Changes in the Bathymetry and Volume of Glacial Lake Agassiz between 9200 and 7700 ¹⁴C yr B.P.

Impact of floods versus routing events on the thermohaline circulation

“…[7] Three different meltwater events are simulated using reconstructed estimates of freshwater fluxes (floods and routing events) for the Younger Dryas (YD), the Preboreal Oscillation (PBO) and the 8.2-ka event [Licciardi et al, 1999;Leverington et al, 2000Leverington et al, , 2002Fisher et al, 2002;Clarke et al, 2004]. In each case, we integrate the model for over 5000 years into equilibrium under corresponding boundary conditions (orbital parameters [Berger, 1978] and atmospheric CO 2 of 240 ppm, 260 ppm and 260 ppm for the YD, PBO and 8.2-ka event, respectively).…”

Fresh arguments against the Shaw megaflood hypothesis. A reply to comments by David Sharpe on “Paleohydraulics of the last outburst flood from glacial Lake Agassiz and the 8200 BP cold event”

“…Specifically, these are the presence of an actively erupting volcano within the reservoir and the fact that the reservoir could be rapidly overfilled because the lake level was not subject to a topographic control. At the time of the final flood from Lake Agassiz, the lake level is thought to have been controlled by a spillway that routed water through the valley of the Kinoje´vis River to the valley of the Ottawa River (Vincent and Hardy, 1979;Veillette, 1994;Leverington et al, 2002). We estimated the height of this spillway as 230 m above sea level at that time.…”

Constraining ocean diffusivity from the 8.2 ka event

“…For a detailed comparison of the 9 kyr state to the preindustrial state in CLIMBER-2.3 see (Bauer et al 2004). In the simulation runs, the cold event is then forced at 8,200 years BP by a freshwater pulse released to the northern Atlantic Ocean, 5 representing a pulse-like drainage of melt water from the Lake Agassiz through Hudson Bay as suggested by Teller et al (2002) and Leverington et al (2002). This pulse has a volume of 1.6 9 10 14 m 3 and was released very quickly (\1 year; Teller, 2007 personal communication).…”

“…Renssen et al 2001;Renssen et al 2002;Bauer et al 2004;LeGrande et al 2006) that have been able to reproduce an asymmetric cold event induced by freshwater pulses of different strength and duration. Evidence of the drainage of glacial lakes Agassiz and Ojibway in an outburst at about 8470 BP ( 14 C time) (Liccardi et al 1999;Leverington et al 2002;Teller et al 2002) deliver a plausible scenario of a strong pulse-like freshwater forcing to the North Atlantic region for the time of interest. The causal link between the drainage of lake Agassiz and the weakening of North Atlantic ocean circulation has recently been supported by proxy records taken in the Labrador bassin (Kleiven et al 2008).…”