Question

Passage:
For decades, paleoceanographers attributed the sudden onset of the Younger Dryas cold event—an abrupt reversal of post-glacial warming around 12,900 years ago—primarily to the catastrophic drainage of Lake Agassiz into the North Atlantic. According to this catastrophic discharge model, the massive influx of freshwater diluted surface salinity, thereby suppressing the Atlantic Meridional Overturning Circulation (AMOC) and halting North Atlantic heat transport. However, recent high-resolution isotopic analyses of marine sediments from the Nordic Seas have challenged the singular primacy of this mechanism.

While geochemical markers confirm that freshwater pulses occurred synchronously with thermohaline slowdowns, microfossil assemblages suggest that deep-water formation in the Norwegian Sea did not cease entirely, as early models posited. Instead, sea-ice expansion acted as an insulating barrier, altering local atmospheric pressure gradients and diverting mid-latitude westerlies southward. This atmospheric shift displaced precipitation patterns, which secondarily reinforced AMOC weakening by reducing oceanic salinity through increased localized rainfall rather than sole reliance on meltwater discharge.

Furthermore, comparative ice-core data from Greenland reveal that temperature drops preceded major freshwater runoff events in several sub-basins by up to two centuries. Consequently, contemporary researchers view the Younger Dryas not as an isolated hydrological accident triggered by a single meltwater outburst, but as a complex feedback loop where atmospheric realignment, sea-ice dynamics, and meltwater discharges mutually amplified one another. Although meltwater input remained a critical component, its role was likely that of a secondary amplifier rather than the sole initiating catalyst.

According to the passage, all of the following factors contributed to or characterized the Younger Dryas cold event EXCEPT: