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

January 2009 – April 2013

December 1999 – January 2009

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Figure 4.10 Kernel density estimates for two equally sized intervals of the data set. (Kvammen, 2014; Rojo et al., 2015).

Despite an increase in the frequency of convective clouds over past decades, a shallow stably stratified boundary layers is still thought to remain frequent over the continents and northern islands in the Barents area. Through turbulent convection over the Barents Sea, heat and moisture from the ocean are mixed throughout the low- and mid-troposphere from where they are transferred via the large-scale circulation across the wider Arctic region, causing a rise in temperature and precipitation along the Arctic rim. However, the large-scale circulation is extremely sensitive to perturbations (Rossby waves) within the circulation itself. It is now recognized that warming of the Barents Sea blocks heat transport into the Eurasian continent causing widespread winter cooling (Outten et al., 2013).The most visible and important impact of the convection is connected to increasing atmospheric moisture and developing of convective clouds. The planetary boundary layer plays a strong role in the Arctic. A shallow planetary boundary layer is powerful magnifier of any climate forcing perturbations and anthropogenic pollution hazards. Under conditions with a shallow boundary layer, anthropogenic heat pollution (e.g. urban heat island effects) is significantly enhanced (up to 2°C in Longyearbyen, 6°C in Barrow, and 12°C in Murmansk), with potentially profound environmental implications. Theoretical studies suggest polar low events are initiated by developing boundary layer convection (Økland, 1987; van Delden et al., 2003). Cloudiness and humidity Clouds are associated with weather fronts, synoptic storms, sea ice and planetary boundary layer processes. Clouds are likely to be important for Arctic tourism, as is precipitation. Fog may present challenges in terms of navigation and transport, especially if the droplets are supercooled and freeze on contact with solid surfaces. The intense convection associated with some clouds may generate strong wind gusts, icing and rough surface waves. To date, there is little reliable information concerning past and future trends in cloudiness.

prior to 2009, with peak activity off the coast of Lofoten and Vesterålen, but a recent shift eastward with more occurrences in the central Barents Sea (Figure 4.10). According to the IPCC scenarios, the troposphere in Arctic regions is likely to warm faster than the global average,whereas sea-surface temperatures in the Arctic will rise more slowly, consistent with the concept of a shorter response time for the troposphere.The result will be reduced convective instability, which will lead to fewer polar lows in the future (Zahn and von Storch, 2010).The source area is also likely to shift slightly northward (Zahn and von Storch, 2010). This may lead to fewer polar lows affecting Norwegian coastal waters, but more in the northern and central Barents area. Observational data for the Norwegian and Barents seas show RCMs are able to reproduce the climatology of polar lows and associated extreme events reasonably well in this area (Shkolnik and Efimov, 2013). For future projections of polar low occurrence, the most useful parameters are sea-surface temperature and temperature in the mid-troposphere, since these determine the static stability, which is key to the development of polar lows. The regional flow pattern as represented by the North Atlantic Oscillation (NAO) or other similar indices can be a useful tool. There is also a connection to the planetary boundary layer (i.e. the lower part of the atmosphere between the surface and the upper layers where the air is free to flow, unrestricted by friction from the surface), because this determines the properties of the cold air outbreaks needed for polar low formation. Hence, good knowledge of ice and snow coverage in the Arctic and neighboring areas is essential for understanding polar lows. Planetary boundary layer The atmospheric boundary layer is a region characterized by turbulence and shallow convection, and is influenced by clouds, oceans, and the presence of sea ice. It is the medium through which the atmosphere is coupled to the oceans and a region dominated by a vertical flow of heat and moisture.

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