Regional climate model experiments to investigate the Asian monsoon in the Late Miocene

Abstract

Abstract. The Late Miocene (11.6-5.3 Ma) is a crucial period in the history of the Asian monsoon. Significant changes in the Asian climate regime have been documented for this period, which saw the formation of the modern Asian monsoon system. However, the spatiotemporal structure of these changes is still ambiguous, and the associated mechanisms are debated. Here, we present a simulation of the average state of the Asian monsoon climate for the Tortonian (11-7 Ma) using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1 • × 1 • ) and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our regional Tortonian run shows a stronger-than-present East Asian winter monsoon wind as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered present-day northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. Precipitation decreases in northern China and northern India, but increases in southern China, the western coast and the southern tip of India. This can be attributed to the changes in both the regional topography (e.g. the lower northern Tibetan Plateau) and the global climate conditions (e.g. the higher sea surface temperature). The spread of dry summer conditions over northern China and northern Pakistan in our Tortonian run further implies that the monsoonal climate may not have been Correspondence to: H. Tang (hui.tang@helsinki.fi) fully established in these regions in the Tortonian. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better characterizes the convective activity and its response to regional topographical changes. It therefore provides a useful and compared to global models, a complementary tool to improve our understanding of the Asian monsoon evolution in the Late Miocene.

Climatically forced moisture supply, sediment flux and pedogenesis in Miocene mudflat deposits of south‐east Kazakhstan, Central Asia

“…Results from climate modelling with Miocene boundary conditions and lower than present topography suggest significant warming in Inner Asia compared to today (Henrot et al ., ; Tang et al ., ). Climate warming is most pronounced in the winter with more zonal climate and increased moisture supply by westerly winds.…”

“…Topographic map of Inner Asia showing present‐day mountain ranges together with results of a regional Miocene climate simulation with lower topography than at present (Tang et al ., ). Also shown are localities with Miocene palaeoclimate proxy data from literature and this study (Sun et al ., , ; Miao et al ., ; Tang et al ., ; Charreau et al ., ; Caves et al ., ).…”

Late Miocene–Pliocene Paleoclimatic Evolution Documented by Terrestrial Mollusk Populations in the Western Chinese Loess Plateau

“…However another quantitative reconstruction from plant fossil records yielded contrasting results, indicating that records of both temperature and precipitation from north China exhibit no significant difference between the western and eastern regions during the Miocene, suggesting that the monsoon climate did not commence or intensify at that time [35]. Regional climate model experiments also reveal that during the Late Miocene, from 11–7 Ma, the monsoonal climate may not have been fully established in various Asian regions, including northern China [36]; and this finding is contrary to that of numerous previous studies of the EA monsoon which suggest that it was initiated around the time of the Oligocene/Miocene boundary [37]–[39].…”

Historical Monitoring of Shoreline Changes in the Cua Dai Estuary, Central Vietnam Using Multi-Temporal Remote Sensing Data

“…The tidal regime of the study area was assessed through water level data at the closest tide The wind is an important factor in wave formation, causing shoreline erosion. According to Tang (2009), the wave height depends generally on the wind direction at the shore area, with large waves occurring during either the northeast monsoons or the flowing of easterly winds [28]. The annual activity of the northeast monsoon wind makes the coastal current stronger in the direction from north to south.…”