Identification of areas of frequent patch formation from velocity fields

Tracking areas with increased likelihood of surface particle aggregation in the Gulf of Finland: A first look at persistent Lagrangian Coherent Structures (LCS)

“…A partial match (5 out of 8 areas) was found in visually comparing the previously investigated areas of high levels of finite-time compressibility (FTC, prone to accumulation of floating items) in the Gulf of Finland, and regions where the newly calculated mean FTLE values were consistently above threshold, during the years 1987-1991. This partial match further supports the view that the areas identified using the concept of finite-time compressibility (Giudici and Soomere, 2013; display increased clustering potential and represent probably up/downwelling hotspots.…”

“…From this metric produced for the entire Gulf of Finland, and over such a time range, we made an attempt to find areas in the basin, which exhibit consistently high FTLE values, across an entire calendar year. The results were compared with the set of regions, identified in (Giudici and Soomere, 2013), which are characterised by high-FTC values during the same time frame (Figure 4).…”

“…Initial studies on patch generation in the area (Giudici et al, 2012;Giudici and Soomere, 2013;Kalda et al, 2014) were based on the output of a medium-resolution ocean circulation model designed for climate studies (Meier et al, 2003;Meier, 2007), which was only to some extent able to properly resolve eddies and therefore only partially able to represent the dynamics of the area correctly. The velocity fields used in subsequent studies and this paper are obtained by means of the OAAS (Andrejev and Sokolov, 1989;1990) hydrodynamic model, as carried out in the framework of BONUS+ BalticWay cooperation (Soomere et al, 2014), with a spatial resolution of 1 nautical mile (NM).…”

“…This means that each time span should much shorter than this time scale (e.g., ≤3 days) to avoid distortions to the triangular elements by the presence of the shores. Using this technology, nine areas of the GoF were identified, which stably show increased values of FTC compared to the background level (Giudici and Soomere, 2013). These areas might owe their existence to the turbulent interactions between several drivers (Messie and Chavez, 2017;Vucelja et al, 2007;Balk et al, 2004;Denissenko et al, 2006;Martin, 2003;Delpeche-Ellmann et al, 2017).…”