Arctic glacier snowline altitudes rise 150 m over the last 4 decades

Over the last 4 decades, Arctic glacier SLAs have risen an average of similar to 152 m (3.9 +/- 0.4 m yr(-1); R2=0.74, p<0.001), with a corresponding summer (June, July, August) temperature shift of +1.2 degrees C at the glacier locations. This equates to a 127 +/- 5 m shift per 1 degrees C of summer warming. However, we note that the effect of glacier surface thinning could bias our estimates of SLA rise by up to similar to 1 m yr(-1), a significant fraction (similar to 25 %) of the overall rate of change, and thus should be interpreted as a maximum constraint.

Along with warming, we observe an overall decrease in snowfall, an increase in rainfall, and a decrease in the total number of days in which the mean daily temperature is less than or equal to 0 degrees C. Glacier SLA is most strongly correlated with the number of freezing days, emphasizing the dual effect of multi-decadal trends in mean annual temperature on both ablation (increasing melt) and accumulation processes (reducing the number of days in which snow can fall).

Although we find evidence for a negative morpho-topographic feedback that occurs as glaciers retreat to higher elevations, we show that more than 50 % of the glaciers studied here could be entirely below the late-summer SLA by 2100, assuming the pace of global warming and the mean rate of SLA rise are maintained.