IS THERE A LITTLE ICE AGE SIGNAL IN NEW ENGLAND LAKE SEDIMENTS?

The cold climatic period known as the Little Ice Age has been suggested in New England by historical documents and anecdotes, as well as some paleoecological evidence. In a palynological study of late Holocene vegetation change in central Massachusetts we noted declines in hemlock and beech that predate European settlement in the area, and coincide with the approximate dates of the Little Ice Age (about 1300? to 1850 AD). This same phenomenon is evident in pollen sites throughout the northeast. In an effort to investigate whether climate was the driving factor for these observed vegetation changes, we undertook a multiproxy study of lake sediment archives, using pollen, chironomid remains, diatoms, sediment geochemistry, and stable isotopes. We look at a series of sites on a transect from northern Vermont to southern Connecticut. This talk will focus on one site in southern New Hampshire, North Round Pond. Some questions we address in the study include: Did the “Little Ice Age” exist in New England and can it be documented by the study of proxy signals in lake sediments? Was climate the driving factor for vegetation changes seen in our study and in many sites across the northeast? Was the impact of European settlement superimposed on climate and vegetation changes that were already in motion? At North Round Pond, we see a decline in the relative abundance of beech and hemlock pollen starting at about 60 cm (approx. 1100 AD). Chironomid-inferred temperature shows a negative shift of about 2°C starting at this time and lasting until approx. 1860 AD. At the same time, cellulose-inferred d¹⁸O becomes more negative, suggesting that conditions became wetter during this period with less evaporative enrichment of ¹⁸O. These results indicate that conditions in New England during the Little Ice Age were cooler and wetter than at present. Preliminary data from the other study sites show similar trends. Chironomid-inferred temperature reconstructions are based on a surface calibration set using sites from New England and Atlantic Canada.