4
DYNAMICAL OCEANOGRAPHY
Physical oceanography is the study of the physics of the oceans and seas
and is thus part of geophysics. Other oceanographic disciplines are biological oceanography and chemical oceanography. Over the last decades,
physical oceanography has developed from a descriptive to an explanatory
and predictive science and has matured within the field of environmental
physics. In section 1.1, a brief description is given of the bathymetry of
the ocean basins. Some historical notes on the exploration of the oceans
are provided in section 1.2. In section 1.3, an introduction is given into
the properties of seawater with focus on the concepts of static stability,
potential temperature and the T -S diagram. Furthermore, a first peak of
the global sea surface temperature and sea surface salinity distributions is
given.
1.1. The ocean basins
The Earth is a spheroid, i.e., a sphere that is flattened somewhat near
the poles compared to the equator, due to the action of the centrifugal
force. Some characteristics of the Earth which are relevant for physical
oceanography are provided in Table 1.1. At the moment there are accurate data sets of the surface relief of the Earth. An important data set
is the ETOPO bathymetry, which is available now at 2 ′ resolution (see
http://www.gfdl.noaa.gov/products/vis/data/datasets/etopo2 topography.html). In
Fig. 1.1, a plot of the 5 ′ data set (ETOPO5) is provided using plotting software
from http://iridl.ldeo.columbia.edu/. The global ocean consists of three interconnected basins: the Pacific Ocean, the Atlantic Ocean and the Indian Ocean. The
largest connection between the basins is in the Southern Hemisphere; part of this
connection is unblocked by continents. A much smaller connection between the
Pacific and the Indian Ocean exists through the Indonesian Straits. A connection also exists in the Northern Hemisphere between the Pacific and the Atlantic
through the shallow Bering Strait.
A typical ocean basin starts from the coast, with the continental margin extending to a depth of about 200 m. In width, this margin can vary between several
tens to hundreds of kilometers. Further from the coast there is usually an abrupt
transition from the continental margin to the continental slope, the latter with a
slope of about 5 to 10%. The continental slope connects to the deep basin which
has a typical slope of 0.01 to 0.1%. The deep sea plains are sometimes intersected
by undersea mountain ridges, such as the Mid-Atlantic ridge, and deep trenches,
such as the Marianas trench near the Philippines.
The majority of the surface of the Earth (70.8%) is covered by ocean water
(361×10 6 km 2 ) The volume of land that extends above sea level is about 10 8 km 3
DYNAMICAL OCEANOGRAPHY
Physical oceanography is the study of the physics of the oceans and seas
and is thus part of geophysics. Other oceanographic disciplines are biological oceanography and chemical oceanography. Over the last decades,
physical oceanography has developed from a descriptive to an explanatory
and predictive science and has matured within the field of environmental
physics. In section 1.1, a brief description is given of the bathymetry of
the ocean basins. Some historical notes on the exploration of the oceans
are provided in section 1.2. In section 1.3, an introduction is given into
the properties of seawater with focus on the concepts of static stability,
potential temperature and the T -S diagram. Furthermore, a first peak of
the global sea surface temperature and sea surface salinity distributions is
given.
1.1. The ocean basins
The Earth is a spheroid, i.e., a sphere that is flattened somewhat near
the poles compared to the equator, due to the action of the centrifugal
force. Some characteristics of the Earth which are relevant for physical
oceanography are provided in Table 1.1. At the moment there are accurate data sets of the surface relief of the Earth. An important data set
is the ETOPO bathymetry, which is available now at 2 ′ resolution (see
http://www.gfdl.noaa.gov/products/vis/data/datasets/etopo2 topography.html). In
Fig. 1.1, a plot of the 5 ′ data set (ETOPO5) is provided using plotting software
from http://iridl.ldeo.columbia.edu/. The global ocean consists of three interconnected basins: the Pacific Ocean, the Atlantic Ocean and the Indian Ocean. The
largest connection between the basins is in the Southern Hemisphere; part of this
connection is unblocked by continents. A much smaller connection between the
Pacific and the Indian Ocean exists through the Indonesian Straits. A connection also exists in the Northern Hemisphere between the Pacific and the Atlantic
through the shallow Bering Strait.
A typical ocean basin starts from the coast, with the continental margin extending to a depth of about 200 m. In width, this margin can vary between several
tens to hundreds of kilometers. Further from the coast there is usually an abrupt
transition from the continental margin to the continental slope, the latter with a
slope of about 5 to 10%. The continental slope connects to the deep basin which
has a typical slope of 0.01 to 0.1%. The deep sea plains are sometimes intersected
by undersea mountain ridges, such as the Mid-Atlantic ridge, and deep trenches,
such as the Marianas trench near the Philippines.
The majority of the surface of the Earth (70.8%) is covered by ocean water
(361×10 6 km 2 ) The volume of land that extends above sea level is about 10 8 km 3