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

61

Chapter 4 · Physical and socio-economic environment

challenge to communities and have a strong effect on sectors such as tourism, fishing, offshore, and shipping. These phenomena are associated with strong winds and high waves, and recent reports suggest a connection between cyclones (i.e. storms) and ROS events (Hansen et al., 2014; Roshydromet, 2014). Heavy snowfall can result in snow-induced forest damage, and in the period 1961–2000 the maximum number of heavy snow-load events occurred in 1994 in northern Finland (Rasmus et al., 2015). Stratospheric temperatures may influence ground conditions through indirect effects on circulation patterns (such as the NAO/AO,jet streams,and storm tracks) or volcanic eruptions (Baldwin andDunkerton,2001;Thompson et al.,2002; Bhend, 2015; Kidston et al, 2015). Ozone concentrations in the stratosphere affect the amount of solar radiation reaching the Earth’s surface, and so control the intensity of the short-wave ultraviolet radiation that may harm living organisms and affect human health. Manney et al. (2011) reported unprecedented chemical ozone destruction over the Arctic in early 2011 that was comparable to that in the ‘Antarctic ozone hole’. 4.2.1 Warming Annual average temperature in the Barents area increased by 1–2°C over the period 1954–2003, with warming strongest in winter (Callaghan et al., 2005).The observed rate of increase in NyÅlesund (Svalbard) for the period 1994–2013 was 1.3°C per decade (Maturilli et al., 2014), again with the increase greatest in winter (3°C per decade). A new set of temperature and precipitation projections has been generated for the Barents area by empirical-statistical downscaling of results from the CMIP5 ensembles of General Circulation Models (GCMs) driven by the RCP2.6, RCP4.5 and RCP8.5 emission scenarios (Benestad et. al., 2016). Large ensembles are likely to capture the effect of natural variations (Deser et al.,2012) and by comparing the downscaled results and observations it is clear that the range in model results is similar to that for the observed interannual variability (Figure 4.1).The downscaleddata indicate that the warmest (95th percentile) winter temperatures over the land-area surrounding the Barents Sea are likely to

such as the SWIPAassessment (AMAP,2012),theArctic Climate Impact Assessment (ACIA, 2004, 2005), the fifth assessment of the Intergovernmental Panel on Climate Change (IPCC, 2014), the NordAdapt project (The ResearchCouncil of Norway,2008), and a recent assessment of climate change for the Baltic Sea Basin (The BACCII Author Team, 2015) with some results that are relevant to theArctic.The projections and scenarios involve foresight based on empirical information, known behavior, and interaction between drivers and impacts,but exclude unknowns and are limited by incomplete knowledge. For example, there are real risks of abrupt change or the crossing of tipping points, but it is extremely challenging (if not impossible) to identify the exact threshold for their trigger action. Relevant tipping points include cessation of the World Ocean Thermohaline Circulation, methane release, disintegration of the Greenland ice sheet and irreversible loss of biodiversity (ACIA 2004; Arctic Council, 2013). The future may also bring surprises because there is still much to be understood about drivers and feedbacks, and there may be many unknown unknowns (see Appendix 4.1). 4.2 Changes in the atmosphere TheArctic regionwas long expected to warmat a faster rate than global mean temperature due to ‘polar amplification’ (Manabe and Stouffer, 1980).This has now been observed (Kattsov et al., 2011; Rutgersson et al., 2015) and is expected to continue (Kirtman et al., 2013; Collins et al., 2013). Several conditions associated with global warming are likely to have important consequences for the Arctic environment and Arctic societies (see Appendix 4.2). The rise in temperature is associated with ice and snow melt (Callaghan et al., 2011; Liston and Hiemstra, 2011; Roshydromet, 2014, 2016) as well as changes in the vegetation. Changes in ice, snow, and vegetation will in turn influence albedo and surface fluxes, while melting land ice contributes to rising sea level and changes in ocean salinity that may drive changes in the global thermohaline circulation.Higher temperatures also affect permafrost (Isaksen et al., 2007a,b; Etzelmüller et al., 2011; Koven et al., 2013; Roshydromet, 2014), causing an increase in active layer depth,permafrost degradation and a northward shift in the southern limit of the permafrost. Changes in permafrost have consequences for infrastructure and the built environment. Changes in temperature also affect the relative proportions of precipitation falling as snow and rain (Hansen et al., 2014; Roshydromet, 2014).There have been more frequent occurrences of rain-on-snow (ROS) and winter warming events (Vikhamar-Schuler et al.,2016),with an average increase of 0.2 to 2.5 events per winter per 1°C temperature rise in the Barents area according to Rasmus et al. (2015). Higher temperatures also increase the moisture-holding capacity of the atmosphere, and Rinke et al. (2011) projected significant changes in temperature, precipitation and snow indices over the 21st century. The observed rise in precipitable water over recent decades has been greatest in summer and early autumn and over the northern NorthAtlantic, including the Norwegian and Barents seas (Serreze et al., 2012).Added to this, a declining sea-ice cover favors increased evaporation from the Arctic seas and in turn influences the weather (Vihma,2014).Other aspects, such as changes in storm statistics and frontal activity, present a

Air temperature, °C

10

5

0

-5

-10

-15

-20

2100

1900

1950

2000

2050

Observation

RCP2.6

RCP4.5

RCP8.5

Figure 4.1 Comparison of observed temperature and computed winter- mean temperature for the period 1900–2100 at Svalbard airport for the RCP2.6, RCP4.5, and RCP8.5 emission scenarios (Benestad et al., 2016).