Abstract:

In this paper, the characteristics of the tide in the sea area near the Great Wall Station, Antarctica are analysed by means of hourly water level observations acquired at the Great Wall Station from March 1987 to February 1988. The conclusions are as follows: 1.The tidal waves near the Great Wall Station come mainly from the M component of tide wave systems which rotate clockwise in the South Pacific Ocean and the South Atlantic Ocean. They propagate into the Great Wall Bay through the Bransfield Strait and the Maxwell Bay from northwest and from southwest, respectively. 2.The tide at the Great Wall Station belongs to an irregular semi-diurnal tide. On an average in a year, there are monthly about 21 days when two high and two low tides occur daily; and about 6 days when one high and one low tide occur daily; and the other 4 days lie in the transition state. 3.The daily inequality of tide, mainly the daily inequality of low tide,is obvious. 4.The yearly mean duration of rise is not equal to the yearly mean duration of fall, and the difference between both is 21 min. in the year. The monthly mean durations of rise and fall all have two peaks (in March and October, respectively) and two troughs (in June and December respectively) for that year, which is closely related to the number of days when the diurnal tide occur monthly. 5.During the period of investigation, the yearly mean tidal range was 1.243 m and the maximal tidal range was 2.380 m for that year. The monthly mean tidal range reached the maximum and the monthly maximal tidal range reached the minimum near the vernal and autumnal equinoxes (in March and September) and, conversely, near the summer and the winter solstices (In June and December). 6.During the investigation period, the annual mean water level was 3.235m, the maximum water level, 4.351 m (at 08:28, March 31, 1987) and the minimum water level, 1.654 m(at 14:02, Dec. 22, 1987) for that year. In the winter semi-year, the mean water level was lower (the lowest in August) and its change was larger and in the summer semi-year, it was higher (the highest in November) and had smaller changes.