Research Projects

This project will investigate the long-term variability and abrupt shifts of the Indian Summer Monsoon (ISM) using proxy records of water isotopes and climate model simulations. We will also study changes in monsoon water vapor sources under climate change scenarios and its effects on the isotope ratios of precipitation, to aid more accurate interpretations of climate records. The ISM is crucial for the livelihoods of billions in the Indian subcontinent. Observations suggest intensification of monsoon precipitation and increases in extremes, likely due to anthropogenic climate change. Further, studies show that climate systems may exhibit sudden or irreversible shifts under climate change, highlighting the potential for abrupt changes in the monsoon system. However, uncertainties about future projections persist despite advancements in Earth system modeling. Hence, paleoclimate studies are vital as they provide insights into past climate variability and help study monsoon response to climate factors. The ISM has experienced many abrupt shifts in the past, coinciding with major climate events in high-latitudes. Hence, it is crucial to identify the monsoon's variability and potential abrupt shifts. Stable isotopes of hydrogen and oxygen in water trace the hydrological cycle, offering insights into global hydrology. In the tropics, the isotope ratios in precipitation are observed to be inversely proportional to the amount of precipitation, which is used for monsoon reconstructions. The water isotopic ratios derived from the sedimentary cores, cave stalagmites, tree rings are used to reconstruct the South Asian monsoon. However, these proxy records are subject to limitations such as uncertainty in climate controlling factors of isotopic composition and geographical distribution. Recent studies suggest that water isotope ratios need not dominantly represent the precipitation amount, and are affected by moisture sources and circulation. However, the assessment of different moisture sources and their isotope signatures was not possible until recently due to the lack of modeling resources with moisture tracking. The recent model iCESM introduces a "water tagging" method in the model along with water isotope tracking, enabling the model to track the evaporative origins and pathways of water and isotopes, offering unprecedented detail on the hydrological cycle. To comprehensively understand long-term monsoon variability, we propose a study integrating direct-water isotope modeling and paleoclimate records. We will analyze the long term variability and abrupt shifts in monsoons from available water isotope proxy data from the monsoon regions, focusing on the ISM. Further, using direct proxy-climate modeling and climate model-intercomparisons we will study the factors, especially changes in water vapor sources affecting the monsoon and the water isotope proxies.