Clean Ships, Clean Ports, Clean Oceans: Controlling Garbage and Plastic Wastes at Sea (1995)
Chapter: Red Sea
flow into the Arabian Sea (Pickard and Emery, 1990). Because the Persian Gulf is so shallow, it experiences uniformly high levels of salinity (40-70 psu) and wide seasonal changes in sea temperatures (15-38°c). Thorough wind-driven mixing occurs throughout most of the year (International Maritime Organization, 1994).
The Persian Gulf experiences high evaporation and low rainfall rates—a contributing factor to the high salinity of the water. These factors work to restrict biological diversity, and many species live at or near their limits of environmental tolerance (International Maritime Organization, 1994). Under these conditions, any added stress, such as an oil spill or other pollution event, can disproportionately influence the area.
Red Sea
The Red Sea is a rift valley, resulting from the separation Of Africa and the Arabian peninsula (Pickard and Emery, 1990). With the exception of the Suez Canal, it is closed to the north. It opens to the Gulf of Aden, Arabian Sea, and the Indian Ocean to the south, through the narrow strait of the Bah al Mandab. There is a sill of about 110 m at the Bah al Mandab (Pickard and Emery, 1990).
There are no rivers flowing into the Sea. Evaporation is high (about 200 cm per year), while precipitation averages about 7 cm per year, making this the most saline large body of ocean water in the world (Pickard and Emery, 1990).
The surface layer is saturated with dissolved oxygen; however, absolute values are low (less than 4 milliliters per liter) due to high temperatures and salinities. Red Sea circulation varies seasonally with the winds. In summer (southwest monsoon) the winds are to the south. Surface flow is southward, with outflow through the Bah al Mandab; additionally, there is a subsurface inflow to the north through that strait. In winter (northeast monsoon) the winds over the southern half of the sea change to the north, and there is a northward surface flow over the entire Red Sea, with a subsurface southward flow through the Bah al Mandab. The outflow is from an intermediate layer to about 100 m. This water can be traced through the Arabian Sea and down the west side of the Indian Ocean (Pickard and Emery, 1990).
Residence time for the surface layer has been estimated at six years; for the deep water, about 200 years (Pickard and Emery, 1990). A notable feature of the Red Sea are the hot brine pools found in some of the deepest parts. Pickard and Emery offer the explanation with fewest arguments. They assert that ''this is interstitial water from sediments, or solutions in water of crystallization from solid materials in the sea bottom, released from heating from below and forced out through cracks into the deep basins of the Red Sea.''
TABLE E-1 General Physical Characteristics of MARPOL Special Areas
|
|
depth (m) |
mean area (106km2) |
volume (103km3 |
surface temp. range (°C) |
surface salinity range (psu) |
relative surface water viscositya (%) |
residence time (years) |
|
Antarctic Ocean |
4,000 |
|
|
-2/+4 |
34.6 |
94-110 |
100 |
|
Baltic Sea |
86 |
0.39 |
33 |
-2/+15 |
6-8 |
65-107 |
short |
|
Black Sea |
1,166 |
0.46 |
537 |
9-5** |
18-21** |
53-79 |
2500*-3000§ |
|
Caribbean Sea |
2,491 |
2.8 |
6,860 |
25-28 |
36 |
51-55 |
|
|
Gulf of Mexico |
1,512 |
1.5 |
2,332 |
20-29 |
36 |
50-61 |
100* |
|
Mediterranean Sea |
1,494 |
2.5 |
3,758 |
13-26 |
37-39 |
54-73 |
70-100 |
|
North Sea |
91 |
0.60 |
55 |
5-16 |
34-35 |
67-92 |
0.9|| |
|
Persian Gulf |
25* |
0.24 |
10 |
10-25 |
38 |
55-78 |
long |
|
Red Sea |
558 |
0.45 |
251 |
18-32 |
40-41 |
47-65 |
6.0§ |
|
a Assumes 100% at 0 psu and 0°C. Sources: van der Leeden et al., 1990; *Geyer, 1981; *Sverdrup et al., 1942; **Pinet, 1992; §Pickard and Emery, 1990; ||Otto, 1983 |
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