Bharat Sharma

Dr. Bharat Sharma

Computational Sciences and Engineering, Oak Ridge National Laboratory, Oak Ridge, Florida, USA
orcid

Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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22 May 2023 in Biogeosciences
Verified
Journal Article
Open access
PDF file
Bharat SharmaBharat Sharma
Bharat Sharma
JKJitendra Kumar
Jitendra Kumar
AGAuroop R. Ganguly
Auroop R. Ganguly
Forrest M. HoffmanForrest M. Hoffman
Forrest M. Hoffman
Increasing surface temperature could lead to enhanced evaporation, reduced soil moisture availability, and more frequent droughts and heat waves. The spatiotemporal co-occurrence of such effects further drives extreme anomalies in vegetation productivity and net land carbon storage. However, the impacts of climate change on extremes in net biospheric production (NBP) over longer time periods are unknown. Using the percentile threshold on the probability distribution curve of NBP anomalies, we computed negative and positive extremes in NBP. Here we show that due to climate warming, about 88 % of global regions will experience a larger magnitude of negative NBP extremes than positive NBP extremes toward the end of 2100, which accelerate the weakening of the land carbon sink. Our analysis indicates the frequency of negative extremes associated with declines in biospheric productivity was larger than positive extremes, especially in the tropics. While the overall impact of warming at high latitudes is expected to increase plant productivity and carbon uptake, high-temperature anomalies increasingly induce negative NBP extremes toward the end of the 21st century. Using regression analysis, we found soil moisture anomalies to be the most dominant individual driver of NBP extremes. The compound effect of hotness, dryness, and fire caused extremes at more than 50 % of the total grid cells. The larger proportion of negative NBP extremes raises a concern about whether the Earth is capable of increasing vegetation production with a growing human population and rising demand for plant material for food, fiber, fuel, and building materials. The increasing proportion of negative NBP extremes highlights the consequences not only of reduction in total carbon uptake capacity but also of conversion of land to a carbon source.

16 June 2022 in Journal of Geophysical Research: Biogeosciences
Verified
Journal Article
Open access
Bharat SharmaBharat Sharma
Bharat Sharma
JKJitendra Kumar
Jitendra Kumar
NCNathan Collier
Nathan Collier
Auroop Ratan GangulyAuroop Ratan Ganguly
Auroop Ratan Ganguly
Forrest M. HoffmanForrest M. Hoffman
Forrest M. Hoffman
The increasing atmospheric carbon dioxide (CO2) mole fraction affects global climate through radiative (trapping longwave radiation) and physiological effects (reduction of plant transpiration). We use the simulations of the Community Earth System Model (CESM1‐BGC) forced with Representative Concentration Pathway 8.5 to investigate climate‐vegetation feedbacks from 1850 to the year 2300. Human‐induced land use and land cover change (LULCC), through biogeochemical and biogeophysical processes, alter the climate and modify photosynthetic activity. The changing characteristics of extreme anomalies in photosynthesis, referred to as carbon cycle extremes, increase the uncertainty of terrestrial ecosystems to act as a net carbon sink. However, the role of LULCC in altering carbon cycle extremes under business‐as‐usual (continuously rising) CO2 emissions is unknown. Here we show that LULCC magnifies the intensity, frequency, and extent of carbon cycle extremes, resulting in a net reduction in expected photosynthetic activity in the future. We found that large temporally contiguous negative carbon cycle extremes are due to a persistent decrease in soil moisture, which is triggered by declines in precipitation. With LULCC and global warming, vegetation exhibits increased vulnerability to hot and dry environmental conditions, increasing the frequency of fire events and resulting in considerable losses in photosynthetic activity. While most regions show strengthening of negative carbon cycle extremes, a few locations show a weakening effect driven by declining vegetation cover or benign climate conditions for photosynthesis. Increasing hot, dry, and fire‐driven carbon cycle extremes are essential for improving carbon cycle modeling and estimation of ecosystem responses to LULCC and rising CO2 mole fractions. Moreover, large aberrations in vegetation productivity represent potential and growing threats to human lives, wildlife, and food security.

