A principal method for studying past hydroclimatic change is the reconstruction of paleo-lake levels. Here, we provide high-resolution lake-level records from New Long Pond and Rocky Pond in southeastern Massachusetts, which each contain evidence for multiple, sub-centennial-to-millennial scale low stands during the transition between the Late Pleistocene (15.0 ka) and Middle Holocene (ca 7.0 ka). Data from New Long Pond also demonstrate sedimentary evidence for a drop in water levels in the early to mid AD 20th century, when long-term trends in instrumental data show lower-than-average precipitation in the northeastern United States. Local data show the most precipitous declines in precipitation and groundwater levels are concurrent with the most severe drought in the AD 1960s, which occurred during a period of low sea-surface temperatures in the western North Atlantic. Ground penetrating radar and sediment core data indicate five intervals with numerous paleo-shoreline deposits between ca 15.0 and 7.0 ka, similar to the layer deposited in the AD 1960s. Many of the intervals of low lake levels coincide with proposed meltwater release events or abrupt climate oscillations in the circum North Atlantic. For example, we document at least three low stands during the Younger Dryas (12.9-11.6 ka) and in association with the "9.2" and "8.2" ka events. The combined evidence of (1) concurrent paleo-droughts in southeastern New England with documented North Atlantic abrupt cooling events and (2) recent drought with the modern association of low sea-surface temperatures indicates that freshening and cooling of the western North Atlantic is a viable mechanism for decreasing moisture within the region. Large-scale changes in seasonality and ice sheet extent also may have increased the susceptibility of the northeast to dry conditions triggered by changes in the North Atlantic.
Bibliographical noteFunding Information:
The National Science Foundation (NSF-ESH 0602408 to Shuman and Donnelly) and the Woods Hole Oceanographic Institution, Ocean and Climate Change Institute (to Donnelly) funded this research. Many people contributed to the laboratory and field work of this project: J. Berman, K. Boldt, W. D'Andrea, Z. Fjeldheim, M. Gomes, A.V. Henderson and H. Henderson, J. Hou, Z. Klaus, S. LaRose, G. and A. Newby, R. Sorell, J. Tierney, M. Toomey, N. Trenholm, T. Webb III, and J. Woodruff. We thank Lynn Carlson for expert GIS work, and S. Haggerty, T. Huguenin, S. Maier and the expertise of the Natural Heritage and Endangered Species Program (Massachusetts Division of Fisheries and Wildlife/Natural Heritage network), Westborough, Massachusetts for plant identifications. Finally, we kindly thank our two reviewers for their time and comprehensive comments, which greatly improved this manuscript.
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