Adaptation Actions for a Changing Arctic: Perspectives from the Barents Area

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Chapter 4 · Physical and socio-economic environment

In Finland and Russia, there have been reports of greater SD but shorter SCD, and SCD is more sensitive to climate change. Recent updates (Brown and Schuler, 2017) show significant trends for the period 1966–2014 inmaximum annual SD in two Russian Arctic regions: the Atlantic Arctic (1.4% per decade) and eastern Siberia (2.4% per decade).This tendency contrasts with that observed in regions with warmer winter climates (e.g. Scandinavia and the Baltic Sea Basin), where the sign and magnitude of the trends in SWE and maximum SD can vary significantly with elevation and distance to the coast. There are three possible explanations for the recent increase in SD across most of northern Eurasia. First, loss of Arctic sea ice at the start of the cold season has enabled additional water vapor influx into the dry Arctic atmosphere, leading to greater snowfall further south. Second, changes in atmospheric conditions through more intensive cyclonic circulation and more frequent storms have contributed to increased snowfall (Callaghan et al., 2011). Finally, increased precipitation (see Section 4.2.2) Maximum SD is projected to increase over many areas by 2050, however, the snow season is expected to continue shortening due to the earlier onset of spring melt (Brown and Schuler, 2017). As part of the ENSEMBLES project, Räisänen and Eklund (2012) used regional climate model simulations based on the SRES A1B scenario to project future changes in SWE in northern Europe. They found a general decline in snow amount over the 21st century, but high regional and interannual variability. Individual snow-rich winters may still occur in future decades despite a long-term decline in mean SWE. Climate models project greater changes in future SCD than SWE in the Arctic (Brown and Schuler, 2017). Snow cover in the warmer coastal regions of the Arctic (such as in Alaska and Scandinavia) shows the strongest sensitivities to the warming projected. Only northern Siberia and the Canadian Arctic are projected to see an increase in maximum SD. This contrasting pattern of projected change in maximum SWE is a consequence of the impact of non-linear interactions between rising temperature and increasing precipitation, on snowfall, the snow accumulation period and winter melt events (Räisänen, 2008). 4.4.1.5 Snow quality Changes in winter climate and especially the frequency and intensity of winter warming events (with or without rain) affect snow properties such as albedo, temperature, density, snow grain size distribution, and ice layers.An observational study by Johansson et al. (2011) of 49 years of snow profile stratigraphy data from Abisko (Sweden), showed an increase in very hard snow layers between 1961 and 2009, with harder snow in early winter and more moist snow during spring. Towards the end of the observation period the number of occasions with very hard snow layers in the snow-pack had more than doubled. Temperature and precipitation both increased over this period, with the increase in air temperature particularly strong at the start and end of the snow season.Warming events followed by low temperatures increase snow-pack density and can generate ice layers in the snow. These ice layers can impede access to forage for caribou,musk-ox and reindeer (Forchhammer et al.,

and Schuler, 2017).Across much of the northern hemisphere, the date of melt onset advanced by about 1–2 weeks over the period 1979–2012 (Mioduszewski et al., 2014).The strongest trends in SCD occurred in northern and western Eurasia. Arctic coastal and island areas experienced a statistically significant decline in SCD over the period 1978–2007 (Callaghan et al., 2011). There was a statistically significant decline in SCD of about 3 days per decade in Fennoscandia over the period 1951–2007. For the period 1978–2007, there was a statistically significant decline in SCD of 7.3 days per decade over the Fennoscandian sector and 6.3 days per decade over the Barents Sea sector. Rasmus et al. (2014a,b) found the snow season had shortened over the past 30 to 50 years at several observation sites in the reindeer management area of Finnish Lapland. Between 1979 and 2007, melt onset near Sodankylä in northern Finland advanced by 3.4 days per decade, and over northern Fennoscandia, SCD was projected to decrease by 10–15 days under 1°C warming, 15–25 days under 2°C warming, 20–35 days under 3°C warming, and 25–45 days under 4°C warming (Lehtonen et al., 2013). In the Atlantic areas of Russia, Bulygina et al. (2011) found the number of days with snow covering more than 50% of the area surrounding a meteorological station decreased by 1.4% per decade between 1966 and 2010. Callaghan et al. (2011) found SCD over northern Europe and Siberia has decreased since 1980. The decline in SCD is projected to be greatest over northern Scandinavia.SCD in 2050 is projected to be 30-40% shorter than in 2011 (Brown and Schuler, 2017), and the expected fall in the annual number of snow cover days in northern Fennoscandia is projected to be greater in coastal regions than mountainous areas (Lehtonen et al., 2013).The main reason for the decline in SCD appears to be earlier melt onset in spring and later freeze- up in autumn.When compared to the mean length of the snow season for 1981–2010, the decrease is expected to vary from 10 to 40 days with a rise in temperature of 1–4°C. Annual SCD is projected to decrease by 10–20% over most of the Arctic by 2055 under the RCP8.5 emissions scenario (Brown and Schuler, 2017) but withmuch larger decreases (>30%) over the European sector andwesternAlaska.However,themagnitude and temporal evolution of the projected changes in SCD averaged over the Arctic are strongly dependent on the emission scenario used as the basis for the projected changes in climate. 4.4.1.4 Snow depth and snow water equivalence Although SCD has broadly decreased across the Arctic, snow depth (SD) and snow-water equivalent (SWE) (mean and maximum values) have shown wide regional variations with both increasing and decreasing trends observed.According to Rasmus et al. (2015), there has been a long-term increase in SD and SCD over most of northern Eurasia. Although maximum SD showed little change in northern Sweden over the period 1905–2003, there has been an increase in mean winter SD of about 2 cm (5%) per decade since 1913 and 10% since 1930–1940 (Rasmus et al., 2015).The duration and maximum thickness of the basal ice layer has decreased in the European part of Russia since 1966. SD over Eurasia increased over the period 1966–2010 over Eurasia (Bulygina et al., 2011).