Cytisus scoparius : a genetic and historical analysis of introduction history in Norway

Cytisus scoparius is an invasive species threatening the local flora where the shrub is introduced. Studies show that the shrub spreads rapidly and has damaging effects in areas where the plant is considered invasive. Cytisus scoparius has been considered native in Norway but may threaten vulnerable habitats such as coastal heathlands, calling for a regulation of the shrub’s expansion. This study uses molecular and historical analysis to investigate if in fact C. scoparius is native to the Norwegian flora or if it is introduced through human actions. 28 Norwegian C. scoparius populations were sampled and compared with 27 non-Norwegian samples and 22 Norwegian herbaria samples. The samples were grouped into nine haplotypes and analyzed to find if there is a genetically distinct variation of C. scoparius in Norway, and to decide whether there has been a single or multiple introductions to Norway, and if there is a traceable introduction path. My results reveal high genetic variation among all samples. The nine haplotypes identified are scattered over a large area, which indicates multiple introductions to Norway and makes it difficult to trace possible introduction routes.M-BIO

Observed anomalous atmospheric patterns in summers of unusual Arctic sea ice melt

The Arctic sea ice retreat has accelerated over the last decade. The negative trend is largest in summer, but substantial interannual variability still remains. Here we explore observed atmospheric conditions and feedback mechanisms during summer months of anomalous sea ice melt in the Arctic. Compositing months of anomalous low and high sea ice melt over 1979–2013, we find distinct patterns in atmospheric circulation, precipitation, radiation, and temperature. Compared to summer months of anomalous low sea ice melt, high melt months are characterized by anomalous high sea level pressure in the Arctic (up to 7 hPa), with a corresponding tendency of storms to track on a more zonal path. As a result, the Arctic receives less precipitation overall and 39% less snowfall. This lowers the albedo of the region and reduces the negative feedback the snowfall provides for the sea ice. With an anticyclonic tendency, 12 W/m2 more incoming shortwave radiation reaches the surface in the start of the season. The melting sea ice in turn promotes cloud development in the marginal ice zones and enhances downwelling longwave radiation at the surface toward the end of the season. A positive cloud feedback emerges. In midlatitudes, the more zonally tracking cyclones give stormier, cloudier, wetter, and cooler summers in most of northern Europe and around the Sea of Okhotsk. Farther south, the region from the Mediterranean Sea to East Asia experiences significant surface warming (up to 2.4◦C), possibly linked to changes in the jet stream

Nearshore wave forecasting and hindcasting by dynamical and statistical downscaling

A high-resolution nested WAM/SWAN wave model suite aimed at rapidly establishing nearshore wave forecasts as well as a climatology and return values of the local wave conditions with Rapid Enviromental Assessment (REA) in mind is described. The system is targeted at regions where local wave growth and partial exposure to complex open-ocean wave conditions makes diagnostic wave modelling difficult. SWAN is set up on 500 m resolution and is nested in a 10 km version of WAM. A model integration of more than one year is carried out to map the spatial distribution of the wave field. The model correlates well with wave buoy observations (0.96) but overestimates the wave height somewhat (18%, bias 0.29 m). To estimate wave height return values a much longer time series is required and running SWAN for such a period is unrealistic in a REA setting. Instead we establish a direction-dependent transfer function between an already existing coarse open-ocean hindcast dataset and the high-resolution nested SWAN model. Return values are estimated using ensemble estimates of two different extreme-value distributions based on the full 52 years of statistically downscaled hindcast data. We find good agreement between downscaled wave height and wave buoy observations. The cost of generating the statistically downscaled hindcast time series is negligible and can be redone for arbitrary locations within the SWAN domain, although the sectors must be carefully chosen for each new location. The method is found to be well suited to rapidly providing detailed wave forecasts as well as hindcasts and return values estimates of partly sheltered coastal regions.Comment: 20 pages, 7 figures and 2 tables, MREA07 special issue on Marine rapid environmental assessmen

Cytisus scoparius : a genetic and historical analysis of introduction history in Norway

Cytisus scoparius is an invasive species threatening the local flora where the shrub is introduced. Studies show that the shrub spreads rapidly and has damaging effects in areas where the plant is considered invasive. Cytisus scoparius has been considered native in Norway but may threaten vulnerable habitats such as coastal heathlands, calling for a regulation of the shrub’s expansion. This study uses molecular and historical analysis to investigate if in fact C. scoparius is native to the Norwegian flora or if it is introduced through human actions. 28 Norwegian C. scoparius populations were sampled and compared with 27 non-Norwegian samples and 22 Norwegian herbaria samples. The samples were grouped into nine haplotypes and analyzed to find if there is a genetically distinct variation of C. scoparius in Norway, and to decide whether there has been a single or multiple introductions to Norway, and if there is a traceable introduction path. My results reveal high genetic variation among all samples. The nine haplotypes identified are scattered over a large area, which indicates multiple introductions to Norway and makes it difficult to trace possible introduction routes.M-BIO