Present and future changes in winter climate indices relevant for access disruptions in Troms, northern Norway Anita Verpe Dyrrdal1, Ketil Isaksen1, Jens Kr. Steen Jacobsen2, Irene Brox Nilsen3 1Department of Research and Development, Norwegian Meteorological Institute, Oslo, 0313, Norway 5 2Institute of Transport Economics, Oslo, 0349, Norway 3Norwegian Water Resources and Energy Directorate, Oslo, 0301, Norway Correspondence to: Anita Verpe Dyrrdal (
[email protected]) Abstract. A number of seaside communities in Troms in northern Norway are vulnerable to sudden weather induced access 10 disruptions due to frequent high impact weather and dependency on one or few roads exposed to avalanches, wind, and challenging road conditions. In this paper we study changes in selected indices describing winter weather known to potentially cause such access disruptions in Troms. A gridded observation-based dataset is used to analyse changes in present climate (1958–2017), while an ensemble of ten EURO-CORDEX climate model simulations are used to assess expected future changes in the same indices, towards the end of the twenty-first century. We focus on climate indices 15 associated with snow avalanches (such as maximum snow amount, snowfall intensity and frequency, and strong snow drift) and slushflows where rainfall during winter is highly relevant. All climate indices are also associated with access disruptions in general, including freeze-thaw cycles described as zero-crossings (temperature crossing 0 °C) that may lead to slippery road conditions. Our results show that there are large climate gradients in Troms and also in detected changes. In our two focus areas, Senjahopen/Mefjordvær in Berg municipality and Jøvik/Olderbakken in Tromsø municipality, we find that the 20 studied snow indices have become more frequent in present climate, while they expect to become less frequent in near and far future, particularly in low elevations where snow cover during winter might become a rarity by 2100.