Event Summary and Aim

The aim of this year's field event (K132) was to measure the visible and UV light field in and under sea ice and the accompanying seasonal changes as the structure of the ice changes. This was an extension of work carried out during the 1965/86 and 1986/87 seasons in which we were able to characterise the visible light field and observed for the first time that the transmission of light by sea ice decreased as the season progressed. This was found to be associated with increasing turbidity of the ice as brine drained from the surface because of the summer warming. The significant result for 1989/90 is that we have extended the measurement technique into the UV and have confirmed that the same results apply in this spectral range. In particular, we have observed that because of the coincidence of the ozone hole and the period of high UV transparency of sea ice, there is a ten-fold increase in total yearly UV dose for organisms living under sea ice.