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1.
Akinori Takeuchi Angela J. Goodwin Bryan G. Moravec Peter B. Larson C. Kent Keller 《Quaternary Research》2009,72(2):198-206
Large-scale atmospheric circulation patterns determine the quantity and seasonality of precipitation, the major source of water in most terrestrial ecosystems. Oxygen isotope (δ18O) dynamics of the present-day hydrologic system in the Palouse region of the northwestern U.S.A. indicate a seasonal correlation between the δ18O values of precipitation and temperature, but no seasonal trends of δ18O records in soil water and shallow groundwater. Their isotope values are close to those of winter precipitation because the Palouse receives 75% of its precipitation during winter. Palouse Loess deposits contain late Pleistocene pedogenic carbonate having ca. 2 to 3‰ higher δ18O values and up to 5‰ higher carbon isotope (δ13C) values than Holocene and modern carbonates. The late Pleistocene δ18O values are best explained by a decrease in isotopically light winter precipitation relative to the modern winter-dominated infiltration. The δ13C values are attributed to a proportional increase of atmospheric CO2 in soil CO2 due to a decrease in soil respiration rate and 13C discrimination in plants under much drier paleoclimate conditions than today. The regional climate difference was likely related to anticyclonic circulation over the Pleistocene Laurentide and Ice Sheet. 相似文献
2.
Brad E. Rosenheim Peter K. Swart Philippe Willenz 《Geochimica et cosmochimica acta》2009,73(18):5308-5319
A revised calibration is presented relating the oxygen isotope composition of the aragonite-secreting sclerosponge Ceratoporella nicholsoni, oxygen isotope composition of seawater, and ambient water temperature. This new relationship has been obtained using high-resolution δ18O data measured in sclerosponges from the Bahamas and Jamaica compared to ambient temperature measurements and δ18O values of seawater from the two locations, both measured and published. New data improve an existing calibration which was determined using measurements of salinity rather than directly measured δ18O values of the seawater and was composed of measurements from different species of sclerosponge and other aragonite-secreting organisms. The updated calibration (n = 12, r2 = 0.95) is:
T(°C)=16.1(±3.1)-[6.5(±1.1)](δarag-δsw),