Seager also takes issue with the usual interpretation of the Younger Dryas, a cold snap that struck the North Atlantic region 12,900 years ago. It is typically ascribed to a shutdown of the thermohaline circulation brought on by the collapse of a glacial dam, which released a pulse of fresh water, squelching the "haline" aspect of the circulation. Seager argues that the cooling predated the dam collapse.
Read more here