Gulf of California — Roden 
33 
between the temperature-salinity relationships 
for either water mass (Fig. 9). Points for the 
Gulf were obtained from the "E. W. Scripps” 
expedition in 1939 (Sverdrup and staff, 1943). 
The solid curves represent the limits for 
typical Gulf water, the dashed curves show 
the limits for the equatorial Pacific (Sverdrup 
etal. y 1942: 741). 
It is seen that a nearly straight line relation- 
ship exists between the points 16°C., 35.2 / oo 
and 9°C., 34.6 0 / 00 . The salinity minimum lies 
in both cases between 34.5 and 34.6%o and 
has a corresponding temperature of between 
5°C. and 7°C. 
The circulation in the Gulf is rather com- 
plicated and not fully understood. In winter 
(Fig. 10) outflow takes place at the surface 
and inflow at greater depths, in summer (Fig. 
11) the situation is reversed. Thorade (1909) 
mentioned one case of oppositely running 
currents at the surface and at 40 m. near the 
coast of central Baja California. 
In the northern part of the Gulf cooling of 
high saline water in winter leads to the forma- 
tion of a bottom water mass (Sverdrup, 1941), 
which is characterized by a temperature above 
10°C. and a salinity above 34.9°/oo and a 
relatively high oxygen content. This water 
fills the isolated basins of the northern shelf 
and moves southward along the coast of Baja 
California (Fig. 19). 
Tidal currents are strong in the northern 
third of the Gulf and may obtain velocities 
of several knots in the narrows between the 
islands and near the mouth of Rio Colorado. 
The exchange between the Gulf and the 
Pacific Ocean cannot be calculated accurately 
from the available data. It is, however, possi- 
ble to get a rough estimate of the exchange 
of water and salt across latitude 23°N assum- 
ing conservation of these properties. If E 
denotes the rate of evaporation and if Si, So 
and Qi, Qo represent the salinity and amount 
of the in- and outflowing water, respectively, 
the following equations hold (Sverdrup et al ., 
1942: 148) 
So Sj 
Qi = - E Qo = E. 
So - Si So - Si 
Taking E as 1.7 X 10 4 m 3 /sec (see above), Si 
as 34.6 j oo and So as 35. 1 /oo one gets: 
Qi = 1.19 X 10 6 (m 3 /sec) 
Qo = 1.17 X 10 6 (m 3 / sec) . 
It is seen that evaporation plays only a 
negligible part in the general circulation of 
the Gulf, and that inflow very nearly balances 
outflow. If one assumes that the outflowing 
Fig. 9. Temperature-salinity diagram for the Gulf (solid lines) and for the equatorial Pacific (dashed lines). 
