Paleoclimatic estimation reveals a weak winter monsoon in southwestern China during the late Miocene: Evidence from plant macrofossils

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.

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Late Miocene climate cooling and intensification of southeast Asian winter monsoon

Nature Communications ◽

10.1038/s41467-018-03950-1 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 46

Author(s):

Ann E. Holbourn ◽

Wolfgang Kuhnt ◽

Steven C. Clemens ◽

Karlos G. D. Kochhann ◽

Janika Jöhnck ◽

...

Keyword(s):

Late Miocene ◽

Southeast Asian ◽

Winter Monsoon ◽

Asian Winter Monsoon ◽

Climate Cooling

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The intensification of the East Asian winter monsoon contributed to the disappearance of Cedrus (Pinaceae) in southwestern China

Quaternary Research ◽

10.1016/j.yqres.2013.07.001 ◽

2013 ◽

Vol 80 (2) ◽

pp. 316-325 ◽

Cited By ~ 22

Author(s):

Tao Su ◽

Yu-Sheng (Christopher) Liu ◽

Frédéric M.B. Jacques ◽

Yong-Jiang Huang ◽

Yao-Wu Xing ◽

...

Keyword(s):

East Asian Winter Monsoon ◽

East Asian ◽

Winter Monsoon ◽

Southwestern China ◽

Natural Forests ◽

Climate Data ◽

Late Pliocene ◽

Asian Winter Monsoon ◽

Western Yunnan ◽

Fossil Records

Climate change during the Quaternary played an important role in the distribution of extant plants. Herein, cone scales of Cedrus (Pinaceae) were uncovered from the Upper Pliocene Sanying Formation, Longmen Village, Yongping County of Yunnan Province in southwestern China. Detailed comparisons show that these fossils all belong to the genus Cedrus (Pinaceae), and a new species is proposed, Cedrus angusta sp. nov. This find expands the known distribution of Cedrus during the Late Pliocene to Yunnan, where the genus no longer exists in natural forests. Based on the analysis of reconstructed Neogene climate data, we suggest that the intensification of the East Asian winter monsoon during the Quaternary may have dramatically increased seasonality and given rise to a much drier winter in Yunnan. Combined with information on Cedrus fossil records and its seed physiology, we conclude that the intensification of a drier climate after the Late Pliocene may have prevented the survival of Cedrus seedlings, leading to the eventual disappearance of Cedrus in western Yunnan. This study indicates that the topography in southwestern China acted as a vital refuge for many plants during the Quaternary, but that other species gradually disappeared due to the intensification of the monsoonal climate.

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Floristic divergence of the evergreen broad-leaved forests in Yunnan, southwestern China

Phytotaxa ◽

10.11646/phytotaxa.393.1.1 ◽

2019 ◽

Vol 393 (1) ◽

pp. 1

Author(s):

HUA ZHU

Keyword(s):

Late Miocene ◽

Floristic Composition ◽

Southwestern China ◽

Geological History ◽

Forest Types ◽

Broad Leaved Forest ◽

Global Cooling ◽

History Of ◽

Similar Affinity ◽

Leaved Forest

The Yunnan boast three broad-leaved forests, the semi-wet evergreen broad-leaved forest (SWEB) occurring in subtropical plateaus areas, the lower montane evergreen broad-leaved forest (LMEB) in tropical lower montane, and the upper montane evergreen broad-leaved forest (UMEB) in subtropical upper montane regions. Floristic composition and biogeography of these evergreen broad-leaved forests are studied and their diversification and divergence are revealed. I found similarities across the three forest types with species-rich families tending to have cosmopolitan distributions and families with less species exhibiting other distribution types. In biogeographical elements, the SWEB and the UMEB showed similar affinity in the proportion of tropical elements comprising total genera, specifically 45% and 44% respectively, and temperate elements totaling 46% and 48%, of all genera with northern temperate distribution comprising the highest ratio (18% in the SWEB and 20% in the UMEB ). LMEB tropical elements comprised 79% of the total genera, with tropical Asian distributed elements contributing the highest ratio (27%). While the three forest floras comprised of similar families, the same is not true at the genus and species levels. I suggest our results indicate divergence of the three forest floras, possibly from events in the geological history of Yunnan. From recent palaeobotanical studies, the diversification of floras of these evergreen broad-leaved forests in Yunnan occurred during the late Miocene with increased divergence with time in response not only to altitude changes and at the same time global cooling in Yunnan, but also the southeastward extrusion of Indochina geoblock influencing LMEB, and the Himalayan uplift affecting the floras of SWEB and UMEB.

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