A calibrated deglacial drainage chronology for the North American continent: evidence of an Arctic trigger for the Younger Dryas

We present a new deglacial meltwater drainage chronology for the North American ice-sheet complex using a 3D glacial systems model calibrated against a large set of palco-proxies. Results indicate that North America was responsible for a significant fraction of mwpl-a, with order 1.5dSv or larger (100 year mean) peak discharges into both the Gulf of Mexico and the Eastern Atlantic and less than I dSv into the Arctic Ocean. Our most significant result concerns discharge into the Arctic Ocean. The largest total discharge into the Arctic Ocean (ensemble mean values of 1.0-2.2dSv) occurs during the onset of the Younger Dryas. The large majority of this discharge is locally sourced with reduction of the Keewatin ice dome being the largest contributor. Given that the only outlet from the Arctic Basin at this time was via Fram Strait into the Greenland-Iceland-Norwegian Seas, we hypothesize that this pulse was the trigger for the re-organization of thermohaline circulation that is thought to have been responsible for the Younger Dryas cold interval. In contradistinction with past inferences and subject to the imperfectly constrained ice-margin chronology, we also find that the Northwest outlet likely dominated much of the post -13 ka drainage of Lake Agassiz. (C) 2006 Elsevier Ltd. All rights reserved.