Browsing by Subject "Arktis"

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  • Wickman, Mikaela (Helsingin yliopisto, 2018)
    Arktiska rådet som grundades år 1996 är det enda mellanstatliga samarbetsforumet att handskas specifikt med arktiska frågor. Rådet följer med miljöns tillstånd, utger miljöbedömningar om miljöskydd och hållbar utveckling och ger på basis av dessa policyrekommendationer åt medlemsländerna. Medlemsländerna har i alla fall i princip bundit sig till att följa rekommendationerna men rådet har inte mandat att ge juridiskt bindande rekommendationer eller att se till att de verkställs. Nivån på den nationella implementeringen av Arktiska rådets rekommendationer har visat sig vara svag i medlemsländerna men ett område där de gjort framsteg i är att implementera de rekommendationer som rådet gett om åtgärder att minska på utsläpp av svart kol. Finland är ett medlemsland som klarat sig bra med att implementera dessa rekommendationer. Genom en fallstudie över implementeringsprocessen av Arktiska rådets rekommendationer om åtgärder att minska på utsläpp av svart kol i Finland är studiens syfte att skapa en helhetsbild över händelseförloppet av implementeringen för att på så sätt förklara och förstå implementeringsprocessen i Finland. Bakom implementeringen av Arktiska rådets rekommendationer ligger det en policyprocess och genom att granska den är syftet också att systematiskt analysera vilka implementeringsfaktorer som har främjat respektive försvårat implementeringen. Det finns i regel två modeller för att studera implementering, en beslutsorienterad uppifrån-nermodell och en handlingsorienterad nerifrån-uppmodell. Den syntesmodell av de två modellerna som Sabatier utformat bildar tillsammans med Lundquists modell för implementeringsstyrning fallstudiens teoretiska utgångspunkt. Lundquists styrningsmodell utgår ifrån att man vid analys av implementering måste uppmärksamma hur strukturerna och aktörernas förmågor och beteenden påverkar genomförandet. I ett styrningsperspektiv har policytillämparens egenskaper en betydande roll för att förklara avvikelser mellan beslut och utfall vid implementeringen av policy. Studien visar att Finlands förmåga att förstå vad rekommendationerna om svart kol handlar om har främjat implementeringen, likaså Finlands vilja att tillämpa dem. Implementeringen har underlättats av klara och konsekventa målsättningar och av att Arktiska rådet och Finland anser att utsläpp av svart kol är ett problem och att utsläppen måste minskas. Målformuleringar som i början var otydliga har klarnats vilket tyder på att Arktiska rådet som policyförespråkare lärt sig under processens gång. Den arktiska regionen håller på att genomgå en förändring då klimatförändringen syns som ett betydligt varmare klimat och som smältande av havsisen, och då nya ekonomiska möjligheter i samband med det förväntas uppstå. Som ett resultat har intresset mot det arktiska området ökat. Som det centrala samarbetsorganet vad gäller Arktis har betydelsen av Arktiska rådet ökat.
  • Naakka, Tuomas (Ilmatieteen laitos - Finnish Meteorological Institute, 2022)
    Finnish Meteorological Institute Contributions 179
    Water vapour is an effective greenhouse gas, but clouds, which are formed when water vapour condenses into water droplets or ice crystals, may have an even greater effect on radiative energy transfer through the atmosphere. In addition, absorption or release of the latent heat of vaporization and transport of water vapour are part of the heat transport from the Tropics towards the Poles. Thus, atmospheric water vapour greatly affects the energy balance of the atmosphere and is also an important component of the water cycle. This thesis addresses the subject of atmospheric moisture and the processes affecting it in the Arctic and Antarctic. The studies comprising the thesis are mostly based on atmospheric reanalyses. In the polar regions, meteorological observation networks are sparse, due to their remoteness and the harsh environment, and therefore traditional observations have not provided a comprehensive picture of atmospheric conditions in the polar regions. In recent years, atmospheric reanalyses have also become more accurate in remote areas, which has enabled detailed studies of atmospheric moisture in the polar regions. In the polar regions, the mostly negative radiation budget of Earth’s atmosphere-surface system shapes the distribution of water vapour in the atmosphere, especially the vertical structure of specific humidity. The polar regions are sinks for atmospheric water vapour, due to their typically small local evaporation, and even condensation of moisture on the surface. Therefore, moisture transport from the lower latitudes balances the moisture budget in the polar regions. This type of moisture budget favours the formation of specific humidity inversions. Our results show that specific humidity inversions are common in the polar regions, and their occurrence near Earth’s surface is linked with surface conditions: radiative surface cooling, occurrence of temperature inversions in winter and cold sea surfaces or melting of sea ice in summer. Advection of warm, moist air masses over a cold surface in summer is vital for formation of specific humidity inversions. Below the approximately 800-hPa level, interactions between the atmosphere and Earth’s surface clearly affect both the atmospheric moisture content and moisture transport. Our results show that the northward moisture transport near the surface is mostly balanced by southward transport. Moisture transport clearly shapes the spatial distribution of the atmospheric moisture content. Regional trends in atmospheric moisture content in the Arctic are also mostly the results of long-term variations in atmospheric circulation. The negative net radiation budget, weak evaporation and extensive contribution of moisture transport to atmospheric moisture content also characterize moisture conditions in the Antarctic. The results show that, due to geographical conditions, specific humidity inversions in Antarctica are even more persistent than those in the Arctic. This is associated with stronger isolation of air masses in inner Antarctica from advection of warm, moist air masses than in the Arctic. The results also show that when a cold, dry air mass flows from the continent towards the ocean, it undergoes adiabatic warming, which together with downward sensible heat fluxes enables evaporation on Antarctic slopes. Overall, this thesis contributes to our understanding of how the spatial distribution of atmospheric moisture content interacts with moisture transport and with physical processes such as evaporation and condensation in polar regions.
