Hydrographic sections

Figure 13.1 Map of the Atlantic Ocean depicting locations of hydrographic sections contoured for this chapter, as well as the locations of the time series study sites referenced. Map (as well as several figures in this chapter) prepared using Ocean DataView (Schlitzer, 2005).

Steady-state mass and tracer conservation equations for all subdomains formed by the intersecting hydrographic sections (see Figure 3) are written as constraint equations for the unknown h,. For a given domain the conservation equation of tracer C is expressed as... 

Longitudinal profiles in the Atlantic Ocean at about 25°W. (a) Potential temperature (°C), (b) salinity, (o) potential density (0 dbar), (d) potential density (4000 dbar), and (e) dissolved oxygen ( j,mol/kg). Source-. After Talley, L. (1996). Atlantic Ocean Vertical Sections and datasets for selected lines. http /sam.ucsd.edu/vertical.sections/Atlantic.html. Scripps Institute of Oceanography, University of California - San Diego. Data are from WOCE hydrographic program. (See companion website for color version.)... 

Fig. 1 a Location of all shipboard hydrographic observations in the Black Sea. Thick lines the standard sections segments (1-3) discussed in the text. Thin lines depth contours of 20, 50, 100, 200, 300, 500, and 1000 m. b Distribution of the shipboard hydrographic stations over the years... 

The Atlantic basin, particularly the North Atlantic, is the most studied of the global oceans, yet there are several important processes and issues remaining to be addressed. Arguably, the most important issue is the paucity of data from the South Atlantic. There have been excellent expeditionary efforts there (i.e., the WOCE sections and the South Atlantic Ventilation Experiment), so the hydrographic system and the nutrient provinces can now be assessed in greater detail. However there has been little focus on processes of the nitrogen cycle in the basin. 

Latitudinal cross section of the potential temperature and salinity of the Atlantic (A) and Pacific (B) oceans. Different water masses are definable by their characteristic temperature and salinity (Table 1.3). (Plotted by using Ocean Data View and WOCE hydrographic data (Schlitzer, 2001).)... 

The hydrographic and chemical standard parameters under investigation are summarized in Section 3.4. The standard distances of sampling depths are 5 m until 20 m, 10 m until 100 m, 25 m until 200 m, and 50 m below 200 m greatest depth is as near as possible to the bottom. Information on the biological parameters under investigation and their sampl i ng will be found in Chapters 15-17. 

Figure 1. Location of the southeastern Bering Sea, showing hydrographic regimes and bathymetry. Also shown in the position of a vertical section across the region (see Figure 4).

Figure 9 Two deep Pacific zonai sections of He. Data are presented as isotope ratio anomaiy %), reiative to atmospheric heiium. Sampies were processed during the WOCE Pacific hydrographic expeditions from 1989 to 1994.

Figure 7 (A) Map showing iocation of hydrographic stations aiong the southern end of the Kermadec Arc northeast of New Zeaiand. (B) i5( He)% contoured in section view aiong the southern end of the Kermadec Arc, showing He-rich water-coiumn piumes emanating from severai of these subduction zone voicanoes. From de Ronde et ai. (2000).

The section inverse approach developed by Wunsch exploits hydrographic data along sets of oceanographic sections, and allows estimation of absolute flow velocities perpendicular to the sections. The method was later extended to include nutrient and oxygen data allowing to estimate nutrient and oxygen fluxes across the sections. 

For rock or earthfill dams, failure takes a longer period of time than for concrete dams. The time for the total collapse of the structure may range from a few minutes to several hours. The failure of a rockfiU dam may take a considerably longer time than the failure of an earthfill dam. In making erosion calculations to determine the time and rate of failure, an initially breached section or notch should be postulated. These computations should also yield the outflow hydrograph. 

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