Impact of a Surface Ice Lid on the Optical Properties of Melt Ponds

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Lu , P , Cao , X , Wang , Q , Leppäranta , M , Cheng , B & Li , Z 2018 , ' Impact of a Surface Ice Lid on the Optical Properties of Melt Ponds ' , Journal of Geophysical Research : Oceans , vol. 123 , no. 11 , pp. 8313-8328 . https://doi.org/10.1029/2018JC014161

Title: Impact of a Surface Ice Lid on the Optical Properties of Melt Ponds
Author: Lu, P.; Cao, X.; Wang, Q.; Leppäranta, M.; Cheng, B.; Li, Z.
Contributor: University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
Date: 2018-11
Language: eng
Number of pages: 16
Belongs to series: Journal of Geophysical Research : Oceans
ISSN: 2169-9275
URI: http://hdl.handle.net/10138/301858
Abstract: To investigate the influence of a surface ice lid on the optical properties of a melt pond, a radiative transfer model was employed that includes four plane-parallel layers: an ice lid, a melt pond, the underlying ice, and the ocean beneath the ice. The thickness H-s and the scattering coefficient sigma(s) of the ice lid are altered. Variations in the spectral albedo and transmittance T due to H-s for a transparent ice lid are limited, and scattering in the ice lid has a pronounced impact on the albedo of melt ponds as well as the vertical distribution of spectral irradiance in ponded sea ice. The thickness of the ice lid determines the amount of solar energy absorbed. A 2-cm-thick ice lid can absorb 13% of the incident solar energy, half of the energy absorbed by a 30-cm-deep meltwater layer below the lid. This has an influence on the thermodynamics of melting sea ice. The color and spectral albedo of refreezing melt ponds depend on the value of the dimensionless number sigma(s) H- s. Good agreement between field measurements and our model simulations is found. The number sigma(s) H- s is confirmed to be a good index showing that the influence of an ice lid with sigma(s) H- s Plain Language Summary Melt ponds are pools of open water that form on sea ice in the warm months of the Arctic Ocean, and they will frequently be refrozen due to loss of heat and then covered by an ice lid or snow even in summer. This lid is very important to the optical properties of melt ponds. If the ice lid is very thin, the change in the reflective characteristics of the melt pond is minimal; that is, the influence of the ice lid is negligible. If snow accumulates on the ice lid, the reflective characteristics of the melt pond change completely. How about the situation between the above two extreme cases? In this study, we find that a dimensionless number is a good index to quantify the impact of the ice lid. Visual inspections on the color of refreezing melt ponds also help to judge the significance of the influence of the ice lid. This will allow for an accurate estimation on the role of surface ice lid during field investigations on the optical properties of melt ponds.
Subject: melt ponds
Arctic sea ice
radiative transfer
refreezing
numerical simulation
ARCTIC SEA-ICE
RADIATIVE-TRANSFER
MONTE-CARLO
BALANCE
ALBEDO
ENERGY
WATER
TRANSMISSION
VALIDATION
EVOLUTION
1172 Environmental sciences
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