As the climate warms, Arctic bumblebee species face the loss of habitat and must deal with increased competition from southern species tracking their thermal and habitat niches north, for example Bombus terrestris. Previous studies demonstrate that bumblebees follow Bergmann’s rule, i.e., larger body sizes at higher latitudes, despite bumblebees not being considered truly ectothermic, as they can generate heat through muscular activity (i.e., beating their wings). This study seeks to confirm and understand the relationship between body size and temperature using an elevational gradient as a proxy for climate. In this study, I examined 13 plots (420-1164 m.a.s.l.) set along the 3.4 km transect up the slope of Mt. Nuolja in Abisko National Park, Sweden. For body size, I chose to use the commonly accepted proxy distance between the base of the wings (i.e., intertegular distance). For temperature, I chose the mean temperature at time of visitation. Results show that climate is a significant explanatory variable for bumblebee body size, with an overall increasing body size with increasing elevation (i.e., colder climate), although most of the variance is explained by caste, i.e., queens having a larger body size than workers. Body size also shows some correlation with day of capture, which can be explained by changes in environmental conditions (e.g., temperature, flowering plant species) during the growing season experienced by the different emerging times for the castes. Given that caste was the most useful explanatory variable for body size, future studies could look at a larger environmental gradient, for example, by sampling at multiple locations along the entire Scandes mountain range to see if the effects found are localized. Further, specific habitat and specific traits of preferred plants may also help to elucidate body-size differences between species and castes. For example, many bumblebee species’ castes emerge at a specific time of year when only certain flowering plant species in specific habitats are available. This important research would also help to illuminate whether bumblebees and the species of plants they pollinate remain synchronous as climate warming accelerates. Nevertheless, my results show an overall positive relationship between bumblebee body size and elevation, indicating that a warming climate will result in reduced body sizes among bumble bee species. Future studies will have to investigate what consequences this will have for Arctic bumblebee populations – and for the plants that rely on bumblebee visits for their pollination.

Insect pollinators serve a critical role in maintaining plant biodiversity and are especially susceptible to changes within their environment. To study the possible effects of seasonal variation in temperature, as well as climatic temperature increase on the plant-pollinator community, the relationship between bumblebee and flowering plant traits along an elevational gradient, representing warming-induced changes in plant community, were examined. Two hypotheses were tested; 1) if plant traits can predict visiting bumblebee proboscis length, and 2) if the relationship between plant traits and proboscis length is influenced by elevation, and the progression of the growing season. The study took place along an elevational gradient on Mt. Nuolja in Abisko National Park, Sweden. During surveys bumblebees were caught and measured. Flowers visited by captured bumblebees were collected, categorized by restrictiveness (i.e., whether or not the flower require a certain proboscis length, in order to access the nectar and pollen rewards) and floral traits measured (e.g., petal length). The results revealed that petal length was a significant predictor of bumblebee proboscis length, when taking restrictiveness into account. Furthermore, the relationship became weaker with increasing elevation for restrictive flowers but stronger for unrestrictive flowers. These findings show that trait-matching between bumblebees and flowers is an influential factor for flower selection and is affected by climatic temperature. This highlights the importance of considering individual-level traits when studying plant preference and creates a framework for assessing plant-pollinator networks. Future studies should examine additional traits that could explain the apparent size matching between unrestrictive flowers and proboscis.

No description available.

