20th Century Dust Lows and the Weakening of the Westerly Winds over the Tibetan Plateau – Geophysical Research Letters – B. Grigholm et al.
B. Grigholm1,*, P.A. Mayewski1, S. Kang2,3, Y. Zhang4,5, U. Morgenstern6, M. Schwikowski7, S. Kaspari8, V. Aizen9, E. Aizen9, N. Takeuchi10, K.A. Maasch1, S. Birkel1, M. Handley1 andS. Sneed1
1Climate Change Institute and School of Earth and Climate Sciences, University of Maine, Orono, Maine. 2State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, China. 3CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, China. 4Institute of Tibetan Plateau Research, Chinese Academy of Sciences, China. 5Joint Key Laboratory of Cryosphere and Environment, China. 6Institute of Geological and Nuclear Sciences, National Isotope Centre, New Zealand. 7Paul Scherrer Institute, Switzerland. 8Department of Geological Sciences, Central Washington University, Washington. 9Department of Geography, University of Idaho, Moscow, Idaho. 10Department of Earth Sciences, Graduate School of Science, Chiba University, Japan.
Understanding past atmospheric dust variability is necessary to put modern atmospheric dust into historical context and assess the impacts of dust on the climate. In Asia, meteorological data of atmospheric dust is temporally limited, beginning only in the 1950s. High-resolution ice cores provide the ideal archive for reconstructing pre-instrumental atmospheric dust concentrations. Using a ~500-year (1477-1982AD) annually resolved calcium (Ca) dust proxy from a Tibetan Plateau (TP) ice core, we demonstrate the lowest atmospheric dust concentrations in the past ~500 years during the latter 20th century. Declines in late 19th-20th century Ca concentrations significantly correspond with regional zonal wind trends from two reanalysis models, suggesting that the Ca record provides a proxy for the westerlies. Twentieth century warming and attendant atmospheric pressure reductions over northern Asia have potentially reduced temperature/pressure gradients resulting in lower zonal wind velocities and associated dust entrainment/transport in the past ~500 years over the TP.