CMIP5 projections of Arctic amplification, of the North American/North Atlantic circulation, and of their relationship

Abstract:

Recent studies have hypothesized that enhanced Arctic warming (termed
Arctic amplification) will cause changes in midlatitude weather over
the 21st Century. Here we exploit the recently completed Phase 5 of
the Coupled Model Intercomparison Project (CMIP5), and examine 27
state-of-the-art climate models to determine if their projected
changes in the midlatitude circulation are consistent with the
hypothesized influence of Arctic amplification over North America and
the North Atlantic.

We find that although every model, and in all four seasons, exhibits
Arctic amplification by 2100 under RCP8.5, the projected midlatitude
changes of the circulation are either opposite in sign to those
hypothesized, or too widely spread among the models to discern any
robust change. Interestingly enough, in certain seasons and for a few
of the circulation metrics we have examined, we do find correlations
between the model spread in Arctic amplification and the model spread
in the projected circulation changes, in some cases opposite to the
ones previously hypothesized, but work is needed to determine whether
a causal link actually exists.

Irrespective of any potential link, the CMIP5 models we have analyzed
clearly indicate that Arctic amplification will NOT be the dominant
driver of the projected changes in the circulation in the context of
the hypothesized mechanism over the 21st Century.