Lake Agassiz during the Younger Dryas

Abstract

Lake Agassiz was ponded on the northward-sloping surface of the Hudson Bay and Arctic Ocean basins, as the Laurentide Ice Sheet retreated. The level of Lake Agassiz abruptly fell ~ 12.9 cal (11 14C) ka BP, exposing the lake floor over a large region for > 1000 yr. The routing of overflow during this (Moorhead low-water) period is uncertain, and there is evidence on the continent and in ocean basins for both an easterly route through the Great Lakes–St. Lawrence to the North Atlantic and for a northwesterly route through the Clearwater–Athabasca–Mackenzie system to the Arctic Ocean. The Moorhead low water phase coincides with the Younger Dryas cooling, and a cause–effect relationship has been proposed by attributing a change in ocean thermohaline circulation to the re-routing of Lake Agassiz freshwaters from the Gulf of Mexico to more northern oceans. Paleoclimatic interpretations from ecosystems in lake sediments in the region, and a simple calculation of the paleohydrological budget of Lake Agassiz, indicate that the climate remained wet and cool throughout the YD in this region, and was not warm nor dry enough to allow evaporative loss to offset the influx of meltwater and precipitation; thus, the Moorhead phase resulted from changes in the outlet that carried overflow.

Deglaciation of the Laurentide Ice Sheet from the Last Glacial Maximum

“…Dixon, 1999;Goebel et al, 2008;Eriksson et al, 2012;Pedersen et al, 2016), but also in relation to the routing of meltwater from Glacial Lake Agassiz (Smith and Fisher, 1993;Fisher and Smith, 1994;Fisher et al, 2002;Tarasov and Peltier, 2005;Murton et al, 2010;Fisher and Lowell, 2012;Teller, 2013; see Section 3.3). The rapid collapse of the saddle between the LIS and CIS has also been hypothesised as a potential source of meltwater pulse 1A (Gregoire et al, 2012(Gregoire et al, , 2015a, although the precise contributions from North America are subject to ongoing debate Carlson and Clark, 2012;Deschamps et al, 2012).…”

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…Teller et al, 2000;Lepper et al, 2013); (3) data-calibrated numerical ice sheet modelling (Tarasov and Peltier, 2006); (4) the palaeo-topography of the basin inferred from isostatic rebound (e.g. Leverington et al, 2000;2002;Rayburn and Teller, 2007); and (5) the dating of meltwater events in the different outlet channels, and in lakes and oceans beyond the channel mouths (Section 2.6), including the use of deep sea oxygen isotope records and distinctive sediment discharge to identify meltwater pulses (Fisher, 2007;Hillaire-Marcel et al, 2008;Lowell et al, 2009;Lewis et al, 2012;Fisher and Lowell, 2012;Teller, 2013).…”

“…It has been argued that overflow from GLA may have triggered the YD stadial, but there is uncertainty as to whether it overflowed to the east, to the northwest, or did not overflow at all (Lowell et al, 2009;Fisher and Lowell, 2012;Lowell et al, 2013;Teller, 2013). Opinions differ about precise timing and routing of GLA overflow during the YD, because different approaches often yield different interpretations (e.g.…”

“…Ocean response is also highly sensitive to the location of meltwater injection (Condron and Winsor, 2012) and the spatial pattern of freshwater injection needs to be taken into account (Jongma et al, 2013). A related complication is the apparent sensitivity of the modelled climate system response to meltwater injection to the background state of the ocean-climate system (Kageyama et al, 2010;2013).…”

Evidence for meltwater drainage via the St. Lawrence River Valley in marine cores from the Laurentian Channel at the time of the Younger Dryas

“…In his review of the literature about Lake Agassiz, Teller (2013) concluded that the question as to which path the Lake Agassiz floodwaters took has not been resolved yet. It might simply be that evidence for a large catastrophic drainage event is lacking, unless the meltwater drainage did occur subglacially as proposed by Livingstone et al (2013), in which case, no such sedimentary evidence will be found.…”