Changes in coastal lithodynamical processes of semi-enclosed seas under changing climate: the case of Lithuania

The Lithuanian coast of the Baltic Sea proper represents a generic type of almost straight, relatively high-energy, actively developing coasts that (i) contain a large amount of finer, mobile sediment, (ii) are open to predominating wind and wave directions, and (iii) are exposed to waves from wide range of directions. The specific two-peak directional structure of predominant winds has created a subtle balance of lithodynamical processes at the Lithuanian coast. This balance has changed during the last 50 years. The shore is more actively eroded now. This leads to the deterioration of recreational space and endangers different coastal engineering structures and other infrastructure objects in the coastal zone.

This work aims to establish the main features of local climate change that may have affected lithodynamical processes at the Lithuanian coast. Geological evidence shows that the largest coastal sedimentary feature in the region, almost 100 km long Curonian Spit, has been stable over several millennia. Therefore, the wave climate has been statistically stationary over long time periods. We present evidence of changes in the directional structure of winds and waves over the last 50 years 1950–2019 that may lead to the loss of stability of several sections of the Lithuanian shore. Such changes have led to substantial changes in the directional structure of the wave approach directions and have caused major shifts in structural features (such as the distribution of accumulation and erosion areas) of the sediment transport at the south-eastern coast of the Baltic proper. Field observations and surveys of different geomorphic features suggest that strong waves approaching from the south-west direction are now the major driver for the coastal processes and cause predominant sediment transport along the Lithuanian coast from the south to north.