Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Meloth Thamban ¹, C. M. Laluraj ¹, Sushant S. Naik ¹, Arun Chaturvedi ²

Affiliations
1 National Centre for Antarctic and Ocean Research, Headland Sada, Vasco-da-Gama, Goa - 403 004, IN
2 Geological Survey of India (Antarctica Division) NH-5P, N.I.T., Faridabad - 121001, IN

Abstract

Antarctic ice core records have provided unprecedented information on past climatic changes and forcing factors on decadal to millennial timescales. The glaciochemical and stable isotope records of a shallow ice core from the coastal Dronning Maud Land (East Antarctica) were used here to reconstruct the coastal Antarctic environmental variability during the past ~470 years. Sea salt ion data indicate a significant additional contribution of chloride ions compared to sea water values, possibly through atmospheric scavenging. The nitrate (NO₃ ^-) profile exhibit significant temporal shifts than that of the sulphate (SO₄ ^2-), with a major shift around 1750 AD. The changes in NO₃ ^- record are synchronous with the proxy record of solar activity ( ¹⁰Be profile from a South Pole ice core), suggesting enhanced NO₃ ^- values during periods of reduced solar activity like the Dalton Minimum (~1790-1830 AD) and Maunder Minimum (~1640- 1710 AD). The δ¹⁸O records reveal that the more negative V values were coeval with several events of increased NO₃ ^- concentrations, suggesting enhanced preservation of NO₃ ^- during periods of reduced air temperatures. The δ¹⁸O and δD records of the core also suggest significant short-term and long-tem variability with more negative values indicating relatively lower air temperatures prior to 1715 AD. The δ¹⁸O records also revealed a significant warming of 2.7°C for the past 470 years, with a warming of ~0.6°C per century.

Keywords

Glaciochemistry, Stable Isotope, Ice Core, Solar Activity, Dronning Maud Land, Antarctica.

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Rajesh Asthana ¹, Arun Chaturvedi ¹

Affiliations
1 Antarctica Division, Geological Survey of India, Faridabad-121001, IN

Abstract

The present study embodies the description of textural characteristics and quartz grain morphology (under SEM) of sediments occurring in three micro-environments on the polar ice sheet. Coarse to fine grained, largely ill-sorted sediments with a polymodal distribution reflect a varying magnitude in the velocity of the transporting medium. A dominant saltation population with little suspension and lack of rolling population is revealed by cumulative curves which suggests transportation of these supraglacial sediments by wind. The quartz grains bear two generations of mechanical textures and a third phase of chemical textures attributed to glacial and aeolian environments.

Keywords

Sedimentology, Supraglacial Sediments, Grain Size Analysis, Schinnacher Oasis, Antarctica.

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