Understanding Intermodel Diversity of CMIP5 Climate Models in Simulating East Asian Marginal Sea Surface Temperature in the Near Future (2020–2049)

Abstract

Using 14 Coupled Model Intercomparison Projections Phase 5 (CMIP5) climate models, we examined the intermodel diversity when simulating East Asian Marginal Seas (EAMSs) sea surface temperature (SST) in the near future period (2020–2049) under four different Representative Concentration Pathway runs. We classified two groups for the CMIP5 climate models: for models that simulate SSTs in the EAMS that are higher (H_EAMS) and lower (L_EAMS) than the ensemble mean, respectively. Results show that compared to L_EAMS, H_EAMS tends to simulate weaker westerlies in the western‐to‐central North Pacific, together with a weaker Aleutian Low intensity, which causes higher EAMS SSTs through a reduction in latent heat flux. Furthermore, H_EAMS is characterized by cooler SST, less precipitation, and stronger trade winds in the central‐to‐eastern tropical Pacific than in L_EAMS. We argued that the intermodel diversity of simulated tropical Pacific SST is associated with the diversity of EAMS SST, which is related to atmospheric teleconnections from the tropics to the western‐to‐central North Pacific. It is also found that the bifurcation latitude of the North Equatorial Current is lower in H_EAMS than in L_EAMS, which is associated with the difference of tropical Pacific mean state between H_EAMS and L_EAMS. A lower bifurcation latitude transports more warm water into the EAMS, resulting in warmer SSTs in the H_EAMS than in the L_EAMS. These results show the importance of correctly simulating the tropical Pacific mean state to reduce the uncertainty in EAMS SST during the near‐future period.

Simulated and projected SST of Asian marginal seas based on CMIP6 models

“…In this study, larger SST bias and inter-model diversity are found in the East/Japan Sea and the East China Seas. In the previous studies, it has been pointed out that the dynamical processes causing intermodel diversity in simulating East AMS SST during the near-future period (2020 -2049) may be not limited to local variables, but linked to Pacific Ocean basin-scale processes, and the inter-model diversity in simulating East AMS SST is influenced by both atmospheric and oceanic processes associated with the North Equatorial Current bifurcation latitude (Yi and Yeh, 2019). These findings suggest that in order to reduce AMS SST uncertainties from CMIP6 climate models, it is critical to correctly simulate the tropical Pacific mean state simulations.…”

“…On the contrary, the amplitudes of seasonal variations are overestimated along the north coast of the Sea of Okhotsk, the western Arabian Sea, the eastern Bay of Bengal, and the Philippine Sea, with the largest positive biases of approximately 2°C occurring in the western Arabian Sea and the eastern Bay of Bengal (Figure 2I). Yi and Yeh (2019) pointed out that the East AMS SST bias is related to atmospheric teleconnections from the tropical to the western-to-central North Pacific. The East AMS SST bias is also associated with the bifurcation latitude of the North Equatorial Current, a low bifurcation latitude transports more warm water into the East AMS (Yi and Yeh, 2019).…”

“…Yi and Yeh (2019) pointed out that the East AMS SST bias is related to atmospheric teleconnections from the tropical to the western-to-central North Pacific. The East AMS SST bias is also associated with the bifurcation latitude of the North Equatorial Current, a low bifurcation latitude transports more warm water into the East AMS (Yi and Yeh, 2019). In the Arabian Sea, a clear relationship exists between cold SST bias and weak monsoon rainfall in CMIP5 models during winter (Levine and Turner, 2012;Levine et al, 2013).…”

“…For example, the warming trends of boreal winter SST in the ECS and the Taiwan Strait exceed 2.7°C per hundred years (Liu and Zhang, 2013), about two times larger than the global mean SST trend (Sasaki and Umeda, 2021). The dynamics could attribute to increasing oceanic heat advection, acceleration of the Kuroshio, local atmospheric forcing, and a weakening East Asian monsoon (Yeh and Kim, 2010;Seo et al, 2014;Cai et al, 2017;Yi and Yeh, 2019;Sasaki and Umeda, 2021;Wang and Wu, 2022).…”

“…The Asian Marginal Seas (AMS), which extend from the nearpolar to the near-equatorial regions and span most of the climatic zones of the Earth, affecting the largest amount of population in the world, and are probably to be the most heavily impacted by anthropogenic activities (Barale, 2018;Nam et al, 2022). The AMS SST plays an important role in modulating the Asian monsoon system (Li et al, 2010;Yi and Yeh, 2019), thereby impacting on the socioeconomic conditions of the Asian countries with large populations located around the coast of the AMS. In addition, the AMS are also known as one of the major distribution regions of coral reefs, mangroves, and fishery (Spalding et al, 2001;Giri et al, 2011;Veron et al, 2015;Bai et al, 2018).…”