Influence of melt-pond depth and ice thickness on Arctic sea-ice albedo and light transmittance

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Lu , P , Leppäranta , M , Cheng , B & Li , Z 2016 , ' Influence of melt-pond depth and ice thickness on Arctic sea-ice albedo and light transmittance ' Cold Regions Science and Technology , vol. 124 , pp. 1-10 . DOI: 10.1016/j.coldregions.2015.12.010

Title: Influence of melt-pond depth and ice thickness on Arctic sea-ice albedo and light transmittance
Author: Lu, Peng; Leppäranta, Matti; Cheng, Bin; Li, Zhijun
Contributor: University of Helsinki, Institute for Atmospheric and Earth System Research
Date: 2016-04
Language: eng
Number of pages: 10
Belongs to series: Cold Regions Science and Technology
ISSN: 0165-232X
URI: http://hdl.handle.net/10138/173644
Abstract: Solar radiation drives the melting of Arctic sea ice in summer, but its parameterization in thermodynamic modeling is difficult due to the large variability of the optical properties of sea ice in space and time. Here, a two-stream radiative transfer model was developed for the propagation of solar radiation in ponded sea ice to investigate the dependence of apparent optical properties (AOPs), particularly albedo and transmittance, on sky conditions, pond depth, ice thickness, and the inherent optical properties (IOPs) of ice and water. The results of numerical experiments revealed that decrease in melt-pond albedo during melting results not only from increase in pond depth but also from decrease in underlying ice thickness, and the latter is more important for thin ice with thickness less than 1.5 m. Hence, a parameterized pond albedo as a function of both pond depth and ice thickness is more suitable for thinning Arctic sea ice than the previously used exponential function of pond depth, which is valid for thicker ice. The increase in broadband transmittance during melting can be explained by the decrease in underlying ice thickness, because its dependence on ice thickness is nearly three times stronger than on pond depth. The spectral dependence of the pond albedo on depth is significant only in the 600-900-nm band, while it depends clearly on ice thickness in the 350-600-nm band. The uncertainty resulting from the absorption coefficient of ice is limited, while the effect of scattering in ice is more important, as determined by a sensitivity study on the influence of the IOPs on the AOPs of sea ice. The two-stream model provides a time-efficient parameterization of the AOPs for ponded sea ice, accounting for both absorption and scattering, and has potential for implementation into sea-ice thermodynamic models to explain the role of melt ponds in the summer decay of Arctic sea ice. (C) 2016 Elsevier B.V. All rights reserved.
Subject: Albedo
Melt pond
Transmittance
Radiative transfer
Arctic sea ice
OPTICAL-PROPERTIES
SURFACE ALBEDO
EVOLUTION
FEEDBACK
CLIMATE
MODEL
WATER
SNOW
TRANSMISSION
BASIN
1171 Geosciences
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