La neige est une composante essentielle du système climatique arctique. Au nord de l'Eurasie et de l'Amérique du Nord, la couverture neigeuse est présente de 7 à 10 mois par an et son extension saisonnière maximale représente plus de 40% de la surface terrestre de l'hémisphère nord. La neige affecte une variété de processus climatiques et de rétroactions aux hautes latitudes. Sa forte réflectivité et sa faible conductivité thermique ont un effet de refroidissement et modulent la rétroaction neige-albédo. Sa contribution au bilan radiatif de la Terre est comparable à celle de la banquise. De plus, en empêchant d'importantes pertes d'énergie du sol sous-jacent, la neige limite la progression de la glace et le développement du pergélisol saisonnier. Réserve d'eau naturelle, la neige joue un rôle essentiel dans le cycle hydrologique aux hautes latitudes, notamment en ce qui concerne l'évaporation et le ruissellement. La neige est l'une des composantes du système climatique présentant la plus forte variabilité. Le réchauffement de l'Arctique étant deux fois plus rapide que celui du reste du globe, la variabilité présente et future des caractéristiques de la neige est cruciale pour une meilleure compréhension des processus et des changements climatiques.Cependant, notre capacité à observer l'Arctique terrestre étant limitée, les modèles climatiques jouent un rôle clé dans notre aptitude à comprendre les processus liés à la neige. À cet égard, la représentation des rétroactions associées à la neige dans les modèles climatiques, en particulier pendant les saisons intermédiaires (lorsque la couverture neigeuse de l'Arctique présente la plus forte variabilité), est primordiale.Notre étude porte principalement sur la représentation de la neige terrestre arctique dans les modèles de circulation générale issus du projet CMIP5 (Coupled Model Intercomparison Project) au cours du printemps (mars-avril) et de l’automne (octobre-novembre) de 1979 à 2005. Les caractéristiques de la neige des modèles de circulation générale ont été validées par rapport aux mesures de neige in situ, ainsi qu’à des produits satellitaires et à des réanalyses.Nous avons constaté que les caractéristiques de la neige dans les modèles ont un biais plus marqué au printemps qu'en automne. Le cycle annuel de la couverture neigeuse est bien reproduit par les modèles. Cependant, les cycles annuels d'équivalent en eau de la neige et de sa profondeur sont largement surestimés par les modèles, notamment en Amérique du Nord. Il y a un meilleur accord entre les modèles et les observations dans la position de la marge de neige au printemps plutôt qu'en automne. Les amplitudes de variabilité interannuelle pour toutes les variables de la neige sont nettement sous-estimées par la plupart des modèles CMIP5. Pour les deux saisons, les tendances des variables de la neige dans les modèles sont principalement négatives, mais plus faibles et moins significatives que celles observées. Les distributions spatiales des tendances de la couverture neigeuse sont relativement bien reproduites par les modèles, toutefois, la distribution spatiale des tendances en équivalent-eau et en profondeur de la neige présente de fortes hétérogénéités régionales.Enfin, nous concluons que les modèles CMIP5 fournissent des informations précieuses sur les caractéristiques de la neige en Arctique terrestre, mais qu’ils présentent encore des limites. Il y a un manque d’accord entre l’ensemble des modèles sur la distribution spatiale de la neige par rapport aux observations et aux réanalyses. Ces écarts sont particulièrement marqués dans les régions où la variabilité de la neige est la plus forte. Notre objectif dans cette étude était d'identifier les circonstances dans lesquelles ces modèles reproduisent ou non les caractéristiques observées de la neige en Arctique. Nous attirons l’attention de la communauté scientifique sur la nécessité de prendre compte nos résultats pour les futures études climatiques. / Snow is a critical component of the Arctic climate system. Over Northern Eurasia and North America the duration of snow cover is 7 to 10 months per year and a maximum snow extension is over 40% of the Northern Hemisphere land each year. Snow affects a variety of high latitude climate processes and feedbacks. High reflectivity of snow and low thermal conductivity have a cooling effect and modulates the snow-albedo feedback. A contribution from terrestrial snow to the Earth’s radiation budget at the top of the atmosphere is close to that from the sea ice. Snow also prevents large energy losses from the underlying soil and notably the ice growth and the development of seasonal permafrost. Being a natural water storage, snow plays a critical role in high latitude hydrological cycle, including evaporation and run-off. Snow is also one of the most variable components of climate system. With the Arctic warming twice as fast as the globe, the present and future variability of snow characteristics are crucially important for better understanding of the processes and changes undergoing with climate. However, our capacity to observe the terrestrial Arctic is limited compared to the mid-latitudes and climate models play very important role in our ability to understand the snow-related processes especially in the context of a warming cryosphere. In this respect representation of snow-associated feedbacks in climate models, especially during the shoulder seasons (when Arctic snow cover exhibits the strongest variability) is of a special interest.The focus of this study is on the representation of the Arctic terrestrial snow in global circulation models from Coupled Model Intercomparison Project (CMIP5) ensemble during the melting (March-April) and the onset (October-November) season for the period from 1979 to 2005. Snow characteristics from the general circulation models have been validated against in situ snow measurements, different satellite-based products and reanalyses.We found that snow characteristics in models have stronger bias in spring than in autumn. The annual cycle of snow cover is well captured by models in comparison with observations, however, the annual cycles of snow water equivalent and snow depth are largely overestimated by models, especially in North America. There is better agreement between models and observations in the snow margin position in spring rather than in autumn. Magnitudes of interannual variability for all snow characteristics are significantly underestimated in most CMIP5 models compared to observations. For both seasons, trends of snow characteristics in models are primarily negative but weaker and less significant than those from observations. The patterns of snow cover trends are relatively well reproduced in models, however, the spatial distribution of trends for snow water equivalent and snow depth display strong regional heterogeneities.Finally, we have concluded CMIP5 general circulation models provides valuable information about the snow characteristics in the terrestrial Arctic, however, they have still limitations. There is a lack of agreement among the ensemble of models in the spatial distribution of snow compared to the observations and reanalysis. And these discrepancies are accentuated in regions where variability of snow is higher in areas with complex terrain such as Canada and Alaska and during the melting and the onset season. Our goal in this study was to identify where and when these models are or are not reproducing the real snow characteristics in the Arctic, thus we hope that our results should be considered when using these snow-related variables from CMIP5 historical output in future climate studies.

