• Devendra Lal

      Articles written in Journal of Earth System Science

    • Marine biogeochemistries of Be and Al: A study based on cosmogenic10Be, Be and Al in marine calcite, aragonite, and opal

      Weiquan Dong Devendra Lal Barbara Ransom Wolfgang Berger Marc W Caffee

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      The geochemical behaviors of Be and Al in ocean waters have been successfully studied in recent years using natural, cosmogenic, radioactive10Be and26Al as tracers. The present day dissolved concentrations and distribution of the stable and radioactive isotopes of Be and Al in ocean waters have revealed their short residence times and appreciable effects of exchange fluxes at the coastal and ocean-sediment interfaces. It follows that concentrations of these particle-active elements must have varied in the past with temporal changes in climate, biological productivity and aeolian flux of continental detritus to the oceans. We therefore investigated the feasibility of extending the measurements of Be and Al isotope concentrations in marine systems to the 103–106 y BP time scale. We report here the discovery of significant amounts of intrinsic Be and Al in marine foraminiferal calcite and coral aragonite, and of Al in opal (radiolarians) and aragonite (coral), which makes it possible to determine10Be/Be and26Al/Al in oceans in the past. We also report measured10Be/9Be in foraminiferal calcite in Pacific Ocean cores, which reveal that the concentrations and ratios of the stable and cosmogenic isotopes of Be and Al have varied significantly in the past 30 ky. The implications of these results are discussed.

    • Climatic forcing before, during, and after the 8.2 Kyr B.P. global cooling event

      Devendra Lal William G Large Stephan G Walker

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      This paper attempts at full characterization of the unique global 8.2Kyr B.P. cooling event. Significant atmospheric cooling started during 9.5–8.5Kyr B.P. when the Sun was extremely quiet during three periods of ∼50–100 years. The flood of melt water in the N. Atlantic from glacial lakes during the demise of the Laurentide ice sheet, starting at ∼8.5$Kyr$ B.P., adds to the atmospheric cooling. Climatic forcing events occurred at 8.5Kyr B.P., at 8.2Kyr B.P. and finally at 8.06Kyr B.P., leading to concurrent increases or decreases in the atmospheric 𝛥14C levels, completely consistent with the climatic forcing proposed here.

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