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  • 1
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An infiltration community was the dominating ice algal community in pack-ice off Queen Maud Land, Southern Ocean, in January 1993. The community was dominated by autotrophic processes, and the most common species were the prymnesiophyte Phaeocystis antarctica and the diatoms Chaetoceros neglectus and Fragilariopsis cylindrus. The concentration of chlorophyll a was 1.3–47.9 μg l−1, and the inner part of the community was nitrate depleted. Uptake rates of nitrate, nitrite, ammonium, urea and amino acids were measured using 15N. Nitrate was the major nitrogen source for ice algal growth (67 ± 6% nitrate uptake). It is suggested that % nitrate uptake in the infiltration community decreases during the growth season, from 92% during spring (literature data) to 67% during summer. Scalar irradiance in the infiltration community was high and variable. It reached ca. 2000 μmol m−2 s−1 at some locations, and nitrate uptake rate was potentially photoinhibited at irradiances 〉500 μmol m−2 s−1. Nitrate uptake rate in an average infiltration community (0.6 m of snow cover) was lowered by 13% over a 2-week period due to photoinhibition.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2013-03-13
    Description: ABSTRACT CryoGRID 1.0 provides an equilibrium model of permafrost distribution in Norway at a spatial resolution of 1 km 2 . The approach was forced with gridded data on daily air temperature and snow cover. Ground thermal properties for different bedrock types and sediment covers were derived from surveys and geological maps to yield distributions of thermal conductivity, heat capacity and water content. The distribution of blockfields was derived from satellite images adapting a newly developed classification scheme. The model was evaluated using measured ground surface and ground temperatures, yielding a realistic description of the permafrost distribution in mainland Norway. The model results show that permafrost underlies sites mainly with exposed bedrock or covered by coarse-grained sediments, such as blockfields and coarse tills. In northern Norway, palsa mires are abundant and organic material and vegetation strongly influence the ground thermal regime. Modelling suggests that permafrost in equilibrium with the 1981–2010 climate presently underlies between 6.1 per cent and 6.4 per cent of the total area of mainland Norway, an area significantly smaller than that modelled for the Little Ice Age climate (14%). CryoGRID 1.0 was subsequently forced using output from a regional climate model for the 2071–2100 period, which suggests that severe permafrost degradation will occur, leaving permafrost beneath an area of just 0.2 per cent of mainland Norway. Copyright © 2013 John Wiley & Sons, Ltd.
    Print ISSN: 1045-6740
    Electronic ISSN: 1099-1530
    Topics: Geography , Geosciences
    Published by Wiley-Blackwell
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