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  • 2010-2014  (2)
  • 2005-2009  (1)
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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Quaternary Science Reviews 28 (2009): 1693-1709, doi:10.1016/j.quascirev.2009.04.005.
    Description: We use a series of tests to evaluate two competing hypotheses about the association of climate and vegetation trends in the northeastern United States over the past 15 kyrs. First, that abrupt climate changes on the scale of centuries had little influence on long-term vegetation trends, and second, that abrupt climate changes interacted with slower climate trends to determine the regional sequence of vegetation phases. Our results support the second. Large dissimilarity between temporally-close fossil pollen samples indicates large vegetation changes within 500 years across 〉4° of latitude at ca. 13.25-12.75, 12.0-11.5, 10.5, 8.25, and 5.25 ka. The evidence of vegetation change coincides with independent isotopic and sedimentary indicators of rapid shifts in temperature and moisture balance. In several cases, abrupt changes reversed long-term vegetation trends, such as when spruce (Picea) and pine (Pinus) pollen percentages rapidly declined to the north and increased to the south at ca. 13.25-12.75 and 8.25 ka respectively. Abrupt events accelerated other long‐term trends, such as a regional increase in beech (Fagus) pollen percentages at 8.5-8.0 ka. The regional hemlock (Tsuga) decline at ca. 5.25 ka is unique among the abrupt events, and may have been induced by high climatic variability (i.e., repeated severe droughts from 5.7-2.0 ka); autoregressive ecological and evolutionary processes could have maintained low hemlock abundance until ca. 2.0 ka. Delayed increases in chestnut (Castanea) pollen abundance after 5.8 and 2.5 ka also illustrate the potential for multi-century climate variability to influence species’ recruitment as well as mortality. Future climate changes will probably also rapidly initiate persistent vegetation change, particularly by acting as broad, regional-scale disturbances.
    Description: This work was supported by NSF grants to B. Shuman (EAR‐0602408; DEB‐0816731) and J. Donnelly (EAR‐0602380).
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Quaternary Research 75 (2011): 523-530, doi:10.1016/j.yqres.2011.01.006.
    Description: Sediment and ground-penetrating radar data from Davis Pond near the Hudson River valley reveal past droughts in a historically humid region that presently supplies water to millions of people in and around New York City. A minimum of eleven sandy paleoshoreline deposits in the lake date from 13.4-0.6 cal ka BP. The deposits span 1500 to 200 years between bracketing radiocarbon dates, and intrude into lacustrine silts up to 9.0 m below the modern lake surface in a transect of six cores. Three lowstands, ca. 13.4-10.9, 9.2 and 8.2 cal ka BP indicate low regional moisture balance when low temperatures affected the North Atlantic region. Consistent with insolation trends, water levels rose from ca. 8.0 cal ka BP to present, but five low stands interrupted the rise and are likely associated with ocean-atmosphere interactions. Similar to evidence from other studies, the data from Davis Pond indicate repeated multi-century periods of prolonged or frequent droughts super-imposed on long-term regional trends toward high water levels. The patterns indicate that water supplies in this heavily populated region have continuously varied at multiple time scales, and confirm that humid regions such as the northeastern USA are more prone to severe drought than historically expected.
    Description: We thank The Ocean and Climate Change Institute at Woods Hole Oceanographic Institution and NSF Earth System History program grants (EAR-0602380 to J. Donnelly and EAR-0602408 to B. Shuman) for supporting this research.
    Keywords: Lake level ; Northeastern USA ; Hydroclimate ; Holocene
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 3
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 4300–4307, doi:10.1002/2014GL060183.
    Description: Geophysical and sedimentary records from five lakes in Massachusetts reveal regionally coherent hydrologic variability during the Holocene. All of the lakes have risen since ~9.0 ka, but multicentury droughts after 5.6 ka repeatedly lowered their water levels. Quantified water level histories from the three best-studied lakes share 〉70% of their reconstructed variance. Four prominent low-water phases at 4.9–4.6, 4.2–3.9, 2.9–2.1, and 1.3–1.2 ka were synchronous across coastal lakes, even after accounting for age uncertainties. The droughts also affected sites up to ~200 km inland, but water level changes at 5.6–4.9 ka appear out of phase between inland and coastal lakes. During the enhanced multicentury variability after ~5.6 ka, droughts coincided with cooling in Greenland and may indicate circulation changes across the North Atlantic region. Overall, the records demonstrate that current water levels are exceptionally high and confirm the sensitivity of water resources in the northeast U.S. to climate change.
    Description: The National Science Foundation (EAR-0602408, EAR- 1036191, and DEB-0816731 to Shuman; EAR-0602380 to Donnelly) and the Woods Hole Oceanographic Institution, Ocean and Climate Change Institute (Donnelly) funded this research.
    Description: 2014-12-25
    Keywords: Holocene ; Paleohydrology ; Northeast U.S. ; Ground-penetrating radar ; Lake levels ; Drought
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Format: application/msword
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