• Sushant S Naik

      Articles written in Journal of Earth System Science

    • Influence of climatic teleconnections on the temporal isotopic variability as recorded in a firn core from the coastal Dronning Maud Land, East Antarctica

      Sushant S Naik Meloth Thamban A Rajakumar Witty D’Souza C M Laluraj Arun Chaturvedi

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      Ice and firn core studies provide one of the most valuable tools for understanding the past climate change. In order to evaluate the temporal isotopic variability recorded in ice and its relevance to environmental changes, stable isotopes of oxygen and hydrogen were studied in a firn core from coastal Dronning Maud Land, East Antarctica. The annual 𝛿18O profile of the core shows a close relation to the El Niño Southern Oscillation (ENSO) variability. The ENSO indices show significant correlation with the surface air temperatures and 𝛿18O values of this region during the austral summer season and support an additional influence related to the Southern Annular Mode (SAM). The correlation between the combined ENSO-SAM index and the summer 𝛿18O record seems to have been caused through an atmospheric mechanism. Snow accumulation in this region illustrates a decreasing trend with opposite relationships with 𝛿18O data and surface air temperature prior and subsequent to the year 1997. A reorganization of the local water cycle is further indicated by the deuterium excess data showing a shift around 1997, consistent with a change in evaporation conditions. The present study thus illustrates the utility of ice-core studies in the reconstruction of past climate change and suggests possible influence of climatic teleconnections on the snow accumulation rates and isotopic profiles of snow in the coastal regions of east Antarctica.

    • A comparison of Globigerinoides ruber calcification between upwelling and nonupwelling regions in the Arabian Sea

      Sushant S Naik Shital P Godad P Divakar Naidu V Ramaswamy

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      Shell weights of planktonic foraminifera species Globigerinoides ruber in the size range of 300–355 μm were measured from sediment traps in the western and eastern Arabian Sea which represent upwelling and non-upwelling conditions respectively. In the Western Arabian Sea Trap (WAST), G. ruber flux ranged from 33.3 to 437.3#/m2/day and shell weights ranged from 6.7 to 14.2 𝜇g. Whereas, in the Eastern Arabian Sea Trap (EAST), flux ranged from 0.7 to 164.6#/m2/day and shell weights ranged from 10.4 to 14.8 𝜇g. Shell weights of G. ruber versus flux showed significant correlation at both the sites which reveals that shell calcification mainly depends on optimal growth conditions. Though the WAST and EAST location have distinct difference in pCO2 and sea surface temperature (SST), the shell weights of G. ruber are similar in these two regions which suggest that surface water pCO2 and SST do not show dominant influence on shell calcification on a seasonal timescale.

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