Runaway Change in the Arctic? Extreme 2016 Temperatures

There is a philosophical issue on how to interpret new extreme events, dating back to the enlightenment, and this is true of whether new Arctic “surprises” are part of the existing population of events or not. Such a surprise was extensive record Arctic temperature extremes in January and February 2016 that continued into April. For January, the Arctic-wide averaged temperature anomaly was 2.0° C above the previous record of 3.0° C, with regional values in excess of 7° C. Extremes were caused by a major split in the tropospheric polar vortex with extensive warm air advection into the Arctic from western Russia and across Alaska. The Alaska track was related to a shift to a positive Pacific Decadal Oscillation (PDO) and warm NE Pacific surface temperatures after a cool North Pacific for most of the previous 15 years; this pattern is expected to continue for the next few years. 2016 Arctic extremes were thus “caused” by major Arctic connections with midlatitudes. Further, record summer sea ice loss minimum extents in 2007 and 2012 showed recovery in following years rather than a tipping point behavior. Greenland also shows extreme melting events in certain years from shifts in the atmospheric long wave circulation pattern phasing. Thus the answer to the question in the title appears to be no; continued increase in forcing from greenhouse gases is necessary for the continuation of surprises. Individual Arctic surprises also correspond to contributions from atmospheric circulation events. An open question is whether there is Arctic memory from surprises; Arctic change is happening faster than projected by climate models, which depend primarily on radiative forcing.