Search results for "arctic"
showing 10 items of 565 documents
Concentrations, composition, and sources of ice-nucleating particles in the Canadian High Arctic during spring 2016
2019
Modelling studies suggest that the climate and the hydrological cycle are sensitive to the concentrations of ice-nucleating particles (INPs). However, the concentrations, composition, and sources of INPs in the atmosphere remain uncertain. Here, we report daily concentrations of INPs in the immersion freezing mode and tracers of mineral dust (Al, Fe, Ti, and Mn), sea spray aerosol (Na+ and Cl−), and anthropogenic aerosol (Zn, Pb, NO3-, NH4+, and non-sea-salt SO42-) at Alert, Canada, during a 3-week campaign in March 2016. In total, 16 daily measurements of INPs are reported. The average INP concentrations measured in the immersion freezing mode were 0.005±0.002, 0.020±0.004, and 0.186±0.040…
Reproductive strategy as a piece of the biogeographic puzzle: a case study using Antarctic sea stars (Echinodermata, Asteroidea)
2017
13 pages; International audience; AimTo describe and analyse asteroid biogeographic patterns in the Southern Ocean (SO) and test whether reproductive strategy (brooder versus broadcaster) can explain distribution patterns at the scale of the entire class. We hypothesize that brooding and broadcasting species display different biogeographic patterns.LocationSouthern Ocean, south of 45 °S.MethodsOver 14,000 asteroid occurrences are analysed using bootstrapped spanning network (BSN), non-metrical multidimensional scaling (nMDS) and clustering to uncover the spatial structure of faunal similarities among 25 bioregions.ResultsMain biogeographic patterns are congruent with previous works based on…
Intraspecific Differences in Spectral Reflectance Curves as Indicators of Reduced Vitality in High-Arctic Plants
2017
Remote sensing is a suitable candidate for monitoring rapid changes in Polar regions, offering high-resolution spectral, spatial and radiometric data. This paper focuses on the spectral properties of dominant plant species acquired during the first week of August 2015. Twenty-eight plots were selected, which could easily be identified in the field as well as on RapidEye satellite imagery. Spectral measurements of individual species were acquired, and heavy metal contamination stress factors were measured contemporaneously. As a result, a unique spectral library of dominant plant species, heavy metal concentrations and damage ratios were achieved with an indication that species-specific chan…
Ecotoxicity assessment of natural attenuation effects at a historical dumping site in the western Baltic Sea.
2005
During the late 1950s and early 1960s of the past century, industrial waste material highly enriched in various contaminants (heavy metals, PAHs) was dumped in the inner Mecklenburg Bay, western Baltic Sea. Large-scale shifts in the spatial distribution of heavy metals in surface sediments were mapped by geochemical monitoring in the mid-1980s and 12 years later in 1997. A further study in 2001 was designed to investigate the small-scale spatial distribution of contaminants inside, on top of, and around the historical dumping ground and to examine possible effects to benthic organisms (Arctica islandica, microbiological toxicity tests). The site is located within an area characterized by a …
Widespread persistent polar stratospheric ice clouds in the Arctic
2016
Abstract. Despite a general decline in ozone depleting substances in the stratosphere due to the multi-national commitment to substantially reduce the emissions of their precursors, the magnitude of Arctic polar ozone loss has not decreased in recent years. Thus new observations at cold conditions can help to enhance our knowledge of polar stratospheric cloud (PSC) formation and life cycle which is of relevance for Arctic ozone loss. In the unique winter 2015/16, cold and persistent areas with temperatures below the ice frost point Tice developed in the Arctic stratosphere, caused by reduced perturbations of the polar vortex through planetary waves. Due to these extreme conditions, unpreced…
Temperature-related changes in polar cyanobacterial mat diversity and toxin production
2012
This study documents the effects of warming on cyanobacterial mats from the Arctic and Antarctica. It describes toxin production in such mats and provides experimental evidence that increased temperatures could shift mat cyanobacterial species diversity from cold-loving species towards predominance of cold-tolerant and toxin-producing species.
Response to reindeer grazing removal depends on soil characteristics in low Arctic meadows
2014
In Arctic tundra, grazing is expected to exert a positive influence on microbial activity thus enhancing nutrient cycling and promoting the presence of high productive graminoids. We investigated the changes occurring in two low Arctic meadow sites after 10 years exclusion from grazing. We compared plant, soil fauna and microbial community composition, extracellular enzymes activities, and soil nutrients in ungrazed and adjacent grazed area in two low Arctic meadows. The two closely located experimental sites were both dominated by the common grass Deschampsia flexuosa which covered more than 50% of the meadows. Plant community was affected significantly by site and grazing, but the effect …
From clear lakes to murky waters – tracing the functional response of high-latitude lake communities to concurrent ‘greening’ and ‘browning’
2019
Climate change and the intensification of land use practices are causing widespread eutrophication of subarctic lakes. The implications of this rapid change for lake ecosystem function remain poorly understood. To assess how freshwater communities respond to such profound changes in their habitat and resource availability, we conducted a space-for-time analysis of food-web structure in 30 lakes situated across a temperature-productivity gradient equivalent to the predicted future climate of subarctic Europe (temperature +3 degrees C, precipitation +30% and nutrient +45 mu g L-1 total phosphorus). Along this gradient, we observed an increase in the assimilation of pelagic-derived carbon from…
Statistical upscaling of ecosystem CO2 fluxes across the terrestrial tundra and boreal domain: Regional patterns and uncertainties
2021
The regional variability in tundra and boreal carbon dioxide (CO2) fluxes can be high, complicating efforts to quantify sink-source patterns across the entire region. Statistical models are increasingly used to predict (i.e., upscale) CO2 fluxes across large spatial domains, but the reliability of different modeling techniques, each with different specifications and assumptions, has not been assessed in detail. Here, we compile eddy covariance and chamber measurements of annual and growing season CO2 fluxes of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem exchange (NEE) during 1990–2015 from 148 terrestrial high-latitude (i.e., tundra and boreal) sites to a…
The effects of oil spills on marine fish: Implications of spatial variation in natural mortality.
2017
The effects of oil spills on marine biological systems are of great concern, especially in regions with high biological production of harvested resources such as in the Northeastern Atlantic. The scientific studies of the impact of oil spills on fish stocks tend to ignore that spatial patterns of natural mortality may influence the magnitude of the impact over time. Here, we first illustrate how spatial variation in natural mortality may affect the population impact by considering a thought experiment. Second, we consider an empirically based example of Northeast Arctic cod to extend the concept to a realistic setting. Finally, we present a scenario-based investigation of how the degree of …