Observations of the optical properties of the upper ocean during SHEBA

The beam attenuation and absorption coefficients at nine wavelengths were measured during the summer of 1998 as part of the SHEBA field experiment. Three different water types are identified from the optical properties: 1) very clear surface water within leads, 2) high CDOM, low particle concentration waters, and 3) high CDOM, high particle concentration waters (turbid case). Turbid waters have a high absorption coefficient and are effective in absorbing shortwave radiation near the ocean surface where this heat may be used to melt ice. Nearly 50% more energy from visible light is deposited in the upper 5 m in the turbid water case compared to the clearest natural waters. A simple parameterization of the absorption of shortwave radiation is developed for each water type. Furthermore we suggest how the parameterization may vary as a function of season and location.