Does Polar Warming Asymmetry Exist in Bathy‐Planet Experiments?

Abstract Ocean bathymetry and continental geometry shape ocean circulation, but whether these geographic constraints can sustain polar warming asymmetry in a fully coupled climate system remains unclear. Here we construct a fully coupled “bathy‐planet” configuration (BATHY), in which continental topography is removed and most land surfaces are replaced by a 10‐m‐deep ocean with active ocean dynamics, while realistic ocean bathymetry and continental geometry are retained. Under abrupt 4 × CO 2 forcing, BATHY exhibits stronger Arctic than Antarctic warming. Feedback decomposition indicates that this asymmetry mainly reflects enhanced Arctic warming from surface‐albedo feedback and reduced Antarctic warming due to Southern Ocean heat storage and transport changes. Moisture‐related processes further modulate the asymmetry. Normalization by the surface‐albedo contribution largely removes the raw warming contrast. These results show that polar warming asymmetry persists even when continental topography is removed and most land surfaces are replaced by shallow ocean.