Cohen, J., J.A. Screen, J.C. Furtado, M. Barlow, D. Whittleston, D. Coumou, J. Francis, K. Dethloff, D. Entekhabi, J. Overland, and J. Jones (2014): Recent Arctic amplification and extreme mid-latitude weather. Nature Geosci., 7(9), doi: 10.1038/ngeo2234, 627–637.
Improved understanding of new potential Arctic-lower latitude weather linkages and implications for weather and climate predictions
The role of the Arctic in the global climate system is based on multiple processes unique to the Arctic, driven by modest global warming. Arctic temperatures continue to increase at least 3 times the rate of mid-latitude temperatures. Multiple feedbacks, such as clouds, loss of sea ice and snow cover, heat storage in the ocean, and atmospheric dynamics are a hypothesized cause for this phenomenon known as Arctic amplification. For example, more sunlight is captured in newly sea-ice free ocean areas.
It is reasonable to suspect that Arctic change, which can produce the largest temperature anomalies on the planet and demonstrates recent extremes in the waviness of the polar vortex, could be linked to mid-latitude weather. Some within the meteorological community remain skeptical of this linkage, however, in the sense that it is “not proven.” Natural variability in chaotic atmospheric flow remains the main meteorological process, and it is difficult to determine whether Arctic forcing of a north-south linkage is emerging during the recent period of Arctic change. Nonetheless, such a hypothesis is worthy of investigation, as continued Arctic changes may be the principal opportunity for improved extended forecasts at mid-latitudes. Work on this topic provides a major challenge for NOAA and the international science community.
Large-scale weather patterns, such as jet stream meanders (polar vortex), blockings (slowdown of the jet stream), shift in the Arctic Oscillation climate pattern, teleconnections, shifts in the number of planetary waves, etc., are prominent features characterizing the daily-to-decadal variability of the subarctic atmosphere. These patterns may have recently demonstrated systematic variations in intensity, frequency, and locations, depending on the measures used. These shifts are a potential mechanism for Arctic mid-latitude weather linkages, but the degree to which they are driven in part due to Arctic changes remains largely uncertain.