Abstract:

The Arctic exhibits both the largest sensitivity and the largest uncertainty in projected warming of any region on Earth. However, disentangling the drivers of polar climate change remains a challenge. This talk will use comprehensive and idealized models to isolate the mechanisms of Arctic warming, its seasonality, and its uncertainty. An idealized sea-ice model will show that seasonality in Arctic warming is fundamentally driven by the increasing thermal inertia of the surface layer as sea ice melts and transitions to open ocean. Experiments that impose the model uncertainty in the Atlantic Meridional Overturning Circulation will demonstrate that this uncertainty in ocean circulation can reproduce nearly half the total uncertainty in projections of Arctic warming. Lastly, experiments that disable individual climate feedbacks to capture their full effects will highlight a key role for the water vapor feedback in amplifying Arctic warming. These mechanism-denial approaches challenge our diagnostic understanding of the drivers of polar warming, offering opportunities to improve polar climate projections.