P2C2: Seasonal Dynamics of the Indo-Asian Monsoon during Deglaciations

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This projects aims to better constrain the seasonal behavior of Indo-Asian monsoon rainfall and related atmospheric dynamics (e.g. the jet stream) during climate transitions at the end of both the last and penultimate ice ages. The researchers will use recently developed methods for ion microprobe analysis to measure oxygen isotope ratios (delta18-Oxygen) recorded in the calcite mineral structure of speleothems at seasonal resolution. The speleothem delta18-Oxygen values record changes in past rainfall amount, source, and seasonality that are preserved as the speleothem grows, generating a record of past rainfall changes that can span tens to hundreds of thousands of years. Studies of past changes in precipitation are important because they potentially provide valuable insight on the fundamental controls and potential response of rainfall during climate transitions.The research team will analyze speleothems from Yemen and Israel to complement seasonal-resolution analyses from northeastern China. These samples represent a component of atmospheric circulation over Asia, each with an important seasonal component: the Westerlies (Israel), Indian Monsoon (Yemen), and East Asian Monsoon (China). Additionally, the team will to use global climate model simulations (i.e., Community Climate System Model version 3, TraCE-21K Community Atmosphere Model version 3) of rainfall delta18-Oxygen to assess the level of coherence between modeled and observed seasonal rainfall patterns across Asia during key climatic periods that followed the last two ice ages. The team will model a suite of seven diagnostic time-slices from these two periods when large changes in monsoon rainfall, including during a warming event ~11,500 years ago when an abrupt decadal-scale change may have occurred.The Broader Impacts involve supporting two early career scientists in research that could help improve the understanding of the timing and monsoonal rainfall. The Impacts also include participating in outreach programs with the UW-Madison Geology Museum.