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  • 1
    Electronic Resource
    Electronic Resource
    Development of Arctic sea-ice organisms under graded snow cover (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 10 (1991), S. 0 
    Details
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: In 1988, the short-term response of sea-ice organisms to manipulated changes in snow cover (no snow cover, natural snow cover, natural snow cover + black foil) was investigated in one ice floe located in the East Greenland Current northwest of Svalbard over a period of three weeks. Autotrophic organisms (flagellates and diatoms) were concentrated in the lowermost 30 cm of the floe. In the field without snow cover, the highest diatom concentrations were observed, consisting nearly entirely of pennate forms, together with a maximum bacterial abundance. The community of larger protozoa and smaller metazoa was dominated by ciliates. Under natural conditions the flora consisted of both flagellates and diatoms, while turbellaria were the dominating animals. In the darkened field, the organism concentrations decreased with time. The results indicate that brine drainage, induced by changes in ice temperature, can reduce concentrations of ice organisms over short time scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-8369.1991.tb00655.x
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    Paper (German National Licenses)
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  • 2
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    Sensitivity of the light field under sea ice to spatially inhomogeneous optical properties and incident light assessed with three-dimensional Monte Carlo radiative transfer simulations (2012)
    ELSEVIER SCIENCE BV
    In:  EPIC3Cold Regions Science and Technology, ELSEVIER SCIENCE BV, pp. 1-11, ISSN: 0165-232X
    Details
    Publication Date: 2014-04-17
    Description: Light transmittance through sea ice is affected by surface cover and ice optical properties in the vicinity of the measurement. We present three-dimensional Monte Carlo simulations of light propagation in sea ice to derive upper bounds on the lateral spread of light. Our results give guidance on equipment design and on the possibility of using one-dimensional light transfer models to describe transmittance. Rules were derived for simple cases of optically homogeneous slabs. In the absence of absorption, 10% and 90% of the flux detected under optically thick, homogeneous ice is incident on the surface within a radius of less than 0.3 and 2.0 times the ice thickness, respectively. Any increase in optical thickness or absorption in the ice will reduce these radii. For example, the wavelength-dependent absorption of ice results in a 20% reduction at 700 nm. Optical anisotropy of the slab was also found to produce potentially significant spatial narrowing of the transmitted light field. In the case of direct sunlight, the photon path is displaced toward the sun relative to the location of the detector. This distortion can reach 1 m or more in optically thick, ponded ice but will be negligible under a surface scattering layer or snow cover. Case studies showed that transmittance of diffuse light in the vicinity of a semi-infinite surface obstruction could be approximated with exponential and error functions. An absorbing cylindrical perturbation of 0.05 m diameter in 1 m thick ice placed 1 m from the point of measurement will absorb less than 1% of the light otherwise registered by the detector. Many results for transmitted light were independent of the mean cosine of the scattering phase function.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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