Aerosol emissions influence the evolution of North Pacific gyre circulation

Chen Xing

UC Santa Barbara

Tuesday, Sep 13, 2022, 2:00 pm


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North Pacific climate variability profoundly impacts local and global climate and ecosystems, but its response to external forcing is still under debate. Anthropogenic aerosol emissions are particularly poorly understood, but have the potential to strongly affect Pacific climate variability on decadal timescales. Here we use full and single-forcing large ensembles run with the Community Earth System Model (CESM) versions 1 and 2 to assess how Pacific ocean variability has been affected by historical aerosol emissions. We detected significant multi-decadal North Pacific responses to anthropogenic aerosol emissions in both CESM1 & 2 in the past 100 years. Aerosol emissions drive mean state changes over the North Pacific, with decreased shortwave radiation on the surface associated with cooling and weakened Aleutian low sea level pressure anomalies. Through Ekman pumping, surface easterly wind stress anomalies reduce mass transport to the KOE region followed by a decrease in sea surface height, and the results are verified by the ocean Rossby wave model. We also compare KOE responses in two different versions of CESM, and point out the impact of model aerosol forcing changes on climate responses. Our findings highlight the importance of anthropogenic aerosol forcing on Pacific climate variability, as well as the utility of large ensemble single forcing simulations in isolating forced signals.

Speaker Bio: Chen is a PhD student, who joined the Bren School of Environmental Science and Management at University of California Santa Barbara (UCSB) in Fall 2020. She received a Bachelor degree in Atmospheric Sciences from Nanjing University of Information Science & Technology (NUIST) in Nanjing in 2017. She was previously a graduate student at the NUIST, where she studied the influence of volcanic aerosols on the El NiƱo/Southern Oscillation. At UCSB, she is beginning investigations into human-driven greenhouse gas and aerosol emissions on Pacific Decadal Variability in large ensemble models and other CMIP models.

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