A radiocarbon controlled stable isotope record from Seneca Lake, New York, has defined a relatively cold paleoclimate (10.1–8.2 ka) that was younger, and regionally of greater magnitude, than the well-known Younger Dryas cold interval. These new isotope results are supported by published pollen records, from throughout the Great Lakes region, that also define a relatively cold paleoclimate at this time. This cold paleoclimate occurred during global meltwater pulse IB when large volumes of cold, isotopically light (low δ18O) meltwater flowed into the Great Lakes from the rapidly retreating Laurentide ice sheet. The discharge of cold glacial meltwaters into the Great Lakes during pulse IB suppressed downwind summer temperatures in the Finger Lakes region and provided a source of isotopically light precipitation. Published proxy data from Greenland, Norway, and Alaska also record relatively cold paleoclimates following the Younger Dryas, suggesting widespread Northern Hemisphere cooling as a direct result of the rapid melting of the Laurentide ice sheet between 10 and 8 ka.

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