This study addresses the spatial distribution in surface solar flux at conservative scattering wavelengths, in a region where three-dimensional radiative transfer effects are expected to govern the radiation field. Coastal regions at high latitudes offer a unique location to test the results of multidimensional radiative transfer modeling. Near the Antarctic Peninsula, and in similar regions, it has been shown that multiple reflection of photons between a high albedo surface (glacier or snow-covered sea ice) and a cloud layer enhances the downwelling shortwave surface flux by a factor of 2 or more relative to a low albedo surface such as open water [Gardiner, 1987]. Theoretical studies have suggested that photons reflected between a high albedo surface and a cloud should enhance the downwelling shortwave flux not only at the coastal location but also out over the open ocean to a distance of several kilometers [Degünther et al., 1998; Podgorny and Lubin, 1998; Ricchiazzi and Gautier, 1998]. The existence of this phenomenon, which we herein refer to as the “coastal albedo effect,” has been measured under near-ideal conditions by Smolskaia et al.  at Davis Station, Antarctica, using broadband ultraviolet (UV) radiometers mounted on both a sledge to move inland and in a boat to make open water transects perpendicular to the high albedo coastline.
 Here we are interested in the prevalence of this effect at Palmer Station, Antarctica (64° 46′S, 64° 04′W), for two reasons. First, Palmer Station is the central facility for an extensive Long Term Ecological Research (LTER) program [Smith et al., 1995, 1999], in which many of the physical forcing mechanisms acting on the base of the marine food web, primary production by phytoplankton, are monitored. The coastal albedo effect may be important with respect to the light levels experienced by photosynthetic organisms in the upper water column near the coast. To facilitate marine ecological studies involving primary production throughout the Southern Ocean, satellite-based methods have been proposed to map the spatial distribution of Antarctic UV and photosynthetically active radiation (PAR, 400–800 nm), using plane-parallel radiative transfer theory and an independent pixel approximation [Lubin et al., 1994; Nunez et al., 1997; Krotkov et al., 2001]. If the coastal albedo effect prevails throughout the region, some sort of parameterized correction to the independent pixel approximation may be necessary in coastal waters. Second, an empirical determination of the significance of multidimensional radiative transfer effects is of general interest to atmospheric science for validation and refinement of ongoing theoretical work.