The Dole Effect and Its Variations During the Last 130,000 Years As Measured in the Vostok Ice Core
GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 8, NO. 3, PAGES 363-376, SEPTEMBER 1994 The Dole effect and its variations during the last 130,000 years as measured in the Vostok ice core Michael Bender • and Todd Sowers 2 GraduateSchool of Oceanography,University of RhodeIsland, Kingston Laurent Labeyrie Centredes Faibles Radioactivites, Centre National de la RechercheScientifique, Commissariat a L'EnergieAtomique, Gif-sur- Yvette, France Abstract. We review the currentunderstanding of the Dole effect (the observeddifference between the •5180of atmospheric0 2 andthat of seawater)and its causes, extend the record of variationsin theDole effectback to 130kyr before present using data on the •5180 of 0 2obtained from studying the Vostok ice core(Sowers et al., 1993), anddiscuss the significanceof temporalvariations. The Dole effectreflects oxygenisotope fractionation during photosynthesis, respiration, and hydrologic processes (evaporation, precipitation,and evapotranspiration). Our bestprediction of the present-dayDole effect,+20.8 %0,is considerablylower thanthe observedvalue, + 23.5 %0,and we discusspossible causes of this discrepancy. During the past 130 kyr, the Dole effecthas been 0.05 %0lower thanthe present value, on average.The standarddeviation of the Dole effect from the meanhas been only _+0.2 %0,and the Dole effect is nearly unchangedbetween glacial maxima and interglacial periods. The smallvariability in theDole effect suggeststhat relative rates of primaryproduction in theland and marine realms have been relatively constant.Most periodicvariability in the Dole effectis in the precessionband, suggesting that changes in thisglobal biogeochemical term reflects variations in low-latitudeland hydrology and productivity or possiblyvariability in low-latitudeoceanic productivity. Introduction they can potentially be made to do so. Ice core reconstructionsof the concentrationsof bioactivegases in air Our understanding of the response of the biosphere to provide an integratedglobal signal which complementsthe Pleistoceneclimate change is actually quite limited.
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