Patterns of Ocean Heat Uptake and Time Varying Climate Sensitivity

Predicting the transient climate response or equilibrium climate sensitivity will help to adapt, mitigate, or possibly prevent
climate change. It is debated to which degree the horizontal and vertical pattern of thermal forcing influences
the equilibration of global surface temperature following a perturbation. For example, the aerosol distribution
or ocean heat uptake patterns can set the pace of both regional and global equilibration of a CO₂ induced
warming or cooling signal. Recent discussions suggest that high latitude ocean heat uptake or release is more
efficient in cooling or warming the global atmosphere than low latitude heat uptake or release. This implies that knowledge of the evolution of heat uptake
patterns is a necessary condition to predict global climate sensitivity.
So far these effects have been mostly studied in equilibrium idealized aqua planet simulations without
seasons or sea ice. We analyze fully coupled GCM and intermediate complexity model simulations with
realistic continents, sea ice distribution, and seasonality. We show how local ocean heat content equilibrates
on time scales of decades to millennia and then force a slab ocean model with characteristic deep ocean
heat uptake patterns for different time slices. The aim is to imitate several stages in the equilibration
process, presenting low versus high latitude northern or southern hemispheric ocean heat uptake. We discuss which
atmospheric feedbacks enhance or dampen the ocean heat uptake signal depending on the location. We
finally show to which degree and where local heat uptake can impact global climate sensitivity.