Climate dynamics

Abstract:

Climate models predict a weak poleward shift of the jets in response to continuing climate change. Here we revisit observed jet trends using 40 years of satellite-era reanalysis products and find evidence that general poleward shifts are emerging. The significance of these trends is often low and varies between datasets, but the similarity across different seasons and hemispheres is notable. While much recent work has focused on the jet response to amplified Arctic warming, the observed trends are more consistent with the known sensitivity of the circulation to tropical warming. The circulation trends are within the range of historical model simulations but are relatively large compared to the models when the accompanying trends in upper tropospheric temperature gradients are considered. The balance between tropical warming and jet shifts should therefore be closely monitored in the near future. We hypothesise that the sensitivity of the circulation to tropical heating may be one factor affecting this balance.

Abstract:

Previous studies have found inconsistent responses of the North Atlantic jet to Arctic sea-ice loss. The response of wintertime atmospheric circulation and surface climate over the North Atlantic-European region to future Arctic sea-ice loss under 2°C global warming is analyzed, using model output from the Polar Amplification Model Intercomparison Project. The models agree that the North Atlantic jet shifts slightly southward in response to sea-ice loss, but they disagree on the sign of the jet speed response. The jet response induces a dipole anomaly of precipitation and storm track activity over the North Atlantic-European region. The changes in jet latitude and speed induce distinct regional surface climate responses, and together they strongly shape the North Atlantic-European response to future Arctic sea-ice loss. Constraining the North Atlantic jet response is important for reducing uncertainty in the North Atlantic-European precipitation response to future Arctic sea-ice loss.