Land ice is losing mass to the worlds oceans at an accelerated rate. The worlds glaciers contain much less ice than the ice sheets but contribute equally to eustatic sea level rise and are expected to continue to do so over the coming centuries if global temperatures continue to rise. It is therefore important to characterize the mass balance of these glaciers and its relationship to climate trends and variability. In the Canadian High Arctic, analysis of long-term surface mass balance records shows a shift to more negative mass balances after 1987 and is coincident with a change in the mean location of the July circumpolar vortex, a mid-troposphere cyclonic feature known to have a strong influence on Arctic summer climate. Since 1987 the occurrence of July vortices centered in the Eastern Hemisphere have increased significantly. This change is associated with an increased frequency of tropospheric ridging over the Canadian High Arctic, higher surface air temperatures, and more negative glacier mass balance. However, regional scale mass balance modeling is needed to determine whether or not the long-term mass balance measurements in this region accurately reflect the mass balance of the entire Canadian High Arctic. The Canadian High Arctic is characterized by high relief and complex terrain that result in steep horizontal gradients in surface mass balance, which can only be resolved if models are run at high spatial resolutions. For such runs, models often require input fields such as air temperature that are derived by downscaling of output from climate models or reanalyses. Downscaling is often performed using a specified relationship between temperature and elevation (a lapse rate). Although a constant lapse rate is often assumed, this is not well justified by observations. To improve upon this assumption, near-surface temperature lapse rates during the summer ablation season were derived from surface measurements on 4 Arctic glaciers. Near-surface lapse rates vary systematically with free-air temperatures and are less steep than the free-air lapse rates that have often been used in mass balance modeling. Available observations were used to derive a new variable temperature downscaling method based on temperature dependent daily lapse rates. This method was implemented in a temperature index mass balance model, and results were compared with those derived from a constant linear lapse rate. Compared with other approaches, model estimates of surface mass balance fit observations much better when variable, temperature dependent lapse rates are used. To better account for glacier-climate feedbacks within mass balance models, more physically explicit representations of snow and ice processes must be used. Since absorption of shortwave radiation is often the single largest source of energy for melt, one of the most important parameters to model correctly is surface albedo. To move beyond the limitations of empirical snow and ice albedo parameterizations often used in surface mass balance models, a computationally simple, theoretically-based parameterization for snow and ice albedo was developed. Unlike previous parameterizations, it provides a single set of equations for the estimation of both snow and ice albedo. The parameterization also produces accurate results for a much wider range of snow, ice, and atmospheric conditions.

No description available.

Identifying the drivers of Arctic climate variability is essential for understanding the recent rapid changes in local climate and determining the mechanisms that cause them. Remote tropical sea surface temperatures (SST) have been identified in previous studies as having contributed to the recent positive trends in surface temperature and geopotential height at 200 hPa over north Canada and Greenland (1979-2012) through poleward propagating Rossby waves. However, the source and direction of wave propagation on to north Canada and Greenland (NCG) differs across climate datasets indicating that there are still uncertainties surrounding the mechanisms for how the tropics influence the NCG climate. This thesis aims to further investigate the robustness of the trends over NCG and understand how circulation in this region responds to imposed tropical SST perturbations. The eddy 200 hPa geopotential height (Z200) trends over NCG are assessed in a number of different datasets and compared to the response of eddy Z200 over NCG to imposed tropical SST perturbations in a number of sensitivity studies using the HadGEM3 atmosphere-only model. These model experiments are forced with observed differences in SSTs from the beginning and end of the satellite record (1979-1988 and 2003-2012), with spatial perturbations for [i] the entire tropics, [ii] global SSTs, [iii] the tropical Pacific only, [iv] the tropical Atlantic SST only, [v] the tropical Indian Ocean only. The positive spatial trends of eddy Z200 over NCG from ERA-Interim reanalysis is largely captured in ensemble means of two available climate datasets, UPSCALE and AMIP, indicating that this is a robust climate pattern, however, these trends appear to be stronger in the latter part of the record specifically over the UPSCALE period (1985 to 2011). The model sensitivity studies show that a negative eddy Z200 anomaly over NCG was found in response to all imposed tropical SST perturbations (2003-2012) relative to a background state (1979-1988). This was due a stationary trough over the region that was able to intensify in response to a lack of a strong anomalous wave forcing from changes in mid-tropospheric temperature and zonal winds. The forcing from the tropical Atlantic, relative to the other tropical ocean basins, resulted in the largest eddy Z200 response over NCG, indicating its dominance in forcing the large scale tropical signal. The influence of extratropical SST perturbations relative to tropical SST perturbations were also investigated and it was demonstrated that this negative anomaly is largely driven by the change in tropical sea surface temperatures.

