discharges. This finding could have important implications about how these ice sheets might behave in the future in our warming climate.

Proc. Natl. Acad. Sci. U.S.A. 108, 10.1073/pnas.1104772108 (2011).

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