ALLEROD COLLAPSE OF THE NEWFOUNDLAND ICE CAP, NORTHWESTERN ATLANTIC OCEAN

The island of Newfoundland is situated at the junction of the Labrador Current and Gulf Stream, the two principal thermohaline currents of the northwestern Atlantic. Control on the timing of deglaciation of the island was mostly restricted to offshore records although a few lakes have yielded latest Pleistocene paleovegetation proxies of paleoclimate. Twenty-three cosmogenic ¹⁰Be ages on boulders throughout Newfoundland have a range of 11.6 to 14.1 ka and mean of 13.1±0.1 ka (standard error). The samples indicate synchronous deglaciation in all the regions sampled over a >100,000 km² area: St. John's Highlands (on the Great Northern Peninsula once believed to be a nunatak); head of White Bay (northcentral NF); Gaff Topsails Region central NF; Anniopsquotch Mountains and Burgeo region (southwestern NF); Granite Lake (southcentral NF); head of Baie d'Espoir (southern NF); and northern Burin Peninsula (southeastern NF). The large (>2 m) boulders with flat horizontal surfaces are unlikely to have been influenced by snow cover, exhumation through till, boulder erosion, or inheritance. The rate of deglaciation is similar to rates of late Holocene deglaciation on Baffin Island, also based on ¹⁰Be chronology. University of Maine Ice Sheet Model (UMISM) simulations of ice cover during deglaciation of the island provide estimates of ice volume during the last phase of deglaciation. A minimum ice volume of 40,000 km³ would have been released to the northwestern Atlantic Ocean over a short time (probably <2 ka) for a minimum meltwater flux of about 0.001 Sv just prior to and during the Younger Dryas cooling event. The particular location of this small discharge warrants further investigation into its affects on the wind-driven Gulf Stream and dynamics of the north Atlantic gyre, and the response of the Labrador Current.