5
Descriptive Oceanography
3. Lithogenous: clay minerals (Al silicates) and quartz (SiO 2 ) as rock fragments transported by wind, rivers, glacial waters, and volcanic sources
4. Cosmogenous: ferric meteorites (Fe 2 O 3 ) from outer space
1.3 Distribution of Temperature and Salinity for Ocean Waters
Much of our descriptive knowledge of the physics of the oceans comes from an examination of the properties of seawater from place to place. Our knowledge of the distribution
of various properties comes from the collection of measurements made at oceanographic
or hydrographic stations. Properties such as temperature, salinity (the grams of sea salt in
1 kg of seawater), and the concentration of oxygen, nutrients, and so on are measured as a
function of depth. These measurements at a given station are plotted as a function of the
depth (which can be related to the pressure, 10 m ~ 1 bar) and are called a vertical profile.
Profiles from a string of stations can be combined to form a vertical section. The common
values of a given property are connected to give a contour of the property of interest as
a function of depth and distance. Similar contours of common properties can be made of
surface waters and waters at a fixed depth (e.g., 4000 m). The contour lines can be used to
elucidate the horizontal and vertical flow of waters from sinking, upwelling, mixing, precipitation, freezing, and so on. The basic assumption is that ocean waters within a given
region have similar average properties over time. The variation with time, or temporal
variability, can be observed from anchor stations, fixed buoys, floating instrument packages, and, for surface waters, from satellites.
The vertical distribution of the density of seawater controls vertical mixing in the
oceans. Since the density of seawater is directly related to the temperature and salinity
of ocean waters, it is useful to examine the typical distributions of these properties. The
distribution of temperatures of ocean waters is zonal, with lines of constant temperature
(isotherms) (see Figure 1.4). Near the western coast of both South America and Africa,
however, the surface waters have lower temperatures because of upwelling. Open ocean
90°E
20
20
15
29
20
25
25
24
15
27
25
25
27
27
0°
20°
40°
60°S
20
20
15
5
10
0
0
28
20
10
10
5
0
–1
15
10 5
0
–1
20
20
27
27
27
25
25
28
15
15
15
13
10
5
10
5
0
–1
Surface
Temperature
February
25
15 20
25
25
25
28
28
28
10
5
5
0
0
60°N
20°
40°
180°
90°W 0°
Figure 1.4
Temperature of ocean surface waters.
Descriptive Oceanography
3. Lithogenous: clay minerals (Al silicates) and quartz (SiO 2 ) as rock fragments transported by wind, rivers, glacial waters, and volcanic sources
4. Cosmogenous: ferric meteorites (Fe 2 O 3 ) from outer space
1.3 Distribution of Temperature and Salinity for Ocean Waters
Much of our descriptive knowledge of the physics of the oceans comes from an examination of the properties of seawater from place to place. Our knowledge of the distribution
of various properties comes from the collection of measurements made at oceanographic
or hydrographic stations. Properties such as temperature, salinity (the grams of sea salt in
1 kg of seawater), and the concentration of oxygen, nutrients, and so on are measured as a
function of depth. These measurements at a given station are plotted as a function of the
depth (which can be related to the pressure, 10 m ~ 1 bar) and are called a vertical profile.
Profiles from a string of stations can be combined to form a vertical section. The common
values of a given property are connected to give a contour of the property of interest as
a function of depth and distance. Similar contours of common properties can be made of
surface waters and waters at a fixed depth (e.g., 4000 m). The contour lines can be used to
elucidate the horizontal and vertical flow of waters from sinking, upwelling, mixing, precipitation, freezing, and so on. The basic assumption is that ocean waters within a given
region have similar average properties over time. The variation with time, or temporal
variability, can be observed from anchor stations, fixed buoys, floating instrument packages, and, for surface waters, from satellites.
The vertical distribution of the density of seawater controls vertical mixing in the
oceans. Since the density of seawater is directly related to the temperature and salinity
of ocean waters, it is useful to examine the typical distributions of these properties. The
distribution of temperatures of ocean waters is zonal, with lines of constant temperature
(isotherms) (see Figure 1.4). Near the western coast of both South America and Africa,
however, the surface waters have lower temperatures because of upwelling. Open ocean
90°E
20
20
15
29
20
25
25
24
15
27
25
25
27
27
0°
20°
40°
60°S
20
20
15
5
10
0
0
28
20
10
10
5
0
–1
15
10 5
0
–1
20
20
27
27
27
25
25
28
15
15
15
13
10
5
10
5
0
–1
Surface
Temperature
February
25
15 20
25
25
25
28
28
28
10
5
5
0
0
60°N
20°
40°
180°
90°W 0°
Figure 1.4
Temperature of ocean surface waters.