Det finns evidens som bekräftar fördelarna med att barn ägnar sig åt aktiva skoltransporter(AST). Trots detta har andelen barn som ägnar sig åt AST radikalt minskat under de senasteårtiondena. Vårdnadshavare är de som fattar beslut gällande sina barn, vilket skulle kunna spela en viktig roll när det kommer till AST, då deras attityder gentemot detta kan påverka huruvida barnet ägnar sig åt AST eller inte. Syftet med denna studie var att undersöka de attityder vårdnadshavare till barn i årskurs 1–6, boende i ett arktiskt klimat har till aktiva skoltransporter. Studien utgick från ett befintligt projekt som ämnade att främja AST i en kommun i norra Sverige och utfördes med en kvalitativ metod och deskriptiv design för att besvara syftet. Datainsamlingen bestod av individuella intervjuer tillsammans med sex deltagare. Intervjuerna utfördes utifrån en förberedd intervjuguide och frågeställningarna utgick ifrån theory of planned behavior. En manifest analys av den insamlade datan gjordes genom fem steg, vilket resulterade i att en huvudkategori växte fram, Rörelse – en gemensam målsättning, samt tre underkategorier; Ett hållbart liv (1), Olika former av trygghet (2), Inre och yttre påverkan (3). Resultatet indikerar att vårdnadshavare anser att en hållbar vardag, hälsa och miljö är viktigt samt att olika former av trygghet värderas högt och kan påverkas av en rad olika faktorer. Resultatet indikerar att vårdnadshavares egna erfarenheter påverkar inställningen till AST samt att uppfattningar av omgivningens värderingar och normer gällande AST på ett omedvetet plan kan ha inflytande på den egna inställningen till skoltransportens genomförande. Hälsopromotiva insatser som ökar andelen barn som ägnar sig åt AST kan vara en del i skapandet av normer som resulterar i att andelen transporter med bil minskar. Vilket utöver att den fysiska aktiviteten ökar också skulle gynna miljön och skapa tryggare skolvägar. / There is evidence to confirm the benefits of children engaging in active school transportation (AST). Despite this, the proportion of children engaged in AST has radically decreased in recent decades. Guardians are the ones who make decisions regarding their children, which could play an important role when it comes to AST, as their attitudes towards AST can affect whether the child engages in AST or not. The aim of this study was to investigate the attitudes towards active school transportation among guardians of children in grades 1-6, living in an arctic climate. The study was based on an existing project that aimed to promote AST in a municipality in northern Sweden and was performed with a qualitative method and descriptive design to answer the purpose. The data collection consisted of individual interviews together with six participants. The interviews were conducted from a prepared interview guide and the questions were based on the theory of planned behavior. A manifest analysis of the collected data was done through five steps, which resulted in a main category: Movement - a common goal, and three subcategories; A sustainable life (1), Different forms of safety (2), Internal and external influences (3). The results indicate that guardians believe that a sustainable everyday life, health and environment are important and that various forms of safety are highly valued and can be affected by several different factors. The results indicatethat the guardian's own experiences affect their attitude towards AST, and that the perceptions of the environment's values and norms regarding AST on an unconscious level can have an influence on the guardian's own attitude to the implementation of school transport. Health-promoting initiatives that increase the proportion of children who engage in AST can be a part of the establishing of norms that result in a reduction of the proportion of transport by car. Which in addition to increasing physical activity would also benefit the environment and create safer school roads.