The Dominant Contribution of Southern Ocean Heat Uptake to Time‐Evolving Radiative Feedback in CESM

Abstract

AbstractIn most fully coupled climate models, the net radiative feedback magnitude decreases with time after abruptly quadrupling CO2. Hypotheses have been raised to explain the time dependence of radiative feedbacks, including the influence from surface warming pattern and ocean heat uptake (OHU) pattern. By using the Green's Function derived from pairs of simulations in the atmospheric model (CAM5) coupled with a slab‐ocean, with each simulation being forced by a localized surface heat flux anomaly, we evaluate the influences of regional OHU on transient surface warming pattern, accounting for the changes in radiative feedbacks. The attribution of the time‐evolving net radiative feedback highlights the remote impact from OHU over the Southern Ocean on tropical sea surface temperature. The time‐dependent weakening of OHU over the Southern Ocean gives rise to increasingly enhanced surface warming in southeastern Pacific, which leads to decreasing tropospheric stability and more positive cloud feedback decades after quadrupling CO2.