Empirical relationship between sea ice thickness and underwater light intensity based on observations near Syowa Station, Antarctica, in austral summer

Abstract

Underwater light intensity was measured as photosynthetically active radiation (PAR) at four sites near Syowa Station, Antarctica, on 30 December 1996, and 3, 11, 17, and 29 January 1997. The sites were covered with several different thicknesses of sea ice (2.06-3.64m) and snow (0.04-0.70m). The estimated PAR intensities just under the sea ice were 0.1-6.6μmolm^-2s^-1. There was a significant negative correlation between sea ice thickness and PAR just under the sea ice. A similar relationship was obtained when the previously reported values in the literature were analyzed. Using data from the present and previous studies, an empirical equation is proposed. The equation implies that snow layer reduces the incidence to about 20% of surface irradiance, and that PAR decreases by one order of magnitude with each 1 m increase of the sea ice thickness.