Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-117
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Aug 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).
The color of melt ponds on Arctic sea ice
Peng Lu1, Matti Leppäranta2, Bin Cheng3, Zhijun Li1, Larysa Istomina4, and Georg Heygster4 1State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China
2Department of Physics, University of Helsinki, Helsinki, Fi-00014, Finland
3Finnish Meteorological Institute, Helsinki, Fi-00101, Finland
4Institute of Environmental Physics, University of Bremen, Bremen, 28359, Germany
Abstract. Pond color, which creates the visual appearance of melt ponds on Arctic sea ice in summer, is quantitatively investigated in this study. A two-stream radiative transfer model is used for ponded sea ice: the upwelling irradiance from the pond surface is determined, and then the upwelling spectrum is transformed into the RGB color space through a colorimetric method. The dependence of pond color on various factors such as water and ice properties and incident solar radiation is investigated. The results reveal that increasing underlying ice thickness Hi enhances both the green and blue components of pond color, whereas the red component is mostly sensitive to Hi for thin ice (Hi < 1.5 m) and to pond depth Hp for thick ice (Hi > 1.5 m), similar to the behavior of melt-pond albedo. The distribution of the incident solar spectrum F0 with wavelength affects the pond color rather than its level. The pond color changes from dark blue to brighter blue with increasing scattering in ice, but the influence of absorption in ice on pond color is limited. The pond color reproduced by the model agrees well with field observations on Arctic sea ice in summer, which supports the validity of this study. More importantly, pond color has been confirmed to contain information about meltwater and underlying ice, and therefore it can be used as an index to retrieve Hi and Hp. The results show that retrievals of Hi for thin ice agree better with field measurements than retrievals for thick ice, but that retrievals of Hp are not good. Color has been shown to be a new potential method to obtain ice thickness information, especially for melting sea ice in summer, although more validation data and improvements to the radiative transfer model will be needed in future.

Citation: Lu, P., Leppäranta, M., Cheng, B., Li, Z., Istomina, L., and Heygster, G.: The color of melt ponds on Arctic sea ice, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-117, in review, 2017.
Peng Lu et al.
Peng Lu et al.

Data sets

Spectral albedo, water depth and ice thickness within melt ponds measured during POLARSTERN cruise ARK-XXVII/3 (IceArc) in 2012
L. Istomina, M. Nicolaus, and D. K. Perovich
https://doi.org/10.1594/PANGAEA.876210
Peng Lu et al.

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Short summary
It is the first time that the color of melt ponds on Arctic sea ice was quantitatively and thoroughly investigated. We answer the question why the color of melt ponds can change and what are the physical and optical reasons leading to such changes. More importantly, melt-pond color was provided to be potential data to retrieve the ice thickness, especially under the summer conditions when other methods such as remote sensing are unavailable.
It is the first time that the color of melt ponds on Arctic sea ice was quantitatively and...
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