WATER EXCHANGE IN THE ESTUARY OF THE RAZDOLNAYA RIVER (AMUR BAY, JAPAN SEA) IN THE ICE COVERED PERIOD

Abstract

Environmental conditions in the Razdolnaya/Suifen Estuary and adjacent marine area were monitored from 2008 to 2018, by seasons, including winter observations in January 2014 and January 2018. The river discharge in winter was low: 6 m3 /s (mean annual discharge is 73 m3 /s). The estuary was covered by ice. The cline of salt water at the bottom was traced upstream up to 28 km from the river mouth. The currents in the estuary changed in tidal cycle. Increasing of salinity and temperature (> 2о ) at the bottom was observed in the distance 20–24 km from the river bar (this area was distinguished by relatively thin ice, 20 cm, against 40–70 cm in the rest of estuary). Modeling of the water balance in the estuary showed an additional source of salt water in the internal estuary, beyond the direct exchange with the sea over the river bar, that was presumably the water flow through the aquifer. This groundwater discharge was responsible for supporting of the salted bottom layer and for temperature and salinity increasing in the internal estuary during the ebb phase in conditions of limited water exchange by two-layered estuarine circulation because of ice cover at the river mouth.