In-situ ice and meteorological observations in the southern Sea of Okhotsk in 2001 winter: ice structure, snow on ice, surface temperature, and optical environments

The 2001-ice season in the Sea of Okhotsk was characterized by extraordinarily developed ice extent. During the period February 17 to 21, we conducted in-situ observations in the southern ice area with the icebreaker 'Soya'. In this paper, we show the observational results, concerning the core sampling of about 1.3 m-thick ice, snow sampling, surface temperature, and solar radiation under clear sky conditions. It is shown that (1) the sampled ice core is composed entirely of granular ice, (2) the 30 cm-thick snow pack overlying sea ice is composed mainly of depth hoar and significant vertical gradients of δ^<18>O and temperature are found within the snow, probably associated with the depth hoar formation, (3) surface temperatures as low as about -30°C are detected on snow-covered sea ice floes at nighttime under almost clear and light breeze conditions, (4) from the estimation of the turbidity coefficient, the atmosphere over the ice-covered area is considered to be significantly clean. Furthermore, the NOAA/AVHRR satellite data are used to estimate the surface temperature distribution in the southern Sea of Okhotsk. It is shown that these data are useful for discriminating thick ice floes.