2
G. DIETRICH:
(WYRTKI, 1971); both had to contend with the inhomogeneity of the observations. Even
with this material many problems could be solved, but numerous other questions await
future work.
The following remarks are restricted to the main facts which make the environmental
conditions of the Indian Ocean different from the other oceans. The new contour map
(DIETRICH and ULRICH, 1968) confirmed many well-known features in the bottom topography: the system of ridges and basins as well as the relative paucity of shallow water
areas. It also shows some of the features discovereq during the IIOE, namely the Eastern
Indian Ridge with a length of 4800 km, and the fracture zones and seamounts. Many
~yw~~~~~~~--~--~~~~ r~~~Tr~rL~~~~~~--~~ O
m
100
100
200
300
30·
N
28·
100
200
O2% Sal.
300
o km
Fig. 1. Longitudinal section of temperature (in 0 C), salinity (in $%0) and oxygen (in % saturation)
in the Persian Gulf. (After KOSKE, 1972 and RABSCH, 1972). The map shows the contour lines (in m)
and the positions of the stations used in the sections. Note the change of depth scale below 100 m
special features are not included in the atlas, e.g. canyons, fans, oil and gas reservoirs on
the Indian shelf. The geophysical measurements concentrating especially on the magnetic
field showed the spreading of the ocean floor and even gave data for the rate of spreading.
This amounts to 2 cm year- 1 and implies that the Indian Ocean is about 10 8 years old.
The contour maps demonstrate a very simple fact, if we look at the situation of the
ocean, relative to the Equator. This is the asymmetric shape imposed by the existence of
the Asian continent. It has two main consequences: first, the ocean is separated from
deep-reaching vertical convection areas in the northern hemisphere; second, the Asian
continent is large enough to develop its own far-reaching atmospheric circulation which
influences the ocean down to 10° S and is known as the monsoon circulation.
The first condition means that it is only in the higher southern latitudes, in the
G. DIETRICH:
(WYRTKI, 1971); both had to contend with the inhomogeneity of the observations. Even
with this material many problems could be solved, but numerous other questions await
future work.
The following remarks are restricted to the main facts which make the environmental
conditions of the Indian Ocean different from the other oceans. The new contour map
(DIETRICH and ULRICH, 1968) confirmed many well-known features in the bottom topography: the system of ridges and basins as well as the relative paucity of shallow water
areas. It also shows some of the features discovereq during the IIOE, namely the Eastern
Indian Ridge with a length of 4800 km, and the fracture zones and seamounts. Many
~yw~~~~~~~--~--~~~~ r~~~Tr~rL~~~~~~--~~ O
m
100
100
200
300
30·
N
28·
100
200
O2% Sal.
300
o km
Fig. 1. Longitudinal section of temperature (in 0 C), salinity (in $%0) and oxygen (in % saturation)
in the Persian Gulf. (After KOSKE, 1972 and RABSCH, 1972). The map shows the contour lines (in m)
and the positions of the stations used in the sections. Note the change of depth scale below 100 m
special features are not included in the atlas, e.g. canyons, fans, oil and gas reservoirs on
the Indian shelf. The geophysical measurements concentrating especially on the magnetic
field showed the spreading of the ocean floor and even gave data for the rate of spreading.
This amounts to 2 cm year- 1 and implies that the Indian Ocean is about 10 8 years old.
The contour maps demonstrate a very simple fact, if we look at the situation of the
ocean, relative to the Equator. This is the asymmetric shape imposed by the existence of
the Asian continent. It has two main consequences: first, the ocean is separated from
deep-reaching vertical convection areas in the northern hemisphere; second, the Asian
continent is large enough to develop its own far-reaching atmospheric circulation which
influences the ocean down to 10° S and is known as the monsoon circulation.
The first condition means that it is only in the higher southern latitudes, in the