Abstract
AbstractCatastrophic meltwater drainage from glacial Lake Agassiz has been hypothesized as a trigger for large‐scale ocean circulation change initiating the Younger Dryas cold reversal. Here we quantify the flood discharge that formed the northwestern outlet of Lake Agassiz using a one‐dimensional step‐backwater model and a zero‐dimension gradual‐incision model. Applying these two independent models, we estimate a peak discharge range of 1.8–2.5 × 106 m3 s−1 and a flood volume of ∼21,000 km3. Such a discharge can only be derived from Lake Agassiz rather than one of the two smaller regional glacial lakes: Churchill or Meadow. When coupled with existing ice margin chronologies, these results demonstrate that the northwestern outlet of Lake Agassiz provides a viable link for catastrophic meltwater to drain to the Arctic Ocean over a 6–9 month period during the Younger Dryas, though it is unclear whether this was near its beginning.
Highlights
We estimate the discharge and demonstrate its connection to Lake Agassiz and the Arctic Ocean during the Retreat of the Laurentide Ice Sheet (LIS) during the last deglaciation resulted in large proglacial lakes forming on its receding southern and western margins
Catastrophic freshwater drainage of this lake at the start of the Moorhead Phase has been hypothesised as the trigger for large-scale ocean circulation and global climate change (Broecker et al, 1989; Licciardi et al, 1999; Clark et al, 2001; Teller et al, 2002; Teller & Leverington, 2004), resulting in the Younger Dryas (YD) cooling (12.9-11.7 ka BP)
We reconstruct the magnitude of catastrophic drainage from the northwestern outlet of Lake
Summary
Retreat of the Laurentide Ice Sheet (LIS) during the last deglaciation resulted in large proglacial lakes forming on its receding southern and western margins. Lake Agassiz, which occupied >1.5 million km during its existence (Teller & Leverington, 2004). Geomorphic evidence for the hypothesised northwestern drainage of Lake Agassiz is evident in western Canada, notably the Clearwater Lower Athabasca Spillway (CLAS: Figure 1). This >250 km long and 2-3 km wide incised channel and associated large-scale bedforms, record high magnitude discharge. The initial interpretation of the CLAS as the northwestern outlet of Lake
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