Eustatic sea-level rise

In 1923-1985, the Black Sea was characterized by an increase in its water volume, the rate of which attained + 1.5 km3 year 1 [3]. If one converts this value into the sea level change for the same period (with the sea area being 423 x 103 km2), then the rate of the eustatic sea level rise will be 3.5 mm year x. By different assessments, the eustatic (volumetric) increase in the Black Sea level comprises 2.0-4.0 mm year-1 [3,8,24]. 

The rate of the RSLR in the Black Sea and the Sea of Azov and at their river mouths (Table 3) varies over a wide range [3,8,24-26]. These data show that actual eustatic sea level rise increased with time and by the beginning of the 21st century reached in the Black Sea 4 mm year x. Besides, these data confirm the assumption that the land subsidence plays very important role in the RSLR in river mouth areas and can reach 3-6 and even 12 mm year-1. The most values of the RSLR and subsidence are typical of the coastal parts of the Danube and Rioni deltas (Table 4). 

Eustatic sea-level rise, or global changes in the sea level because of changes in the mass of water in oceans, ocean volumes, and temperature changes. 

Accretion balance refers to the net change in sea level relative to marsh surface elevation at a particular site over time. For a coastal wetland to remain at the same elevation over time, accretion must be equal to subsidence plus eustatic sea-level rise. 

According to Equation 14.1, the eustatic sea-level changes as well as the vertical crustal movements. The eustatic change is regarded constant over the whole area. Hupfer et al. (2003) propose a local eustatic rise of l.Omm/year for the last century within the western Baltic Sea. The vertical crustal movements show remarkable differences over the entire Baltic Sea area (Fig. 14.3), reflecting here the glacioisostatic adjustment (GIA). The center of uplift is in the Bothnian Bay, with a rate of about 9 mm/year. The coast of the southern Baltic Sea shows subsidence reflecting compensation currents in the upper mantle. 

With eustatic sea level transgression and flooding of continental lowlands, transport of terrigenous organic matter into the North American basin may have increased. Analyses of Upper Cretaceous sediments from DSDP Site 6O3B, lower continental rise east of Cape Hatteras, indicate that, the organic matter was continentally derived. d C values of -23.5 to 27.1°/oo, C/N ratios of 32 to 72, and lipid class maxima of unbound alkanes (C-. and Cp-), unbound fatty acids (C and C2g) and bound fatty acids (C-g. 

The eustatic rise in the levels of the Black Sea and the Sea of Azov is the consequence of the ocean level rise and the positive water balance of these seas. 

The mechanism of the transfer of the eustatic component of the world ocean level rise into the Black Sea and the Sea of Azov is an intricate and poorly understood process. It is clear that in these seas the eustatic rise differs from that in the ocean as a whole. The main cause is relative isolation of these seas from the ocean. Thus, the volumetric changes in the sea water levels are likely to be more susceptible to changes in the ratio between the components of the water balance of the sea (river runoff, precipitation, and evaporation) than to the eustatic rise in the ocean level. 

The above data evidence that in the 20th century the eustatic rise in the Black Sea level markedly exceeded the eustatic rise of the level in the Atlantic Ocean (1.7 mm year-1 [23]) and in the Mediterranean Sea (1.1-1.3 mm year 1 [3]). In most publications, the rise in the Black Sea level is explained by some specific features of its water balance in this period an increased river water runoff into the sea (first of all, that of the Danube River), abundant precipitation over the Black Sea s water surface, and decreased evaporation. 

It is impossible to accurately assess the contribution of the subsidence of deltaic deposits to the RSLR, because the amount of subsidence greatly varies (both in space and time) within the same delta. The only way to assess this contribution is to compare the actual level rise (RSLR) with the average rates of the eustatic level rise of the sea. 

Gronlie, A., 1981. The late and postglacial isostatic rebound, the eustatic rise of the sea level and the uncompensated depression in the area of the Blue Road Geotraverse. Earth Evolution Science, 1, 50-57. 

---