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Abstract:
The Lagrangian transport of substances is an essential component in understanding the distribution of heat, salt, nutrients etc. in our marine areas As a result this study takes a deeper examination into the contributors of Lagrangian transport in the Gulf of Finland, Baltic Sea by using a synergy of satellite derived sea surface temperature (SST) obtained from EOS, Moderate Resolution Imaging Spectrometer, high resolution bathymetry data and in-situ (surface drifters, wave gauges, meteorological and hydrological measurements) data sources. The experiments of 38 in-situ surface drifters were deployed at different seasons for the period of 2011–2018, and were designed to capture surface drift in uppermost 2 m layer of the sea.
The method examined the relationship of wind and waves on surface drift. Results revealed: (i) Ekman-type drift of surface layer was present in 68% of the occurrences and surface current speed can be expressed as1.5% of the wind speed; (ii) for wave height >0.5 m accounting for higher velocities and (iii) for about 7–14% of the occurrences the surface drift is governed by other processes (e.g. eddies, fronts, upwellings) than direct wind and wave impact. For instance, depending on the stratification and season and bathymetry, the presence of coastal upwellings were identified from satellite based SST, frequently occur during the summer months on time scale of 6‒12 days. As a result surface transport are influenced by a combinations of wind- and wave- during moderate and strong winds but on other occasions also underlying synoptic- and basin-scale circulation patterns.
