High-Resolution Models Tell a Different Story About the Impacts of Gigantic Meltwater Floods
The release of enormous volumes of glacial meltwater from large glacial lakes to the ocean in the Earth’s past have been correlated with periods of significant climatic cooling. It is believed that the meltwater would have spread across the northern North Atlantic inhibiting the sinking limb of the Atlantic Meridional Overturning Circulation (AMOC)—the large-scale circulation that brings relatively mild temperatures to North America and Europe. DOE scientists have tested this hypothesis by running a state-of-the-art, high-resolution climate model simulation of glacial flood outbursts and found, contrary to popular belief, that the meltwater would have been transported into the subtropical North Atlantic, a location 3000 km further south than previously thought. Unlike earlier studies, the meltwater remained on the continental shelf as a narrow, buoyant, coastal current with little offshore spreading, and did not interrupt the sinking limb of the AMOC. Indeed, when the investigators performed the experiment with a coarser resolution version of the same model, the freshwater spread across the sub-polar North Atlantic as in previous studies. To understand the climatic impact of freshwater released in the past or future (e.g., from Greenland and Antarctica) the ocean needs to be modeled at a resolution sufficient to resolve narrow, coastal buoyant flows.
Condron, A., and P. Winsor. 2011. “A Subtropical Fate Awaited Freshwater Discharged from Glacial Lake Agassiz,” Geophysical Research Letters 38, L03705, doi:10.1029/2010GL046011.