For effective support of offshore ice-resistant structures on the north-east Sakhalin shelf during winter season it is necessary to know the variability of ice cover distribution over the water area. Ice cover redistribution followed by formation of ice compression and ice divergence zones over the Sakhalin offshore water area was earlier observed (Kalinin E.N., Truskov P.A., 1996; Kalinin E.N. 1999) as a function of various metocean conditions. Consideration and forecast of ice compression/divergence zones will facilitate efficient planning of vessels operation to support offshore ice-resistant structures. Synchronous observations of ice drift based on three onshore radar stations (RS) (cape Levenstern bay Odoptu, village Komrvo) allow the tracing of ice cover distribution variation under changing metocean conditions in the near-shore zone of the north-east Sakhalin shelf.
The hourly data for March/April/May were reviewed based on three onshore radar stations (c. Levenstern, b.Odoptu, v.Komrvo). The tidal drift was estimated by filtering the resultant ice drift observations with empirical Dudson filter.
The reverse tidal movements of ice are typical for the north-east Sakhalin shelf and their contribution to the resultant ice drift may be as high as 60–80%. Various points of the north-east Sakhalin near-shore zone are not approached by the tidal wave simultaneously. Therefore, tidal ice drift vectors may have different orientations for different water areas of the self (Fig. 1).During a day, tidal ice drift vectors (as well as resultant ice drift vectors) may be directed either toward each other or from each other. The tidal ice drift vector turns clockwise and the principal axis of a scatter ellipsis has a NNW-SSE orientation. The turn of the ice drift vector in b.Odoptu lags 3–4 hours behind that in c.Levenstern water area. Four typical ice drift scenarios may be distinguished under tidal ice drift (Fig. 2).
