• Meloth Thamban

      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.

    • Provenance and temporal variability of ice rafted debris in the Indian sector of the Southern Ocean during the last 22,000 years

      M C Manoj Meloth Thamban A Sahana Rahul Mohan Kotha Mahender

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      Ice rafted debris (IRD) records were studied in two sediment cores (SK200/22a and SK200/27) from the sub-Antarctic and Polar frontal regime of the Indian sector of Southern Ocean for their distribution and provenance during the last 22,000 years. The IRD fraction consists of quartz and lithic grains, with the lithic grains dominated by volcaniclastic materials. IRD content was high at marine isotope stage 2 but decreased dramatically to near absence at the Termination 1 and the Holocene. The concentration of IRD at glacial section of the core SK200/27 was nearly twice that of SK200/22a. Moreover, IRD were more abundant at the last glacial maxima (LGM) in SK200/27 with its peak abundance proceeding by nearly two millennia than at SK200/22a. It appears that an intensification of Antarctic glaciation combined with a northward migration of the Polar Front during LGM promoted high IRD flux at SK200/27 and subsequent deglacial warming have influenced the IRD supply at SK200/22a. Quartz and lithic grains may have derived from two different sources, the former transported from the Antarctic mainland, while the latter from the islands of volcanic origin from Southern Ocean. Sea-ice, influenced by the Antarctic Circumpolar Current is suggested to be a dominant mechanism for the distribution of lithic IRD in the region.

    • Role of debris cover to control specific ablation of adjoining Batal and Sutri Dhaka glaciers in Chandra Basin (Himachal Pradesh) during peak ablation season

      Parmanand Sharma Lavkush K Patel Rasik Ravindra Ajit Singh K Mahalinganathan Meloth Thamban

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      As part of the on-going annual mass balance measurements on Batal and Sutri Dhaka glaciers, observationswere made during peak ablation (August–September) season in 2013 to understand the responseof debris covered and clean-ice (debris free) glacier surface to melting processes. Though, both the Bataland Sutri Dhaka glaciers have almost similar geographical disposition, Batal shows extensive debriscover (90% of the ablation area), while the latter is free from debris (only 5% of the ablation area). Thethickness of debris in Batal glacier is inversely proportional to altitude, whereas Sutri Dhaka mostlyexperienced debris-free zone except snout area. Observation revealed that the vertical gradient of ablationrate in ablation area is contrastingly opposite in these two glaciers, reflecting significant control ofdebris thickness and their distribution over glacier surface on the ablation rates. While different thickness(2–100 cm) of debris have attenuated melting rates up to 70% of total melting, debris cover of 2 cm thickness has accelerated melting up to 10% of the total melting. Estimated melt ratio revealsthat about 90% of the ablation area has experienced inhibited melting in Batal glacier, whereas only lessthan 5% ablation area of Sutri Dhaka has undergone inhibited melting. Comparison of topographicalmaps of 1962 with successive satellite images of the area demonstrates a terminus retreat of 373 ± 33.5 mand 579 ± 33.5 m for Batal and Sutri Dhaka glaciers for the period 1962–2013, respectively.

    • Spatio-temporal variability of snow water equivalent over the Vestre Broggerbreen and Feiringbreen glaciers, Ny-Alesund, Svalbard

      Lavkush Patel Parmanand Sharma Meloth Thamban

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      Snow water equivalent (SWE) is important for understanding the hydrological significance of glaciers. In this study, the spatial and temporal variability in SWE and its impact over the Vestre Broggerbreen and Feiringbreen glaciers around Ny-Alesund in Svalbard (high Arctic) were investigated in the early snow season for the period 2012–2017. The physical properties like depth and density were measured directly in the field and spatial characteristics curvature, slope and aspect were extracted from the digital elevation model. The Vestre Broggerbreen (4.1 km$^{2}$) is a NE flowing glacier, situated around 3 km SW to Ny-Alesund village while the Feiringbreen (7.5 km$^{2}$) is a SW flowing glacier, situated around 14 km NE across the Kongsfjorden. The SWE for the studied period (2012–2017) varied from 141 to 1188 mm. The significant (R$^{2}$ = 0.97) correlation indicated a possible control of snow depth over SWE compared to altitude (R$^{2}$ = 0.65) and other spatial characteristics. The glaciers have experienced negative balance and lost a significant amount of ice ($\sim$4 m.w.e.) since 2012. The observations suggest that the increased liquid precipitation and temperature in the early snow season have reduced SWE over both these valley glaciers. The reduced SWE has also contributed to decreases in the mass balance of these glaciers.

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