Hydrodynamics and Thermohaline Features of Reef Waters
43
Fig. 2.7. TIS curve in surface waters
of the southern GBR; average data in
Sept.-Oct. 1967. (After Brandon
1973)
tOe
30
29
28
27
26
25
24
23
22
21
20
8%0
40 50 60 70 80 90360010 20
evaporation it could increase to as much as 38-40%0, as in the lagoon of the
Canton atoll (Smith and Jokiel 1978). Further increase of salinity in lagoons
of such atolls with a residence time of water of 1-2 years is prevented only
by the water exchange through the porous lime body of the reef (Salvat
1981b; Rougerie 1985). The vertical gradients of salinity in lagoons are
usually very low because of an extensive turbulence. They vary within
0.05-0.2%0 per 50m (Ford 1949). The gradients may increase during the
rainy seasons in their coastal areas, but they are quickly leveled by
turbulence.
Degrees of temperature and salinity variations in reef waters are reflected
well by the TIS curves. One of these for the GBR lagoon is given in Fig. 2.7.
It denomstrates significant fluctuations of e and S even within one region
and during one season. The fluctuations are caused by large diurnal changes
of water temperature in shelf areas as well as by extensive evaporation. The
temperature of shelf water and the thermal stratification are also influenced
in this area by fluctuations of the East Australian current, the barotrophic
oscillations of water level, and also by the variations in the to and S of waters
coming from the ocean into the lagoon (Andrews and Gentien 1982;
Wolanski and Bennett 1983). The scale of fluctuations of the temperature
itself could be large even within the same region (Pickard 1983), and
especially on the high-latitude reefs situated near the boundaries of coral
reef growth (Potts and Swart 1984). For example, on reefs of the Persian
Gulf seasonal temperature of the water varies from 16 to 40°C (Kinsman
1964), at the Abrolhos reefs (S.W. Australia, 28°S) 17 to 28°C, and in the
southern GBR 23°-24°S from 18 to 30°C (Pickard 1983). But in shallows
of the reefs in low latitudes even the diurnal fluctuations of temperature
reach 5-8°C, while in deep lagoons and up the outer slopes they are
negligible. The vertical stratification there is also slight or absent. The
43
Fig. 2.7. TIS curve in surface waters
of the southern GBR; average data in
Sept.-Oct. 1967. (After Brandon
1973)
tOe
30
29
28
27
26
25
24
23
22
21
20
8%0
40 50 60 70 80 90360010 20
evaporation it could increase to as much as 38-40%0, as in the lagoon of the
Canton atoll (Smith and Jokiel 1978). Further increase of salinity in lagoons
of such atolls with a residence time of water of 1-2 years is prevented only
by the water exchange through the porous lime body of the reef (Salvat
1981b; Rougerie 1985). The vertical gradients of salinity in lagoons are
usually very low because of an extensive turbulence. They vary within
0.05-0.2%0 per 50m (Ford 1949). The gradients may increase during the
rainy seasons in their coastal areas, but they are quickly leveled by
turbulence.
Degrees of temperature and salinity variations in reef waters are reflected
well by the TIS curves. One of these for the GBR lagoon is given in Fig. 2.7.
It denomstrates significant fluctuations of e and S even within one region
and during one season. The fluctuations are caused by large diurnal changes
of water temperature in shelf areas as well as by extensive evaporation. The
temperature of shelf water and the thermal stratification are also influenced
in this area by fluctuations of the East Australian current, the barotrophic
oscillations of water level, and also by the variations in the to and S of waters
coming from the ocean into the lagoon (Andrews and Gentien 1982;
Wolanski and Bennett 1983). The scale of fluctuations of the temperature
itself could be large even within the same region (Pickard 1983), and
especially on the high-latitude reefs situated near the boundaries of coral
reef growth (Potts and Swart 1984). For example, on reefs of the Persian
Gulf seasonal temperature of the water varies from 16 to 40°C (Kinsman
1964), at the Abrolhos reefs (S.W. Australia, 28°S) 17 to 28°C, and in the
southern GBR 23°-24°S from 18 to 30°C (Pickard 1983). But in shallows
of the reefs in low latitudes even the diurnal fluctuations of temperature
reach 5-8°C, while in deep lagoons and up the outer slopes they are
negligible. The vertical stratification there is also slight or absent. The