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Tiwari, Manish

Palaeolimnological Records of Regime Shifts From Marine-To-Lacustrine System in a Coastal Antarctic Lake in Response to Post-Glacial Isostatic Uplift

Abstract Views :251 | PDF Views:93

Authors

Badanal Siddaiah Mahesh ¹, Abhilash Nair ¹, Anish Kumar Warrier ², Anirudha Avadhani ¹, Rahul Mohan ¹, Manish Tiwari ¹

Affiliations
1 National Centre for Antarctic and Ocean Research, Headland-Sada, Vasco-da-Gama 403 804, IN
2 Department of Civil Engineering, Manipal Institute of Technology, Manipal University, Manipal 576 104, IN

Source

Current Science, Vol 115, No 9 (2018), Pagination: 1679-1683

Abstract

Low altitude coastal lakes along the Antarctic margin often contain both marine and lacustrine sediments as a result of relative sea level changes due to deglaciation. The sediments also record changes in regional climate. A sediment core from a coastal lake in Larsemann Hills, East Antarctica, viz. Stepped Lake (Heart Lake), records distinct changes in C, N, C/N_{atomic ratio}, δ ¹³C_OM, δ ¹⁵N_OM and diatom abundance during the mid-Holocene (8.3 to 4.6 kyr BP). Lower values (C_org ~1%; C/N 8, ¹³C_OM ~ –18‰) during the early Holocene (8.3–4 kyr BP) are consistent with marine conditions, while higher values [C_org 6%; C/N 12; ¹³C_OM ~ –12‰) suggest a shift to lacustrine conditions (5.5–4.6 kyr BP). The diatom community shows similar shift with the major part of Holocene (8.3– 5.5 kyr BP) dominated by sea-ice and open-ocean diatoms while the core-top sections (5.5–4.6 kyr BP) transitions to lacustrine diatoms (Stauroforma inermis). These observations confirm that the basin was marine, and later became isolated as a result of postglacial isostatic uplift after 4.7 kyr BP.

Keywords

Diatoms, Holocene Climate, Larsemann Hills, Stable Isotopes, Sedimentary Organic Matter.

Full Text

References

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Preface

Evolution and Dynamics of the Denitrification in the Arabian Sea on Millennial to Million-Year Timescale

Abstract Views :223 | PDF Views:69

Authors

Shubham Tripathi ¹, Padmasini Behera ¹, Manish Tiwari ¹

Affiliations
1 National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco-da-Gama, Goa 403 804, IN

Source

Current Science, Vol 119, No 2 (2020), Pagination: 282-290

Abstract

Denitrification in the Arabian Sea is a vital process that provides feedback to global warming by releasing nitrous oxide to the atmosphere. Therefore, it is important to understand the evolution and dynamics of denitrification on different timescales. We present here the denitrification variability spanning the past ~600 thousand years (kyr). It is based on ~300 new measurements from IODP 355 Expedition. We compared the existing records of denitrification to understand the factors influencing the denitrification on various timescales. On glacial–interglacial timescale, we find stronger denitrification during interglacial and weaker denitrification during glacial periods. During the Holocene, we observe declining denitrification in the Western Arabian Sea in response to the reduced monsoon-induced productivity but find increasing denitrification in the Northeastern Arabian Sea due to reduced ventilation.

Keywords

Arabian Sea, Denitrification, Geochemistry, Monsoon, Oceanic Circulation, Palaeoceanography, Stable Isotopes.

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