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

Abstract

AbstractTo 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 Hs and the scattering coefficient σs of the ice lid are altered. Variations in the spectral albedo αλ and transmittance Tλ due to Hs 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 σs·Hs. Good agreement between field measurements and our model simulations is found. The number σs·Hs is confirmed to be a good index showing that the influence of an ice lid with σs·Hs < 0.5 is negligible. This criterion can be easily performed during field observations through visually judging whether the ice lid has significantly changed the color of liquid melt ponds or not.