On the timescales of the response of the Brewer‐Dobson Circulation to an abrupt quadrupling of CO2

This study aims to disentangle these two contributions in the Whole Atmosphere Community Climate Model (WACCM) by analyzing the timescales of the tropical upwelling response to an abrupt quadrupling of CO 2 .

Transient atmosphere‐ocean climate model simulations of 100 years under 4xCO 2 conditions are compared to preindustrial control simulations and to simulations with an atmosphere‐only version of WACCM that uses preindustrial SSTs. We find that most of the response in both shallow and deep branches of the BDC occurs on fast timescales (first 2‐3 decades). In the shallow branch of the BDC, the response is mainly driven by changes in SSTs in the well‐mixed shallow ocean, which cause tropospheric warming and an intensification and upward displacement of the subtropical jets, and alter wave forcing in their vicinity.