1 November 2022
Verified
Conference Paper
Closed access
Bharat SharmaBharat Sharma
Bharat Sharma
JKJitendra Kumar
Jitendra Kumar
Auroop Ratan GangulyAuroop Ratan Ganguly
Auroop Ratan Ganguly
Forrest M. HoffmanForrest M. Hoffman
Forrest M. Hoffman
Rising atmospheric carbon dioxide due to human activities through fossil fuel emissions and land use changes have increased climate extremes such as heat waves and droughts that have led to and are expected to increase the occurrence of carbon cycle extremes. Carbon cycle extremes represent large anomalies in the carbon cycle that are associated with gains or losses in carbon uptake. Carbon cycle extremes could be continuous in space and time and cross political boundaries. Here, we present a methodology to identify large spatiotemporal extremes (STEs) in the terrestrial carbon cycle using image processing tools for feature detection. We characterized the STE events based on neighborhood structures that are three-dimensional adjacency matrices for the detection of spatiotemporal manifolds of carbon cycle extremes. We found that the area affected and carbon loss during negative carbon cycle extremes were consistent with continuous neighborhood structures. In the gross primary production data we used, 100 carbon cycle STEs accounted for more than 75% of all the negative carbon cycle extremes. This paper presents a comparative analysis of the magnitude of carbon cycle STEs and attribution of those STEs to climate drivers as a function of neighborhood structures for two observational datasets and an Earth system model simulation.

12 September 2025 in Transportation Research Record: Journal of the Transportation Research Board
Verified
Journal Article
Closed access
MRMaedeh Rahimitouranposhti
Maedeh Rahimitouranposhti
Bharat SharmaBharat Sharma
Bharat Sharma
MCMustafa Camur
Mustafa Camur
OOOlufemi A. Omitaomu
Olufemi A. Omitaomu
XLXueping Li
Xueping Li
Ensuring robustness and resilience in intermodal transportation systems is essential for the continuity and reliability of global logistics. These systems are vulnerable to various disruptions, including natural disasters and technical failures. Despite significant research on freight transportation resilience, investigating the robustness of the system after targeted and climate-change-driven disruption remains a crucial challenge. Drawing on network science methodologies, this study models the interdependencies within the rail and water transport networks and simulates different disruption scenarios to evaluate system responses. We use the data from the U.S. Department of Energy Volpe Center for network topology and tonnage projections. The proposed framework quantifies deliberate, stochastic, and climate-driven infrastructure failure, using higher resolution downscaled multiple Earth System Models’ simulations from Coupled Model Intercomparison Project Phase version 6. We show that the disruptions of a few nodes could have a larger impact on the total tonnage of freight transport than on network topology. For example, the removal of targeted 20 nodes can bring the total tonnage carrying capacity to 30% with about 75% of the rail freight network intact. This research advances the theoretical understanding of transportation resilience and provides practical applications for infrastructure managers and policymakers. By implementing these strategies, stakeholders and policymakers can better prepare for and respond to unexpected disruptions, ensuring sustained operational efficiency in transportation networks.

3 November 2025
Verified
Conference Paper
Open access
ESEvan Scherrer
Evan Scherrer
MAMelissa Ree Allen-Dumas
Melissa Ree Allen-Dumas
Bharat SharmaBharat Sharma
Bharat Sharma

9 September 2022 in EGUsphere
Verified
Preprint
Open access
PDF file
Bharat SharmaBharat Sharma
Bharat Sharma
JKJitendra Kumar
Jitendra Kumar
AGAuroop R. Ganguly
Auroop R. Ganguly
Forrest M. HoffmanForrest M. Hoffman
Forrest M. Hoffman
Rising atmospheric CO2 concentrations enhance vegetation growth through increased carbon fertilization and water-use efficiency. Terrestrial vegetation takes up more than one-quarter of global anthropogenic carbon emissions, and uptake is modulated by regional climate. Increasing surface temperature could lead to enhanced evaporation, reduced soil moisture availability, and more frequent droughts and heat waves. The spatiotemporal co-occurrence of such effects further drives extreme anomalies in vegetation productivity and net land carbon storage. However, the impacts of climate change on extremes in net biospheric production (NBP) over longer time periods are unknown. Here we show that due to climate warming, about 88 % of global regions will experience a larger magnitude of negative NBP extremes than positive NBP extremes toward the end of 2100, which accelerate the weakening of the land carbon sink. Our analysis indicates the frequency of negative extremes associated with declines in biome productivity was larger than positive extremes, especially in the tropics. While the overall impact of warming at high latitudes is expected to increase plant productivity and carbon uptake, high-temperature anomalies increasingly induce negative NBP TCEs toward the end of the 21st century. We found soil moisture anomalies as the most dominant individual driver of NBP extremes and the compound effect of hot, dry, and fire caused extremes at more than 50 % of the total grid cells. The larger proportion of negative NBP extremes raises a concern about whether the Earth is capable of increasing vegetation production with growing human population and rising demand for plant material for food, fiber, fuel, and building materials. The increasing proportion of negative NBP extremes highlights the consequences of not only reduction in total carbon uptake capacity but also of conversion of land to a carbon source.