Transcript Document

Advanced Oceanography
Ocean Circulation - Chapter 1
A Review
Circulation in both the oceans and the atmosphere is
driven by energy from the Sun and modified by the Earth’s
Rotation
The oceans are mechanically driven by the atmosphere –
winds. The oceans are thermally driven by the atmosphere
by inducing changes in temperature and salinity
(precipitation and evaporation, review latent and sensible
heat fluxes)
Ocean current system involves
both wind driven surface
currents and density-driven
(thermohaline) deep
circulation.
Look at the winds:
Wind bands – Three convection cells
in each hemisphere
Trade winds = NE (30°N to 0°)
and SE (30°S to 0°)
Westerlies = 60°N to 30°N
and 60°S to 30°S
Polar easterlies = 90°N to
60°N and 90°S to 60°S
Low pressure at 0°, 60°N, and
60°S
Low pressure, ascending air,
clouds, increased precipitation
High pressure at 30°N, 30°S,
90°N, and 90°S
High pressure, descending air,
clear skies, low precipitation
Now look at the currents:
Review the Coriolis Force
Air and water masses
moving over the surface
of the Earth are subject
to the Coriolis force.
The Coriolis force acts
at right angles to the
direction of motion, is
zero at the Equator and
increases to a maximum
at the poles.
Review The Radiation Balance
The radiation
balance of the
Earth-oceanatmosphere
system is
positive at low
latitudes and
negative at high
latitudes.
Poleward Heat Transport: Upper Atm.
Wind systems in the
atmosphere and
current systems in the
ocean redistribute this
heat around the
planet.
Sea-surface
temperatures
during
Northern
Hemisphere
summer
Sea-surface
average
salinities in
parts per
thousand
(‰).
Fig. 6-16, p. 168
North
Temperature
Equator
Latitude
Tropic of Cancer
Tropic of
Cancer
Equator
Tropic of
Capricorn
South
Tropic of Capricorn
Salinity
Temperature
Salinity