PP006-06
Hydroclimate Footprint Accompanying Asian Monsoon Water Isotope during Last Deglaciation

Monday, 7 December 2020: 07:20
Virtual
Zhengyu Liu, Ohio State University Main Campus, Columbus, OH, United States, Chengfei He, Ohio State University, Geography, Columbus, United States, Bette L Otto-Bliesner, National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, Boulder, CO, United States, Esther C Brady, National Center for Atmospheric Research, Boulder, Boulder, CO, United States, Chenyu Zhu, Peking University, Department of Atmospheric and Oceanic Sciences, School of Physics, Beijing, China, Robert A Tomas, NCAR, Boulder, CO, United States, Peter U Clark, Oregon State University, Corvallis, OR, United States, Jiang Zhu, Univ Wisconsin Madison, Madison, WI, United States, Alexandra Jahn, University of Colorado Boulder, Atmospheric and Oceanic Sciences and Institute of Arctic and Alpine Research (INSTAAR), Boulder, CO, United States, Sifan Gu, University of Wisconsin Madison, Madison, WI, United States, Jiaxu Zhang, Los Alamos National Laboratory, Los Alamos, NM, United States, Jesse M. Nusbaumer, National Center for Atmospheric Research, Boulder, CO, United States, David Noone, University of Auckland, Department of Physics, Auckland, New Zealand, Hai Cheng, University of Minnesota, Department of Earth Sciences, Minneapolis, MN, United States, Yongjin Wang, Nanjing Normal University, Dept. of Geography, Nanjing, China, Mi Yan, Nanjing Normal University, Nanjing, China and Yuntao Bao, Ohio State University, Columbus, Afghanistan
Recorded Presentation
Abstract:
The development of well-dated, high-resolution oxygen-isotope speleothem (δ18O of calcite, or δ18Oc) records has significantly improved our understanding of past changes of the pan-Asian summer monsoon (AM). Although these δ18Oc records are generally regarded as proxies of “monsoon intensity,” the climatic processes underlying this interpretation remain widely debated, particularly in their representation of large-scale AM hydroclimate. Some studies have interpreted the δ18Oc variability as related to local rainfall changes, with depleted δ18Oc corresponding to increased rainfall due to the amount effect. In contrast, other studies have suggested that the δ18Oc variability, particularly over the East Asian Monsoon (EAM), is caused by upstream rainfall depletion, with the corresponding rainfall response associated with changing seasonality, moisture transport, westerly jet, or no local rainfall change. These hypotheses, however, are largely based on highly idealized model experiments that are unable to reproduce the full extent of the observational variability. Here we show, using an isotope-enabled Earth system model in transient experiments, that the widespread AM δ18Oc signal during the last deglaciation (20-11 ka) is accompanied by a spatially coherent, yet heterogeneous, hydroclimate footprint across the AM region as a response mainly to insolation and meltwater forcing. With a northward migration of the westerly jet and enhanced southwesterly monsoon wind, the footprint that accompanys a widespread δ18Op depletion exhibits increased rainfall from South Asia to northern China, but decreased rainfall in southern China.
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