Recent upward shift of the deep convection system in the Japan Sea, as inferred from the geochemical tracers tritium, oxygen, and nutrients

The thermohaline circulation system in the Japan Sea, an almost land-lock-e d marginal sea in the northwest Pacific, is now in a transition state. Comp arison of vertical profiles of tritium, oxygen and nutrients between 1984 a nd 1998 demonstrates the following Mo points: (1) the supply of dense surfa ce seawater to the bottom layer (>2,500 in in depth) has almost ceased sinc e 1984, and (2) the intrusion of surface seawater to an intermediate depth range (between similar to 700 in and similar to2,000 m in depth) has been r einforced during this 14-year period. Such transitional upward shift of the thermohaline conveyor belt in the Japan Sea is thought to have separated t he bottom water from the conveyor belt and brought about a stagnant mode of the bottom water.