Passage:
In paleoclimatology, the abrupt 'Younger Dryas' cooling event—a sudden return to glacial conditions roughly 12,900 years ago—has long been attributed to the catastrophic outburst of Lake Agassiz, which routed massive volumes of freshwater into the North Atlantic and disrupted the Atlantic Meridional Overturning Circulation (AMOC). However, recent high-resolution ocean sediment cores from the Arctic Ocean reveal that freshwater discharge into the Arctic Basin via the Mackenzie River system peaked simultaneously with the onset of cooling, whereas North Atlantic meltwater markers lag the cooling event by nearly two centuries. Based on these findings, paleoclimatologist Dr. Vance asserts that Arctic freshwater influx, rather than North Atlantic discharge, was the primary trigger for the AMOC shutdown. Vance argues that Arctic sea-ice expansion, driven by Mackenzie River runoff, significantly increased surface albedo and restricted ocean-atmosphere heat exchange, thereby destabilizing the global thermohaline conveyor prior to any major Atlantic influx.
Statement:
Oceanographic modeling reveals that freshwater entering the Arctic Basin via the Mackenzie River system is rapidly diverted into the North Pacific Ocean through the Bering Strait, preventing it from reaching the North Atlantic upper ocean layers that drive the AMOC.
Evaluating the statement above: If true, this finding weakens Dr. Vance’s assertion regarding the primary trigger of the AMOC shutdown.
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