Glacial Runoff From North America and its Possible Relationship to Changes in Ocean Circulation and Climate
Abstract
Drainage basins during advances and retreats of the Laurentide Ice Sheet (LIS) were much different than today. Preglacial northward- and eastward-draining rivers were dammed by the advancing LIS, and rivers were diverted to other oceans; these new glacial routes evolved through time in response to ice margin fluctuations, isostasy, ice and land topography, and incision of drainage routes. A complex history of North American drainage developed following the Last Glacial Maximum. The main glacial routes for continental runoff were south through the Mississippi River to the Gulf of Mexico, east through the Great Lakes and then to the North Atlantic via the Hudson or St. Lawrence valleys, and northwest via the Athabasca-Mackenzie Valley to the Arctic Ocean. Postglacial drainage routes were establshed about 7.7 14C ka [8.45 cal ka], when Lake Agassiz breached the LIS in Hudson Bay basin and sent its remaining 163,000 km3 into the North Atlantic Ocean. Recent research on the eastern and northwestern outlets from Lake Agassiz, which played a major role in routing runoff from the continent, is prompting new thinking about the chronology of use of these outlets and their downstream river and ocean connections, especially during the Younger Dryas. Meltwater and precipitation runoff to the oceans was episodically supplemented by the release of stored water from ice-marginal lakes; during its latter stages (11-7.7 14C ka [13-8.45 cal ka]), Lake Agassiz provided by far the largest catastrophic additions. Because the flux of glacial runoff from North America has been linked to changes in thermohaline circulation (THC) and, in turn, to climate cooling, it is important to understand the chronology, routing, and magnitude of diversions and catastrophic outbursts from glacial basins. Outbursts may have triggered changes in THC and diversions may have sustained them.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMGC11A..02T
- Keywords:
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- 1600 GLOBAL CHANGE;
- 1620 Climate dynamics (3309);
- 1635 Oceans (4203);
- 1655 Water cycles (1836);
- 4267 Paleoceanography