An interdecadal extension of the Indo-Pacific warm pool and its strengthened influence on the South China Sea summer monsoon since the late 1980s

Abstract

In this study, the interdecadal change in the size of the Indo-Pacific warm pool (IPWP) and its connection with the intensity of the South China Sea summer monsoon (SCSSM) in May are investigated. The results show that the size of the IPWP experienced a marked interdecadal extension in the late 1980s, and its impacts on the SCSSM have also strengthened. Further analyses indicate that interdecadal changes in the connection between the IPWP and SCSSM variations are related to the changes in the atmospheric circulation anomalies over the tropical western Pacific due to the size of the IPWP. During 1951-1986, the IPWP was smaller than the climatologic size, which led to suppressed convection over the tropical western Pacific and easterly anomalies north of the equator. The Philippines and South China Sea (SCS) region was controlled by anomalous anticyclonic circulation, which was not conducive to the formation and development of the SCSSM. In contrast, during 1987-2018, the IPWP expanded significantly eastward. As a response to the IPWP size extension, convective activities were enhanced over the tropical western Pacific. Anomalous cyclonic circulation was located over the Philippines and SCS regions, which favored the enhancement of the SCSSM through wide westerly flow in the Bay of Bengal and tropical western Pacific. Moreover, it is shown that the interdecadally enhanced intraseasonal oscillations (ISOs) over the tropical western Pacific in the late 1980s also favored reinforcement of the SCSSM intensity.

Weakening seasonality of Indo-Pacific warm pool size in a warming world since 1950

“…In addition to its characteristics, the impacts of the IPWP on climate also exhibit obvious seasonality. For example, the variability of winter IPWP is a major factor controlling the Madden-Julian Oscillation (MJO; Roxy et al 2019); that of spring IPWP affects the summer monsoon in East Asia and the South China Sea (Yin et al 2020) and the precipitation in Africa through its affect on Walker circulation (Williams and Funk 2011); that of summer IPWP is crucial to the genesis and development of tropical cyclones in the Indo-Pacific region (Yang and Zheng 2018); and that of autumn IPWP could affect precipitation in western China (Wei et al 2018), etc.…”

“…Climate model simulations showed that 85% of the IPWP's expansion in the past decades is a result of human influence (Bai et al 2022). The influence of the recent human-caused expansion of the IPWP on climate systems has been widely discussed, for example Hadley circulation, Walker circulation (Brierley et al 2009, Williams and Funk 2011, tropical cyclones (Webster et al 2006, Benestad 2009, East Asian summer monsoon (Kim et al 2020, Yin et al 2020, Jian et al 2022, MJO (Roxy et al 2019, Dasgupta et al 2020, the El Niño-Southern Oscillation (ENSO) (Sun 2003) and precipitation over different regions (Zhou 2014). Besides, expansion of the IPWP will also have important impacts on its ecological environment, such as changing the species composition and improving the productivity of mangroves in Indonesia (Field 1995, Shearman et al 2013, Patrick et al 2016, changing the life cycle of planktic organisms in the IPWP (Patrick 2016), promoting the growth rate and biomass accumulation of phytoplankton (Winder and Sommer 2012) and altering the patterns and predictors of marine biodiversity (Tittensor et al 2010).…”

Relationship between the hadley circulation and tropical SST meridional structures under different thermal conditions in the indo-pacific warm pool

“…In addition, researchers found a significant 10-year period oscillation in the IPWP volume. The SSTs in the IPWP have a decadal mutation around 1976-1986, showing a negative anomalous feature before 1976 and a positive one after 1986 (Yin et al, 2020). However, a suppressed circulation over the tropic PO would occur when the SST or the extent size of IPWP is significantly weaker than the climatology.…”

Impacts of the Western Pacific and Indian Ocean Warm Pools on Wildfires in Yunnan, Southwest China: Spatial Patterns With Interannual and Intraannual Variations

“…The Indo‐Pacific warm pool is the largest continuous warm sea surface on earth, with a strong effect on both tropical and extratropical climate (De Garidel‐Thoron et al., 2005; Roxy et al., 2019; Weller et al., 2016; Yan et al., 1992). Convincingly, as one of the energetic components of the earth‐surface system, Asian monsoon is also intensely impacted by the conditions of the Indo‐Pacific warm pool (Lu & Lu, 2015; Shin et al., 2011; Xie et al., 2009; Yin et al., 2020a). Several studies even suggested that the warm pools rather than the land‐sea thermal contrast, are the primary forcing agents of monsoons (Chao & Chen, 2001; Shields & Kiehl, 2018).…”