The hydrography and ventilation of Kau Bay in Halmahera

Abstract

The hydrography of Kau Bay in Halmahera was studied in 1985 during the Snellius-II Expedition. Contrary to the findings from the Snellius Expedition in 1929–1930 the deep water in the bay was not anoxic although very low oxygen concentrations were encountered in the deepest 30 m of the bay. Rough estimates of the oxygen consumption in the water column and in the sediment indicate that the deep water in the bay is ventilated probably once every year. Within one year the deep water in the bay may become anoxic. This result has been confirmed by estimates of the diffusion time scale of the observed fine structure based on tentative values of the turbulent diffusion coefficient. The flushing appears to be controlled by salinity changes in the surface water of the nearby Pacific Ocean due to shifts of the equatorial current system.