Bottom topography

Fig. 2.2 Vertical z-levels with partial cells in the bottom level. Bottom topography is shown for arbitrary coarse and high horizontal resolutions...

Abyssal clays are found in greater abundance on the western side of the Atlantic Ocean than on the eastern side. This is due to bottom topography that restricts the flow of North Atlantic Deep Water and Antarctic Bottom Water to the western side of the basin. The lower temperature of the western waters causes the CCD to be somewhat shaUower than on the east side of the basin as calcite solubility increases with decreasing... 

In the bottom topography of the sea, one can clearly distinguish three principal structures the shelf, the continental slope, and the deep-water basin. The shelf occupies up to 25% of the total area of the seafloor and, on average, is restricted to sea depths of 100-200 m. It reaches its greatest width (more than 200 km) in the northwestern part of the sea, which is entirely located within the shelf zone. Almost over the entire extension of the eastern and southern coasts of the sea, the shelf is very narrow (only a few kilometers wide) in the western part of the sea, it is wider (a few tens of kilometers). 

Abstract This chapter is devoted to a description of the present-day bottom topography and types of coasts of the Black Sea, as well as to the general character of the bottom sediments. Two maps of topography and sediments illustrate the morphology of the Black Sea basin and the particular features of the evolution of its coasts. 

The Crimean shelf extends from Cape Khersones in the west to Cape Meganom in the east. It is widest off Cape Sarych (35-40 km) and narrowest off Cape Ayu Dag (5 km) [1,2]. This region is subjected to intensive wave action because it is exposed to all the southerly winds. The boundary of the underwater coastal slope is located at depths of 30-40 m. The near-shore zone is the area of alongshore sediment transport and smoothing of the bottom topography. Underwater and dried abrasive remnants are common the largest of them are confined to the capes composed of strong volcanic rocks [7,8]. 

The eddies were formed off the eastern coast of the Black Sea and moved westward showing a decrease in the phase velocity in the narrowest area of the sea south of the Crimea. In the model version with a flat abyssal floor at a depth of 1540 m, the wavelength comprised 250 km in the east and 190 km in the west with a period of 160 days and a phase velocity of - 2.0-2.5kmday-1. The orbital velocities in the eddies in the surface layer reached 0.45 ms 1 and deeper decreased down to 0.25 ms-1 a depth of 70m and to 0.05 - 0.10 m s 1 at a depth of 1100 m. The wave regime was more intensive in the eastern part of the Black Sea in its western part, eddies dissipated above the continental slope and partially reflected from the western coast. In the study [50], the introduction of the abyssal bottom topography increased (reduced) the sizes and intensities of cyclonic (anticyclonic) eddies by a factor of 1.5-2. The cyclonic (anticyclonic) eddies became more alike the SBCGs (NSAEs) in Fig. 1. The period of the eddies grew up to almost two years, while their phase velocity decreased down to 0.4-0.5 km day-1. 

The authors of [50] regarded the eddies as manifestations of Rossby waves modified by the bottom topography. The parameters of similar waves obtained from the data of altimeter observations (see Sect. 2.4), except for the period, are close to the model values. The annual wave period, which prevails in the observations, is absent in the model this is related to the forcing of the model BSGC by a constant mean annual wind field. 

An analysis of the conditions that accompany the formation of the above-considered deep-sea anticyclonic eddies in the eastern part of the sea observed in 1984,1993,1997,1998, and 1999 allows us to suggest that the factors favoring their generation are the wind forcing and the particular features of the coastline/bottom topography. Correspondingly, the seasonal and interannual differences in intensity of the formation of these kinds of mesoscale anticyclones in the Black Sea are related to the variability in the RC intensity, which, in its turn, is controlled by the intensity of the wind forcing. 

Figur 33 1 Physical and biological upwelling response simulated by the Wroblewski (1977) 2-dimensional coastal upwelling model (A) The circulation in the transverse plane normal to the coast, the bottom topography, and the wind stress. The maximum u and w velocities in the field are —2.9 cm s and 1.4 x 10 cm s , respectively. (B) The daily gross primary production of the water column. (C) The distribution of phytoplankton. Contour intervals are 1 jimol N 1. Redrawn with permission from Wroblewski (1977).

This book explicitly supports an open data policy for the Baltic Sea region, in particular by its Digital Supplement CD with a large number of key parameters provided as long-term series, together with reference data, such as shorelines, bottom topography, or the equations... 

---