temperature, great range of precipitation, and
generally counterclockwise surface circulation.
All are characterized by excess of evaporation
over precipitation; making them highly saline
(see Fig. 2.5, p. 13).
3.2.4 650 Jet Stream Division
Along the west sides of the oceans in low
latitudes, the equatorial current turns poleward,
forming a warm current paralleling the coast,
indicated by the symbol F in the Dietrich system.
These discharge currents are known as the Gulf
Stream and Kuroshio in the Northern Hemisphere, and as the Brazil Current, East Austral
Current, and Agulhas Current in the Southern
Hemisphere. They bring higher than average
temperatures along these coasts. The high velocity of these currents tends to cause a cross circulation. At the left side of the Gulf Stream, for
example, the cross circulation brings water rich
in nutrients from deeper layers to subsurface
layers. This is associated with an abundance of
plankton, causing the greenish-blue color of this
adjacent water.
3.2.5 660 Poleward Monsoon Division
Dietrich classified the poleward monsoon waters
as Mp. These regions occur mainly in eastAsiatic waters, where regular changes in the
direction of the monsoon winds in spring and
fall cause a reversal of the surface currents. The
season of the winter monsoon lasts from November to March. During this time, under the influence of cooling, a strong atmospheric high
develops over Asia. The air in the lowest layers
flows out over the east-Asiatic marginal seas (i.
e., the Sea of Japan, the Sea of Ochotsk, and the
Bering Sea) from north to northwest. During the
summer, from May to September, the flows are
reversed on shore toward the continent.
The off-shore winds of the winter monsoon
carry cold continental air over the seas, whereas
the on-shore winds of the summer bring warm,
oceanic air masses into these regions. Due to
these atmospheric influences, the sea surface
temperatures have the greatest annual variations
found in any ocean. In North Korean and
Manchurian waters, variations of over 20
C,
sometimes even 25
C are found.
In winter the water temperature drops to the
freezing point. Even Vladivostok, Russia, on the
latitude of Florence, Italy, does not remain ice
free. In spring and summer, when the maritime
air masses saturated with water vapor arrive
monsoon-like over these cold oceanic areas, persistent sea fogs develop.
Comparative low salinities are caused by
heavy runoff from the land, great excesses of
precipitation over evaporation, and inflow of
low-salinity, polar continental waters.
3.3
700 Tropical Domain
This is characterized by ocean water that is generally blue, high in temperature, high in salt
content, and low in organic forms. It is divided
into (a) tropical monsoon with regular reversal of
the current system (connected with small annual
variations in surface temperature); (b) high salinity, tropical monsoon with alternating currents;
(c) poleward trades with a strong velocity
directed toward the poles; (d) trade winds with
current moving toward the west; (e) equatorward
trades with a strong velocity directed toward the
equator, and where currents tend to swing offshore and cold water well up from below; and (f)
equatorial countercurrents where currents are
directed at times or during the entire year toward
the east. The global extent of the tropical
ecoregions of the oceans is presented in Fig. 3.4.
3.3.1 710 Tropical Monsoon Division
Located over the North Indian Ocean and the
waters around southeast Asia, is a region affected
by monsoonal winds, which Dietrich designates
as Mt. In winter, the winds blow from the north
and northeast. In this season, the hydrologic
conditions resemble those of a region of trade
wind currents. The surface water flows toward
3.3 700 Tropical Domain
21
generally counterclockwise surface circulation.
All are characterized by excess of evaporation
over precipitation; making them highly saline
(see Fig. 2.5, p. 13).
3.2.4 650 Jet Stream Division
Along the west sides of the oceans in low
latitudes, the equatorial current turns poleward,
forming a warm current paralleling the coast,
indicated by the symbol F in the Dietrich system.
These discharge currents are known as the Gulf
Stream and Kuroshio in the Northern Hemisphere, and as the Brazil Current, East Austral
Current, and Agulhas Current in the Southern
Hemisphere. They bring higher than average
temperatures along these coasts. The high velocity of these currents tends to cause a cross circulation. At the left side of the Gulf Stream, for
example, the cross circulation brings water rich
in nutrients from deeper layers to subsurface
layers. This is associated with an abundance of
plankton, causing the greenish-blue color of this
adjacent water.
3.2.5 660 Poleward Monsoon Division
Dietrich classified the poleward monsoon waters
as Mp. These regions occur mainly in eastAsiatic waters, where regular changes in the
direction of the monsoon winds in spring and
fall cause a reversal of the surface currents. The
season of the winter monsoon lasts from November to March. During this time, under the influence of cooling, a strong atmospheric high
develops over Asia. The air in the lowest layers
flows out over the east-Asiatic marginal seas (i.
e., the Sea of Japan, the Sea of Ochotsk, and the
Bering Sea) from north to northwest. During the
summer, from May to September, the flows are
reversed on shore toward the continent.
The off-shore winds of the winter monsoon
carry cold continental air over the seas, whereas
the on-shore winds of the summer bring warm,
oceanic air masses into these regions. Due to
these atmospheric influences, the sea surface
temperatures have the greatest annual variations
found in any ocean. In North Korean and
Manchurian waters, variations of over 20
C,
sometimes even 25
C are found.
In winter the water temperature drops to the
freezing point. Even Vladivostok, Russia, on the
latitude of Florence, Italy, does not remain ice
free. In spring and summer, when the maritime
air masses saturated with water vapor arrive
monsoon-like over these cold oceanic areas, persistent sea fogs develop.
Comparative low salinities are caused by
heavy runoff from the land, great excesses of
precipitation over evaporation, and inflow of
low-salinity, polar continental waters.
3.3
700 Tropical Domain
This is characterized by ocean water that is generally blue, high in temperature, high in salt
content, and low in organic forms. It is divided
into (a) tropical monsoon with regular reversal of
the current system (connected with small annual
variations in surface temperature); (b) high salinity, tropical monsoon with alternating currents;
(c) poleward trades with a strong velocity
directed toward the poles; (d) trade winds with
current moving toward the west; (e) equatorward
trades with a strong velocity directed toward the
equator, and where currents tend to swing offshore and cold water well up from below; and (f)
equatorial countercurrents where currents are
directed at times or during the entire year toward
the east. The global extent of the tropical
ecoregions of the oceans is presented in Fig. 3.4.
3.3.1 710 Tropical Monsoon Division
Located over the North Indian Ocean and the
waters around southeast Asia, is a region affected
by monsoonal winds, which Dietrich designates
as Mt. In winter, the winds blow from the north
and northeast. In this season, the hydrologic
conditions resemble those of a region of trade
wind currents. The surface water flows toward
3.3 700 Tropical Domain
21