Possible Presence of Shear Instabilities at Steep Slopes during an Upwelling Event in the Gulf of Finland, Baltic Sea

Abstract

Delpeche-Ellmann, N. and Soomere, T., 2018. Possible Presence of Shear Instabilities at Steep Slopes during an Upwelling Event in the Gulf of Finland, Baltic Sea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 481–485. Coconut Creek (Florida), ISSN 0749-0208.The cooler water jets that are present during wind-induced coastal upwellings are known to become unstable after some time and develop into sub-mesoscale phenomena that contribute to the overall mixing. In this study we examine the possibility of vertical shear instabilities, in particular the Kelvin–Helmholtz instability existing in an area where steep bottom slopes are present during an upwelling event in the Gulf of Finland, Baltic Sea. The study utilizes a combination of in-situ sampling stations, satellite derived sea surface temperature (SST) data and the HIROMB model for the Baltic Sea. Examination of the velocity shear and stratification shows that it is possible for the KHI instabilities to exist most popularly at the thalweg section of the study area at a depth of 10–16 m. It is also at this exact location that the cross-shore jets were found to develop into meanders and filaments and the greatest gradient in the SST were observed. Thus these observations signal the possibility of the KHI developing in the vicinity of steep slopes and contributing to the overall mixing.