Action of cabbeling-anticabbeling effect in formation of the halocline in estuaries on example of the Razdolnaya River (Peter the Great Bay, Japan Sea)

Abstract

Nonlinearity effect of the seawater density equation for mixing of waters with different salinity is considered for a case of the halocline formation in estuaries. Depending on salinity, density of the mixture can be higher (at low salinity) or lower (at high salinity) than the arithmetic mean density of the two components, so an effect of compaction during mixing (cabbeling) is observed in the upper part of halocline with lower salinity, whereas an effect of decompaction during mixing (anticabbeling) occurs in its lower part with higher salinity. The salinity value at the point of cabbeling change to anticabbeling is calculated that depends on average temperature of the mixed waters. In the real halocline (estuary of the Razdolnaya/Suifen River flowing into Peter the Great Bay, Japan Sea), the highest vertical gradient of salinity is observed along the isohaline, which value changes depending on temperature. In summer, when the water temperature in the estuary is about 22 oC, the maximum gradient is observed at the isohaline 10 psu, while in winter, when the temperature drops to 1 oC, the maximum gradient shifts to the isohaline 18 psu. These isohaline values correspond to the salinity values for the point of cabbeling change to anticabbeling. The cabbeling effect above this level promotes sinking of water, but the anticabbeling effect below this level promotes rising of water. This encountering convergent motion is an additional mechanism of the halocline self-sustaining in sharp state.