Forced and self-organized shoreline response for a beach in the southern Baltic Sea determined through singular spectrum analysis

Temporal and spatial variations in shoreline position along the southern Baltic coast were investigated using singular spectrum analysis (SSA) with the overall aim to determine characteristic patterns in the shoreline response and whether these patterns displayed forced or self-organized behavior. The investigated beach is located at Lubiatowo on the Polish Coast and is mildly sloping with multiple bars having a median grain size of 0.22 mm, being typical for the coast in the southern Baltic Sea. Data on coastal morphology have been collected at Lubiatowo including (1) bathymetric surveys since 1987 twice a year to cover changes in the seabed (along 27 lines covering a longshore×cross-shore area of 2600×1000 m), and (2) beach topography surveys since 1983 every 4 weeks on the average, extending from the shoreline to the dune foot (along the same 27 lines). Furthermore, several dedicated field campaigns have been carried out at Lubiatowo, as well as measurements of deep-water wave properties since 1998. SSA was employed to the time series of shoreline position from all 27 survey lines. The analysis method demonstrated a large potential for detecting temporal patterns from fairly short and noisy time series with irregular sampling interval. In summary, three dominant patterns emerged jointly reproducing 70–90% of the overall variation in the data for the different survey lines. These temporal patterns were demonstrated to represent forced and self-organized components describing the variation in shoreline position. The forced components could be related to the mean properties of the wave climate, whereas the self-organized components were mainly influenced by particular events or features of the beach such as storm waves, storm surges, beach type (dune, cliff), and sediment characteristics.