Synchronous Strengthening of the Indian and East Asian Monsoons in Response to Global Warming Since the Last Deglaciation

Wenying Jiang (1) , Suzanne Leroy (2) , Shiling Yang (1, 3) , Enlou Zhang (4) , Luo Wang (1) , Xiaoxiao Yang (1) , Patrick Rioual (1, 5)

1 IGG - Institute of Geology and Geophysics [Beijing]
2 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
3 UCAS - University of Chinese Academy of Sciences [Beijing]
4 Niglas - Nanjing Institute of Geography and Limnology
5 CAS Center for Excellence in Life and Paleoenvironment

The responses of the Indian and East Asian summer monsoons (ISM and EASM) to warming since the last deglaciation are controversial. Pollen results from a subalpine lake in the ISM area show that the Tsuga dumosa forest zone migrated at least 650 m upward during 18.6-7.1 kyr BP, indicating a gradual rise in mean annual temperature exceeding 3.9°C. In response, grasses and deciduous and evergreen broad-leaved trees successively colonized the mountainous environment. By contrast, the area around a lake in the EASM area was gradually occupied by temperate deciduous trees. In both areas, the maximum monsoonal precipitation occurred during 7.1-6.4 kyr BP, coinciding with peak Holocene warmth, but lagging the peak in Northern Hemisphere summer insolation by 3.9-4.6 kyr, due to delayed ice melting in northern high latitudes. Our results indicate the synchronous strengthening of the ISM and EASM in response to warming-induced northward shifts in the Intertropical Convergence Zone. Plain Language Summary The responses of the Indian summer monsoon (ISM) and East Asian summer monsoon to past global warming provide valuable insights into future climate scenarios. A paleovegetation reconstruction from the ISM area shows a gradual warming of over 3.9°C in mean annual temperature from 18.6 to 7.1 kyr BP. The ISM and East Asian summer monsoon strengthened synchronously in response to warming-induced shifts in the Intertropical Convergence Zone and reached their peak at 7.1-6.4 kyr BP, lagging the summer insolation maximum by 3.9-4.6 kyr, due to delayed ice melting in northern high latitudes. As future warming continues, the loss of habitat for Tsuga dumosa and other alpine species will accelerate in the ISM area, and the abundance of deciduous trees will increase in northern China.

Domaines: Milieux et Changements globaux; Climatologie

Wenying Jiang, Suzanne Leroy, Shiling Yang, Enlou Zhang, Luo Wang, et al.. Synchronous Strengthening of the Indian and East Asian Monsoons in Response to Global Warming Since the Last Deglaciation. Geophysical Research Letters, 2019, 46 (7), pp.3944-3952. ⟨10.1029/2019GL082084⟩. ⟨hal-02546062⟩