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

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

rather than snow, but little change in total precipitation. They connected the loss of snow on ice to a decrease in surface albedo over theArctic Ocean,which they found to be comparable to the reduction in albedo associated with the decline in sea ice. The decline in summer snowfall may also explain the thinning of sea ice over recent decades and provides support for the existence of an amplifying feedback associated with warming-induced reductions in summer snowfall. Local climatic conditions affect precipitation phase, leading to different trends for snowfall (and rain) across the Arctic. Regions with warmer winter climates, such as Scandinavia and the Baltic Sea Basin, have seen declining snowfall trends (Irannezhad et al., 2016), whereas increasing trends have been reported for regions with colder winter climates,such as Canada and Siberia (Kononova, 2012; Vincent et al., 2015). Räisänen (2016) used data from 12 RCMs (SRES A1B scenario) from the ENSEMBLES project to project changes in snowfall in northern Europe through the 21st century. Results indicate a decrease in total winter snowfall across almost all of northern Europe by 2069–2099.In contrast,snowfall in themiddle of winter is projected to increase in the coldest areas: northern Finland, northern Sweden, northernNorway and the Kola Peninsula. But even in these areas,results indicate a general decline in total annual snowfall.This is due to a decline in the number of snowfall days. By 2100, the number of snowfall days may be 10–20% lower in northern Fennoscandia, and 20–50% lower in coastal areas. However, there may be a slight increase (0–10%) in average snowfall intensity during snowfall days. Rutgersson et al. (2015) associated higher snowfall in the Arctic with excess moisture due to warm conditions in the preceding summer and autumn. 4.4.1.2 Snow cover extent Historical and projected changes in Arctic snow-cover extent (SCE) are reported in the SWIPA update (Brown and Schuler et al., 2017). Changes in spatial, temporal and seasonal SCE reflect changes in drivers such as Arctic warming, Arctic moistening andArctic greening, and interaction between these drivers and feedback mechanisms. Since 1980 there have been widespread decreases in Eurasian SCE, especially over northern Scandinavia. The ACIA assessment reported a 10% decline in SCE over 30 years, with increasingly shorter snow seasons (ACIA, 2004) associated with increased rates of freezing and thawing. The reinforcing snow albedo feedback has played a key role in the poleward retreat of spring and early summer SCE, and the most pronounced decline in SCE has occurred at high latitudes (60°–70°N) where the potential impacts of snow albedo feedback are greatest. The decline in SCE accelerated between 2007 and 2014, especially in Eurasia where the trend over 1971–2014 was amplified compared 1972–2006. This amplification was mainly due to the stronger decline in SCE over 1971–2014 in spring and early summer (Hernández- Henríquez et al., 2015). 4.4.1.3 Snow cover duration Over the past 30 to 40 years, snow-cover duration (SCD) has declined by 2 to 5 days per decade in the Arctic, including the Baltic area, mostly due to earlier melt onset in spring (Brown

(less than ~50) than between 1950 and 1955 (~400), followed by a period with variations in the range 200–1400 per year. They also mapped the location of icebergs, their debris, and pieces discovered in the Barents Sea in April–May, and compared this with the number found in September over the period 1928–2007. This showed stronger southerly movement during April–May and that icebergs have extended further south over time. The present-day upstream glacier retreat and increased iceberg calving rates are expected to fall when glaciers attain new stable states relative to air temperature (CliC/AMAP/IASC, 2016). Rignot et al. (2011) and Enderlin et al. (2014) have produced the most complete annual iceberg discharge time-series to date. This indicates an average loss of 501±52 Gt/y for the 15-year observation period beginning in 1992. 4.4.1 Snow Snow is an important element of the global climate system and serves as an reflective cover over Arctic land areas and ice surfaces. It has particular importance for the Barents area (see Chapter 2) where the different economic sectors (transportation, infrastructure, tourism/recreation, hydropower production, agriculture) are affected differently by snow. Snow structure (especially internal ice layers) may affect the Arctic ecosystem and reindeer herding through changes in the nature of the habitat and in access to food for grazing animals.Reindeer grazing affects low vegetation and its effect on snow melt, and there is a link to permafrost, heat fluxes, soil moisture, and run-off. Extreme cold outbreaks usually take place in the presence of snow cover, and there have been suggestions of associations with the northern hemisphere winter circulation (Rutgersson et al., 2015). The snow cover reflects much of the incoming solar radiation and so cools the overlying air, but also acts as an insulator by protecting vegetation from frost-damage. Snow is also a heat sink during snow melt, keeping ground temperature near zero, and on the tundra determining whether vegetation is visible. Snow on the ground is also an important reservoir for some pollutants, and is affected by snowfall, temperature and wind. It has socio- economic implications through hazards in terms of avalanches. 4.4.1.1 Snowfall Key elements determining snowfall and snowaccumulation at any place on land are elevation, latitude and proximity to moisture sources.Moisture access is determinedby the general atmospheric and oceanic circulation, as well as local factors (e.g. mountains, lakes,anddistance fromthe coast).SubstantialArcticwarming has been observed since the mid-20th century (Bindoff et al., 2013), with a temperature increase of 0.5°Cper decade and a 2% increase in precipitation per decade over the past 30 years in the Arctic (Karl et al., 2015). Declining sea ice and increased evaporation are contributing to an increase in atmospheric moisture and thereby to increased Arctic precipitation (Bintanja and Selten, 2014).Screen and Simmonds (2012) found a pronounced decline in historic summer snowfall over theArcticOcean andCanadian Arctic Archipelago in the ERA-Interim reanalysis dataset, due to an increase in the proportion of precipitation falling as rain 4.4 Changes in terrestrial conditions