Karadeniz'de deniz seviyesi değişimleri ve kıyı alanları üzerindeki etkileri

Scientific researches assert that global sea level rise will accelerate during the 21st century in response to increasing ocean thermal expansion and glaciers/ice sheet melting. It means that the sea level rise should consider a serious threat especially for the unprotected coastal regions. Lying between Europe and Asia, the Black Sea is one of the most interesting and unique seas. It has three singular characteristics: (1) The Black Sea is the most isolated from the Atlantic Ocean that is connected to this remote ocean via the Marmara, Aegean, and Mediterranean seas through a chain of narrow straits: Bosporus, Dardanelles, and Gibraltar. Nevertheless, the Black Sea is relatively deep for such a sea. (2) The drainage area of the Black Sea containing major European rivers (Danube, Dnieper, Don, etc.) is roughly 5.5 times size of its surface area. (3) And the Black Sea is the world's largest anoxic basin, nearly 90% of its water volume is anoxic. The Black Sea coastal zone has also a densely populated. Therefore, monitoring of sea level change is significant especially in terms of the social-economic activities and ongoing coastal erosion in the region. In this context, this study aims to clarify present-day sea level changes in the Black Sea from different sea level observations. Analysis of multi-mission satellite altimetry data revealed that the sea level in the Black Sea rose at a mean rate of 3.2 ± 0.6 mm/year from January 1993 to December 2014. The results show that maximum sea level occurs in May-June, whereas its minimum occurs during the September-November period. Moreover, the relative sea level at 13 tide-gauge stations along the Black Sea coast generally indicated rising trends. The coastal sea level changes were also investigated by satellite altimetry data; especially for Poti and Tuapse stations having long-term data, the results were consistent with tide-gauges. On the other hand, in order to detect the impact of vertical land motion on the coastal sea level change, the vertical movements at 3 Global Positioning System (GPS) stations (SINP, SLEE and TRBN), which were almost co-located with the Sinop, Sile and Trabzon tide-gauge stations, were analysed using GAMIT/GLOBK software. Consequently, at these 3 stations, the trends of absolute coastal sea level had a better agreement between satellite altimetry and tide-gauge + GPS. For the period of September 1981 – November 2015, it was determined that the Sea Surface Temperature (SST) in the Black Sea rose 0.04 °C per year, and its annual amplitude reached its maximum in August. Until the prior to mid-1999 and after early-2008, good correlations were observed between SST and sea level changes. On the other hand, over the period of 2002–2017, the rate of seawater mass change in the Black Sea from the Gravity Recovery and Climate Experiment (GRACE) mascon solutions was 2.3 ± 1.0 mm/year. Besides, the sum of mass-induced and steric-induced (temperature + salinity) changes showed similar fluctuations with the total sea level changes obtained from altimetry. Furthermore, in this study, vertical land motion along the Black Sea coast was estimated from combination of satellite altimetry and tide-gauge sea level time series. The obtained velocities were compared with the observations of 20 GPS stations in the region, and the results generally exhibited a good agreement.