The freezing of water to the base of the glacier, increasing the mass of the glacier and Antarctic Ice Sheeting its basal temperature if that temperature is below the freezing point. The result of basal accumulation is typically observable in ice cores or at glacier margins as accreted ice that is relatively clear, often with some concentration of dispersed sediments incorporated from the glacier bed during freezing. Accreted ice may also be distinguishable from glacier ice (the latter sometimes referred to as meteoric ice in this context) by differences in isotopic content, geochemical composition and optical properties, and may have distinctive dielectric properties by which it can be recognized in ground-penetrating radar records. Accreted ice at the base of an ice shelf is referred to as marine ice. For purposes of the glaciological method, basal accumulation is indistinguishable from internal accumulation in that both represent addition of mass to the glacier that goes unaccounted for by surface observations.