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Harvard Forest Symposium Abstract 2005
- Title: Lake-sediment evidence for late Holocene climatic variability across southern New England
- Primary Author: Wyatt Oswald (Emerson College)
- Additional Authors: David Foster (Harvard University)
- Abstract:
High-resolution climatic proxy records reveal century-scale environmental variability during the last few thousand years, but the geographic coverage of such records is limited, and thus the spatial patterns of late Holocene changes in climate remain poorly understood. To better understand temporal and geographic variations in the climate of southern New England, we assembled a dataset comprised of 28 lake-sediment records, mainly from Massachusetts, but also from Connecticut and southern New Hampshire. All of these records, which were dated via Pb-210, C-14, and pollen data, exceed 1000 years in age, and most are older than 2000 years. Sediment organic content was estimated by measuring percent weight loss-on-ignition (LOI). Most of these records have down-core variations in LOI, and many are characterized by low values approximately 2000, 1500, 1000, and/or 500 years ago. This pattern is most prevalent at sites on Cape Cod and Martha’s Vineyard, and in northwestern and north-central Massachusetts. Analyses of modern lake sediments (Shuman, B. 2003. Journal of Paleolimnology 30: 371-385) illustrate an association between low LOI values and shallow water depth, which suggests that the intervals of low LOI in the subset of lakes in our dataset may reflect times of lower lake levels. In turn, this indicates that southern New England experienced periods of warm/dry climate during the late Holocene at approximately 500-year intervals, an interpretation that is consistent with the timing of warm periods in the oxygen isotope record from the Greenland ice sheet (Grootes, P.M. et al. 1993. Nature 366: 552-554).
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