  • Niittynen, Pekka; Heikkinen, Risto K.; Luoto, Miska (2020)
    Proceedings of the National Academy of Sciences of the United States of America 117: 35, 21480-21487
    The Arctic is one of the least human-impacted parts of the world, but, in turn, tundra biome is facing the most rapid climate change on Earth. These perturbations may cause major reshuffling of Arctic species compositions and functional trait profiles and diversity, thereby affecting ecosystem processes of the whole tundra region. Earlier research has detected important drivers of the change in plant functional traits under warming climate, but studies on one key factor, snow cover, are almost totally lacking. Here we integrate plot-scale vegetation data with detailed climate and snow information using machine learning methods to model the responsiveness of tundra communities to different scenarios of warming and snow cover duration. Our results show that decreasing snow cover, together with warming temperatures, can substantially modify biotic communities and their trait compositions, with future plant communities projected to be occupied by taller plants with larger leaves and faster resource acquisition strategies. As another finding, we show that, while the local functional diversity may increase, simultaneous biotic homogenization across tundra communities is likely to occur. The manifestation of climate warming on tundra vegetation is highly dependent on the evolution of snow conditions. Given this, realistic assessments of future ecosystem functioning require acknowledging the role of snow in tundra vegetation models.
  • Kivimäki, Arttu (Helsingin yliopisto, 2021)
    Wind is often difficult to include in microclimatic research due to its high spatial and temporal variability. The development of wind speed and direction measurement methods together with the increase in available surface wind models and computational resources enable wind field simulation on a high temporal and spatial resolution. Winds were measured during summer 2018 in a topographically varying landscape of mostly low vegetation in Finnish Lapland. Six ultrasonic anemometers were placed to measure wind speed and direction in positions of varying topography and vegetation. Based on June 2018 data, topography has a clear effect on wind speeds but the effect of vegetation was not visible from the data. The highest average wind speeds measured on the study area varied between 6.3 m/s – 13.2 m/s, and highest gust wind speeds between 10.1 m/s – 17.1 m/s. The anemometers' data was used in modeling wind fields with WindNinja application to study areas of both topographic and vegetational variation and also to a larger area surrounding the study site. WindNinja is a diagnostic wind model, into which the data were applied as virtual weather stations. The modeling results were compared to measured wind speeds by leave-one-out validation. Spearman correlation coefficients between measured and simulated average wind speeds varied between 0.28 – 0.59, RMSE values between 1.1 – 2.6 m/s and MAE values between 0.8 – 2.0 m/s. The respective values for gust wind simulations were 0.42 – 0.63, 1.6 – 2.7 m/s and 1.2 – 2.1 m/s. Overall WindNinja underpredicted high wind speeds and overpredicted low speeds. In modeling results, topography had a clear effect on regional and local wind fields on all modeling areas Winds were strongest on top of ridges and weakest in depressions. Vegetation had very local effects to wind speed by increasing and lowering it. The results give a good overview of the small-scale windiness variability in the modeling areas. To further examine the micro- and mesoclimatic effects of windiness, the results of this thesis should be combined with other research conducted in the area. WindNinja has potential to further use in high resolution wind modeling, which is an important factor of microclimatic research in the changing climate. However, the software’s graphical user interface is not optimal for modeling longer periods of wind data.