Abstract
Long-term, large-scale perspectives are necessary for understanding climate variability and its effects on ecosystems and cultures. Tree ring records of the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) have documented major hydroclimatic variability during the last millennium in the American West, but fewer continuous, high-resolution hydroclimate records of the MCA-LIA period are available for eastern North America, particularly during the transition from the MCA to the LIA (ca. A.D. 1250–1400). Diatoms (micro-algae with silica cell walls) in sediment cores from three Adirondack (NY, USA) lakes and a hiatus in a wetland peat deposit in the Adirondack uplands provide novel insights into the late Holocene hydroclimate history of the Northeast. These records demonstrate that two of the region’s most extreme decadal-scale droughts of the last millennium occurred ca. A.D. 1260–1330 and ca. A.D. 1360–1390 during a dry-wet-dry (DWD) oscillation in the Adirondacks that contributed to forest fires and desiccation of wetlands in New York and Maine. The bimodal drying was probably related to more extreme droughts farther west and coincided with major events in Iroquoian and Abenaki cultural history. Although the causes of the DWD oscillation in the Adirondacks remain uncertain, changing sea-surface temperatures and solar variability are likely to have played a role.
Highlights
Paleoclimate reconstructions of the last millennium indicate generally warmer conditions in much of North America during the Medieval Climate Anomaly (MCA), which is commonly defined as the period between A.D. 950 and A.D. 1250 [1], followed by cooler conditions during the Little Ice Age (LIA) ca
We demonstrate that the dry-wet-dry (DWD) oscillation was temporally linked to more extreme "megadroughts" [17, 26] farther west, potentially influenced by multiple climatic forcing mechanisms, and contemporaneous with significant events in North American cultural prehistory
These dates are less firmly anchored in time than those from most tree rings records, we are confident that ancient carbon offsets are not significant in Wolf Lake because equivalent dates were previously obtained for pollen and bulk sediment samples there [5], and the similar ages and durations of similar excursions in %P at all three lakes in addition to the hiatus at Bloomingdale Bog strongly suggest that the excursions were contemporaneous
Summary
Paleoclimate reconstructions of the last millennium indicate generally warmer conditions in much of North America during the Medieval Climate Anomaly (MCA), which is commonly defined as the period between A.D. 950 and A.D. 1250 [1], followed by cooler conditions during the Little Ice Age (LIA) ca. Reconstructions of regional moisture balance from the Northeast, defined here as the eastern Great Lakes region through New England, are available from upstate New York [5,6,7,8], southern Ontario [9] and New England [10,11,12,13,14,15,16,17], they are much less numerous than in the American West where more long-lived, drought-sensitive.
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