Strong winter monsoon wind causes surface cooling over India and China in the Late Miocene
H. Tang1, J. T. Eronen1,2, A. Kaakinen1, T. Utescher3, B. Ahrens4, and M. Fortelius11Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland 2Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325 Frankfurt am Main, Germany 3Senckenberg Research Institute, Frankfurt Main; Steinmann Institute, University of Bonn, Nussallee 8, 53115 Bonn, Germany 4Institute for Atmospheric and Environmental Sciences, Goethe University, Altenhoeferallee 1, 60438, Frankfurt am Main, Germany
Received: 26 Nov 2014 – Accepted for review: 29 Dec 2014 – Discussion started: 23 Jan 2015
Abstract. Modern Asian winter monsoon characterised by the strong northwesterly wind in East Asia and northeasterly wind in South Asia, has a great impact on the surface temperature of the Asian continent. Its outbreak can result in significant cooling of the monsoon region. However, it is still unclear whether such an impact existed and is detectable in the deep past. In this study, we use temperature reconstructions from plant and mammal fossil data together with climate model results to examine the co-evolution of surface temperature and winter monsoon in the Late Miocene (11–5 Ma), when a significant change of the Asian monsoon system occurred. We find that a stronger-than-present winter monsoon wind might have existed in the Late Miocene due to the lower Asian orography, particularly the northern Tibetan Plateau and the mountains north of it. This can lead to a pronounced cooling in southern China and northern India, which counteracts the generally warmer conditions in the Late Miocene compared to present. The Late Miocene strong winter monsoon was characterised by a marked westerly component and primarily caused by a pressure anomaly between the Tibetan Plateau and Northern Eurasia, rather than by the gradient between the Siberian High and the Aleutian Low. As a result, the close association of surface temperature with winter monsoon strength on inter-annual scale as observed at present may not have established in the Late Miocene.
Tang, H., Eronen, J. T., Kaakinen, A., Utescher, T., Ahrens, B., and Fortelius, M.: Strong winter monsoon wind causes surface cooling over India and China in the Late Miocene, Clim. Past Discuss., 11, 63-93, doi:10.5194/cpd-11-63-2015, 2015.