Influence of North Atlantic climate variability on glacier mass balance in Norway, Sweden and Svalbard

Climate variability can complicate efforts to interpret any long-term glacier mass-balance trends due to anthropogenic warming. Here we examine the impact of climate variability on the seasonal mass-balance records of 14 glaciers throughout Norway, Sweden and Svalbard using dynamical adjustment, a statistical method that removes orthogonal patterns of variability shared between each mass-balance record and sea-level pressure or sea-surface temperature predictor fields. For each glacier, the two leading predictor patterns explain 27-81 % of the winter mass-balance variability and 24-69% of the summer mass-balance variability. The spatial and temporal structure of these patterns indicates that accumulation variability for all of the glaciers is strongly related to the North Atlantic Oscillation (NAO), with the Atlantic Multidecadal Oscillation (AMO) also modulating accumulation variability for the northernmost glaciers. Given this result, predicting glacier change in the region may depend on NAO and AMO predictability. In the raw mass-balance records, the glaciers throughout southern Norway have significantly negative summer trends, whereas the glaciers located closer to the Arctic have negative winter trends. Removing the effects of climate variability suggests it can bias trends in mass-balance records that span a few decades, but its effects on most of the longer-term mass-balance trends are minimal.