The tides of the Ob bay Печать

SERGEY V. KOROTKOV. JSC "AMIGE", Russia

Prior to the beginning of 1990th years in the Ob Bay of the Kara Sea there was well advanced network of sea and estuary weather stations and observational level gauges where regular sea level's observations were carried out.

The next years, in connection with the general crisis which has captured all spheres of a life in the territory of the former USSR, in the specified area there was a sharp reduction of station network. The part of stations has been closed; the part has reduced volumes of sea level observations. Last years, in connection with liquidation of Amderma Department of Hydrometeorology and transfer of its functions to Northern Department of Hydrometeorology (Arkhangelsk), in the Ob and Taz Bays the regular sea level observations at a coastal stations have practically stopped (except for some stations located on the rivers and belonging to Omsk Department of Hydrometeorology).

Prior to the beginning of 1950th years sea level observations at all stations located at the Arctic coast were recorded in relative high system of each station. Then the majority of stations have been converted in the Baltic high system.

The most of sea level stations has observed tides all-year-round. The level station Drovjanoy and Jamsalja observed tides only in the shipping season. The polar stations Tatibjajaha, Sejacha, Antipajuta have been equipped with sea level recorders. The other sea level stations were of pile type with level gauges. The water level observation before 1962 were carried out at random, and then began to be earned out at 3, 9, 15 and 21 hour of Moscow (winter) time.

The data of sea level observations were published in editions of State water cadastre (SWC) from 1936 to 1962 and from 1977 to 1985. For the periods 1963-1976 and 1986-1989 the data of sea level observations have not been issued because of the endings of financing of SWC's jobs.
hi an open part of the Ob Bay the tide's observations are earned out only by JSC "AMIGE" during the shipping season, since 1995 using buoy stations (BS) equipped with the tide gauges WLR-7 and SBE-26-03. For reduction the BS's data to the Baltic high system, on sites of coast of the Ob Bay, close to BS locations, are organized temporary sea level gauge stations of pile type with synchronous hourly measurements of sea level fluctuations.

Tides as the determined part of process of fluctuations of a total level are considered to be most well studied for in practice they are used as chart datum of the tidal seas and water areas of geographical objects belonging to them. Now the most accessible to practical use are data on characteristics of tides in a number of the level stations located along both coast of the Ob Bay (the basic and additional stations), published in modern Tide tables.

At the same time results the analysis of measurements of a level in the area Obsko-Tazovskom, added with the measurements executed by experts of JSC "AMIGE" during engineering - hydrometeorological surveys, have allowed to specify distribution of tidal fluctuations of a level to receive their quantitative ratings and an opportunity of calculation for any time interval in any point of the given area.

As to distribution of tidal fluctuations in the Ob Bay it has been noted that though there is general decrease of their size from north to south, in the area of the cape Kamenny the build up of tidal fluctuation is recorded. Presence of such zone shows resonant interaction of a forward wave coming from the northern part of the Bay with its member reflected from the coast and shallows in the “neck” between the capes Kamenny and Parusny. In the mouth of the Taz Bay amplification of standing fluctuations and mode of their oscillations is marked. This results in reduction of tidal fluctuations of a sea level in the area of cape Trehbugorny and approach at 1.5-3 hours before high water and low water at level stations Hasre, Nalivnoy and in a mouth of the river Hamboljaha, in comparison by similar tides at an entrance to the Ob Bay.

After passing a "neck" between cape Kamenny - cape Parusny the tidal wave again gets forward character. Thus tides naturally decrease, because of dissipation energy of a tidal wave.

As a whole the tidal range into the Ob Bay are most expressed lengthways its western coast; time of passage of a tidal wave from sea edge of the Ob Bay to delta of the Ob river makes 10.5 hour.

ARCTIC SHELF OIL AND GAS CONFERENCE 2004