Advancing Palaeoclimate Reconstructions using Triple Oxygen Isotopes in Carbonates
Abstract
The challenge in predicting monsoon is difficult to overcome by relying on instrumental data from only the past few decades. Palaeomonsoon reconstructions help us understand and predict the sensitivity and response of monsoon to forcings on multi-decadal-centennial timescale. Numerous palaeomonsoon reconstructions based on oxygen-18 in speleothems have been done in India to investigate the drivers of Indian Summer Monsoon Rainfall (ISMR). However, it can be difficult to deconvolve the δ18O signal into individual components, including possible kinetic isotope effects, temperature, precipitation amount, moisture source and transport, which can lead to an overstated climatic signal. In such a case, the extent to which the variability in ISMR in the instrumental period reflects natural variability, still remains debatable. In this seminar, I will discuss how triple oxygen isotope systematics can provide a way to identify kinetic effects and delineate the influencing processes. I will present results from in-house setup that have resolved the existing theoretical-experimental gap and interlaboratory inconsistencies, crucial in standardising triple oxygen measurements in carbonates. I will also present preliminary investigations of paired speleothem-dripwater samples from Indian caves.
Short-lived isotope systematics to understand Hadean-Archean crust-mantle evolution in Indian cratons
Abstract
The evolution of crustal and mantle reservoirs in Archean cratons has been extensively investigated through conventional geochemical techniques for decades. However, these approaches are often limited by poor geochemical preservation and analytical challenges. Non-conventional, short-lived isotopes such as 182W and 142Nd provide robust temporal constraints on Hadean mantle extraction and hidden crustal reservoirs. This talk highlights the application of novel geochemical techniques to unravel the crust-mantle evolution of Indian cratons. Dr. Arathy Ravindran is doing her postdoctoral research work at the University of Cologne, Germany with a focus on isotope geochemistry. She carried out her previous postdoctoral positions at ETH Zurich, Switzerland and her doctoral research at University of Bern, Switzerland.
Detection of Microplastics in a Complex Matrix: A Case Study on Urban Road Dust
Abstract
Microplastics (MPs) are an emerging environmental pollutant, with urban road dust serving among major reservoir due to tyre and brake wear abrasion and atmospheric deposition. The heterogeneous composition of road dust poses significant challenges for isolating and identifying polymers. This presentation will discuss the application of Fourier Transform Infrared (FTIR) microscopy for the qualitative and quantitative analysis of MPs in urban dust samples.
Biogeochemical controls on dissolved micronutrient (Ni, Cu, Zn, Cd) distributions in the Equatorial Pacific Ocean
Abstract
The Equatorial Pacific Ocean (EPO) is among the most productive oceanic regions and is characterized by strong CO2 outgassing, playing a pivotal role in the global carbon cycle. Here, we present the distributions of micronutrients along the German GEOTRACES GP11 transect in the EPO during a developing El Niño. This study aims to assess the biogeochemical controls governing micronutrient distributions along the transect, which are critical for elucidating potential linkages between surface productivity and nutrient supply. Model estimates combined with observational constraints indicate that equatorial upwelling and strong zonal currents exert primary controls on micronutrient fluxes and biological uptake ratios. These findings have important implications for the bioavailability of micronutrients in the surface EPO under an increasing frequency of extreme El Niño and La Niña events, which modulate upwelling strength and Equatorial Undercurrent (EUC) intensity across the EPO. Overall, this study highlights the differential impacts of water mass mixing and vertical processes including, organic matter remineralization, particle scavenging, and benthic fluxes, on micronutrient distributions in the EPO and provides new insights into their inter-basin variability and biogeochemical cycling in the Pacific Ocean.
About the speaker:
Dr. Naman Deep Singh is a geochemist and completed his integrated BS-MS degree at the Indian Institute of Science Education and Research (IISER) between 2010 and 2015, followed by a Ph.D. at the Physical Research Laboratory from 2015 to 2020. He is currently working as a postdoctoral researcher at GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany. His research interests focus on understanding the biogeochemical cycling of trace metals in the ocean and their influence on biological ocean productivity and chemical weathering processes in terrestrial systems.