Lateglacial climate change in the White Mountains of New Hampshire

Previous paleoecological studies of vegetation change based on pollen and plant macrofossil analyses have shown no evidence of Lateglacial climate reversals in the White Mountains of New Hampshire. We analyzed the carbon content and fossil midge fly assemblages of sediments from one high-elevation and two mid-elevation ponds in order to determine if Lateglacial climate reversals did occur. All three sites provide evidence for a major Lateglacial climate reversal that correlates with the Younger Dryas event (GS-1). A paleotemperature inference model based on fossil midges indicates a decline in maximum summer surface lakewater temperatures of about 5 degreesC. Because this decline is less than that experienced at similar sites in Maritime Canada and Maine, the impact of GS-1 appears to have been attenuated westward from the coast. Changes in organic content also provide evidence for the occurrence of a minor reversal immediately prior to the major one, but the chironomid data are inconclusive. This minor event likely correlates with GI-1b, the Killarney Oscillation. (C) 2001 Elsevier Science Ltd. All rights reserved.