The age of Yellow River water in the Bohai Sea

Abstract

To quantitatively understand the transport timescales of dissolved material discharged from large rivers into a semienclosed sea, the age of Yellow River water in the Bohai Sea was calculated with the constituent‐oriented age and residence time theory (CART) and particle‐tracking method. Yellow River water has a mean age of 3.0 years for the entire Bohai Sea. The spatial variation of the water age is significant: 1.2 years near the Yellow River estuary but 3.9 years in the Liaodong Bay. However, the temporal variation in water age is insignificant. The water particles released at the river mouth need only several days to reach the estuary area. The great water age (1.2 years) near the Yellow River estuary is caused by the presence of old water particles that initially left this area but returned to this area again. Without the reentry of Yellow River water from the Yellow Sea to the Bohai Sea, the mean age of Yellow River water in the entire Bohai Sea decreases to 1.2 years. Calculations without tidal forcing give a reduction in water age by more than 50%, suggesting that tidal forcing plays the most dominant role in controlling the age of Yellow River water in the Bohai Sea. Calculations without winds give an increase in water age by 20–30%, suggesting that wind forcing is secondary factor to the age of Yellow River water. Changes in discharge of the Yellow River and in thermal stratification have limited influence on the age of Yellow River water.