Observation and modeling of upwelling in the southeastern Baltic

Abstract

The specific features of the upwelling in the southeastern Baltic have been studied by comparing the field observations and numerical simulations. The upwelling registered in October 2005 (when a gale caused by a northeastern wind with a velocity of 15 m/s continued for about three days after a period of relatively calm weather during which the thermohaline structure was in the state close to the summer one) has been considered in detail. The gale caused a decrease in the temperature by approximately 4°C in the along-shore belt with a width of about 8 km in the region with depths of about 25 m located at a distance of approximately 8 km from the shore. The changes in the thermohaline structure that originated as a result of this gale were simulated using a 3D numerical model based on the Princeton Ocean Model (POM). This made it possible not only to consider the variability of the thermohaline fields at the observation region but also to study a rather wide region and to consider the field of velocity in addition to the fields of temperature and salinity. Subsequently, the numerical model made it possible to estimate the upwelling effect during cooling of the upper layer, which was more intense than the effect of turbulent mixing by an order of magnitude. It was confirmed that the specific features of the upwelling spatial structure depend on the geographic position of the upwelling observation region and on the velocity and duration of the wind that causes the upwelling.