Tides occur mainly at diurnal and semidiurnal periods. Tides are semidiurnal with the average height of . Tides&colon; Tanggu has a mixed semidiurnal tide. Tides are semidiurnal, i.e. rise twice a day. Semidiurnal tides in the Kola Bay are about 0.3 metres. The tides are semidiurnal reaching up to . Mixed semidiurnal tides are the norm throughout most of the Gulf. Semidiurnal tides in the Murmansk Fjord are as high as 4 metres. Semidiurnal tides cause reverse currents on the lower of the slough. Atmospheric pressure shows a diurnal or semidiurnal (twice-daily) cycle caused by global atmospheric tides. The Kelvin tide of the Atlantic Ocean is a semidiurnal wave that travels northward. The principal lunar semidiurnal constituent is known as M2 and generally has the largest amplitudes. The tides are semidiurnal, with an average height of and the maximum of . Tides are semidiurnal, with the amplitude of 1.3 meters (4 ft 4 in).