Paleoclimate Group: Ongoing Projects

Project Code and Sponsoring Agency

Project Title

MLP-6504-28 (NS)
Main Lab Project; CSIR-NGRI

High-resolution Paleoceanographic and Paleoclimatic studies using isotopic and trace elemental proxies of corals, speleothems and marine sediments

PSC 0204; WP:3.3 (NS)
INDEX: CSIR12th Five Year Plan

Paleoclimatic studies during the last 25 ka using isotopic and trace elemental proxies from corals, speleothems and marine sediments

PSC 0205; WM:2.8 (NS)
SHORE: CSIR12th Five Year Plan

Determination of precise chronostratigraphy in the deep-sea sediment cores
from the Bay of Bengal

Staff

S.No

Name of the Personnel

Designation

ID. No.

1

Netramani Sagar

Scientist and Head

1099

2

K. Venkatesham

Technical Officer

1024

3

G. Suseela

Technical Officer

1048

4

Waseem Raza

Technical Assistant

1127

5

Md. Anwar

Multi Tasking Staff

931

Instrumentation Facilities

S. No.

Research Instruments with group’s Responsibility

Operated by

1

Isotope Ratio Mass Spectrometer (IRMS) coupled with Kiel IV Carbonate Device

Waseem Raza, and
K. Venkatesham

2

Isotope Ratio Mass Spectrometer (IRMS) coupled with Elemental Analyzer (EA)

Waseem Raza

3

Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES)

Netramani Sagar, and
K. Venkatesham

4

Particle Size Analyzer

K. Venkatesham

5

Milipore Unit, Works related to foraminifera (separation, splitting, etc.)

G. Suseela

Recent Research Activities

High-resolution historic/ paleoclimatic studies using Scleractinian Corals from the Lakshadweep Archipelago

High-resolution Sr/Ca ratios in a Porites lutea coral from Lakshadweep Archipelago, southeast Arabian Sea: An example from a region experiencing steady rise in the reef temperature
(Sagar et al., 2016, JGR Oceans)

In this paper, we present the first record of Sr/Ca variability in a massive Porites lutea coral from the Lakshadweep Archipelago, Arabian Sea. The annual mean sea surface temperature (SST) in this region and the surrounding areas has increased steadily in the recent past. During some major El Niño events, SSTs are even higher, imposing additional thermal-stress on corals, episodically leading to coral bleaching. We infer from the coral-Sr/Ca record (1981–2008) that during some of these events high and persistent SSTs lead to a dampening of the temperature signal in coral-Sr/Ca, impairing the coral’s ability to record full scale warming. Thus, coral-Sr/Ca may provide a history of past El Niño Southern-Oscillation (ENSO) induced thermal stress episodes, which are a recurrent feature also seen in cross-spectral analysis between coral Sr/Ca and the Nino3.4 index. Despite the impact of episodical thermal-stress during major El Niño events, our coral proxy faithfully records the seasonal monsoon-induced summer cooling on the order of _2.38C. Calibration of coral-Sr/Ca with instrumental grid-SST data shows significant correlation to regional SST and monsoon variability. Hence, massive Porites corals of this region are highly valuable archives for reconstructing long term changes in SST, strongly influenced by monsoon variability on seasonal scales. More importantly, our data show that this site with increasing SST is an ideal location for testing the future effects of the projected anthropogenic SST increase on coral reefs that are already under thermal-stress worldwide.

paleo1

(a) Location map of the studied coral site at the lagoon of Kavaratti (*) Island, Lakshadweep Archipelago, Arabian Sea. (b) The Lakshadweep High (LH) and (c) Low (LL)

Figure4_JGRO.tif

(a) Local summer (March, April, May) average SST from Reynolds OISST with coral-Sr/Ca (summer average: March, April, May). The bright orange bars represent the positive temperature anomaly in the Nino3.4 region. Blue vertical bars represent the positive Sr/Ca anomalies (in the years 1987, 1998, and 2003). The light-green vertical bars represent the negative Sr/Ca anomalies (in the years 1983, 1989, and 1990). The year 1998 marks the highest summer-average SST of 30.4 ˚C. (b) HotSpot values (red vertical bars) calculated from Reynolds OISST monthly data sets. The year 1998 has the highest HotSpot value (>1 ˚C). The maximum monthly mean and the bleaching threshold SST of this region is 30.1 and 31.1 ˚C, respectively. 

Reconstructing Indian Monsoon Rainfall using Marine Sediments recovered during the International Ocean Discovery Program Expedition 353: Indian Monsoon Rainfall

  (Participation by Netramani Sagar during 29 Dec 2014 – 29 Jan 2015 on board the JOIDES Resolution in the Bay of Bengal and Andaman Sea)

https://iodp.tamu.edu/scienceops/expeditions/maps/indian.jpg

Red circles :               Places of drilling the marine sediments
Yellow circles:           Path showing the journey of the scientific research and drilling vessel; JOIDES Resolution
(Map credit: IODP)

Outreach Activities

  •   Every year: Conduction summer training for Masters students from ISM-Dhanbad, Banaras Hindu University, IISER Kolkata, and other institute (one-two in each year).
  • 2016: Delivered a lecture to XIIth standard students of DPS Nacharam on Paleoclimate studies undertaken by the group.