Catastrophic Drainage From the Northwestern Outlet of Glacial Lake Agassiz During the Younger Dryas.

Catastrophic 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. Plain Language Summary: The Younger Dryas was a short‐lived interval of cooling that interrupted warming during the last deglaciation. The cause of this rapid change in climate is debated. One suggestion is the drainage of meltwater from glacial Lake Agassiz, a large ice‐dammed lake in central North America, into the surrounding oceans may have affected ocean circulation, contributing to this climatic event. Here we model the discharge of water from the northwestern outlet of this lake. We estimate the discharge and demonstrate the connection between Lake Agassiz and the Arctic Ocean during the Younger Dryas. Key Points: Peak discharge modeled for the northwestern outlet of glacial Lake AgassizMagnitude of drainage estimated at 1.8–2.5 × 106 m3 s−1 (1.8–2.5 Sv)Northwestern outlet of glacial Lake Agassiz provides a viable link for catastrophic meltwater to the Arctic Ocean during the Younger Dryas [ABSTRACT FROM AUTHOR]