Portal de Periódicos da CAPES

Transmission and absorption of solar radiation by Arctic sea ice during the melt season

2008; American Geophysical Union; Volume: 113; Issue: C3 Linguagem: Inglês

10.1029/2006jc003977

2156-2202

Bonnie Light, Thomas C. Grenfell, Donald K. Perovich,

Climate change and permafrost

The partitioning of incident solar radiation between sea ice, ocean, and atmosphere strongly affects the Arctic energy balance during summer. In addition to spectral albedo of the ice surface, transmission of solar radiation through the ice is critical for assessing heat and mass balances of sea ice. Observations of spectral irradiance profiles within and transmittance through ice in the Beaufort Sea during the summer of 1998 during the Surface Heat Budget of the Arctic Ocean (SHEBA) are presented. Sites representative of melting multiyear and first‐year ice, along with ponded ice were measured. Observed spectral irradiance extinction coefficients (K λ ) show broad minima near 500 nm and strong increases at near‐infrared wavelengths. The median K λ at 600 nm for the bare ice cases is close to 0.8 m −1 and about 0.6 m −1 for ponded ice. Values are considerably smaller than the previously accepted value of 1.5 m −1 . Radiative transfer models were used to analyze the observations and obtain inherent optical properties of the ice. Derived scattering coefficients range from 500 m −1 to 1100 m −1 in the surface layer and 8 to 30 m −1 in the ice interior. While ponded ice is known to transmit a significant amount of shortwave radiation to the ocean, the irradiance transmitted through bare, melting ice is also shown to be significant. The findings of this study predict 3–10 times more solar radiation penetrating the ice cover than predicted by a current GCM (CCSM3) parameterization, depending on ice thickness, pond coverage, stage of the melt season, and specific vertical scattering coefficient profile.