Combined records from a stalagmite from Barbados and from lake sediments in Haiti reveal variable seasonality in the Caribbean between 6.7 and 3 ka BP |
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| Institution: | 1. University of Maryland Center for Environmental Science Chesapeake Biological Laboratory, 146 Williams St., Solomons, MD 20688, United States;2. NOAA Earth Systems Research Laboratory, 325 Broadway, R/PSD1 Boulder, CO 80305, United States;3. School of Marine and Atmospheric Sciences, 107 Dana Hall, Stony Brook University, Stony Brook, NY 11974-5000, United States;1. WiscSIMS, Department of Geoscience, University of Wisconsin, 1215W Dayton St., Madison, WI 53706, USA;2. Geological Survey of Israel, 30 Malchei Israel St., Jerusalem 95501, Israel;3. The Institute of Earth Sciences, The Hebrew University, Givat Ram, Jerusalem 91904, Israel |
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| Abstract: | The growth of a well-dated stalagmite from Barbados records high infiltration rates into the karst aquifer and hence increased rainfall intensity between 6.7 and 3 ka BP in agreement with records from Lake Miragoane, Haiti Hodell et al., 1991. Reconstruction of the Caribbean climate change over the past 10,500 years. Nature 352, 790–793], mainly reflecting the insolation maximum of the Northern Hemisphere. Both the lake record and the stable isotope record of the stalagmite reveal additional centennial variability of recharge. High oxygen isotope values in stalagmite calcite, corresponding to reduced recharge, are synchronous with periods of lower stable isotope values recorded in Lake Miragoane ostracods, previously attributed to enhanced precipitation. Accordingly, periods of increased recharge in Barbados correspond to 18O-enriched isotope values of ostracods, which were attributed to higher evaporation/precipitation ratios in the lakes. We ascribe this apparent discrepancy to changes in seasonality, i.e., winter periods of reduced temperature and relative humidity following summer months of increased precipitation. At present, such climate conditions occur during periods of enhanced Northern Atlantic Oscillation (NAO+). If enhanced seasonality is a consequence of a NAO+ situation, the apparent discrepancy of high isotope values in lakes (previously attributed to droughts) can be reconciled with lower winter temperatures in the lakes. Further, the correlation of solar intensity (derived from 14C and 10Be) with the isotopic signals recorded in the lacustrine sediments suggests a solar forcing of the NAO during the mid Holocene. |
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