150
The Last Resource
oxygen content; but plotting their ow still presents some formidable
problems.
The movement of water polewards from the equatorial regions is
not a simple convection system with warm water spreading north
and south from the equator, sinking at the poles and returning once
more to the equator as bottom water. Nevertheless the Sun’s heat
still plays a prominent part in ocean circulation. Cold currents, such
as the Peru, Benguela and West Australian Currents in the south
and the Oya Shio, Labrador and East Greenland Currents in the
north, move towards the equator to join in the gyres of water warmed
by the greater solar heating in the tropics. At the same time warm
currents, such as the Gulf Stream and the Kuro Shio in the north
and the Agulhas, Brazil and East Australian Currents in the south,
move towards the poles. In this way heat received from the Sun as
well as that permeating through the ocean oor from inside the
Earth is distributed over the planet.
If the Earth lived up to its name and had considerably more land
than oceans, it would be an unbearable place with temperatures
soaring during the day and dropping rapidly at night. The oceans
can act as a global thermostat as a result of the remarkable physical
properties of water. Water absorbs heat better than the land because
the surface water can mix locally by convection. It also has a
remarkable storage capacity packing away large quantities of heat
with only slight increase in temperature. Once absorbed, this heat
is not lost; the water radiates it slowly out to the atmosphere. One
has only to consider the typically cool summers and mild winters of
coastal regions to appreciate the moderating inuence these
properties of water can have on the climate.
The equable climate of Western Europe owes much to the
inuence of the Atlantic and that well—known ocean current the
Gulf Stream. The Gulf Stream starts in the Straits of Florida,
between Florida and Cuba, and meanders north off the North
American coast until it reaches Newfoundland, where it veers off
towards Europe. On its trans—Atlantic journey the current splits,
sending a streak of warm water north past Scandinavia, and other
branches south past the Iberian Peninsula and Africa. Eventually
currents which head south ‘complete the circuit’ of the North
Atlantic gyre by reuniting with the Stream near the Bahamas.
Within this circle lies the Sargasso Sea, an expanse of warm still
water. The rapidly moving Gulf Stream forms a boundary which
The Last Resource
oxygen content; but plotting their ow still presents some formidable
problems.
The movement of water polewards from the equatorial regions is
not a simple convection system with warm water spreading north
and south from the equator, sinking at the poles and returning once
more to the equator as bottom water. Nevertheless the Sun’s heat
still plays a prominent part in ocean circulation. Cold currents, such
as the Peru, Benguela and West Australian Currents in the south
and the Oya Shio, Labrador and East Greenland Currents in the
north, move towards the equator to join in the gyres of water warmed
by the greater solar heating in the tropics. At the same time warm
currents, such as the Gulf Stream and the Kuro Shio in the north
and the Agulhas, Brazil and East Australian Currents in the south,
move towards the poles. In this way heat received from the Sun as
well as that permeating through the ocean oor from inside the
Earth is distributed over the planet.
If the Earth lived up to its name and had considerably more land
than oceans, it would be an unbearable place with temperatures
soaring during the day and dropping rapidly at night. The oceans
can act as a global thermostat as a result of the remarkable physical
properties of water. Water absorbs heat better than the land because
the surface water can mix locally by convection. It also has a
remarkable storage capacity packing away large quantities of heat
with only slight increase in temperature. Once absorbed, this heat
is not lost; the water radiates it slowly out to the atmosphere. One
has only to consider the typically cool summers and mild winters of
coastal regions to appreciate the moderating inuence these
properties of water can have on the climate.
The equable climate of Western Europe owes much to the
inuence of the Atlantic and that well—known ocean current the
Gulf Stream. The Gulf Stream starts in the Straits of Florida,
between Florida and Cuba, and meanders north off the North
American coast until it reaches Newfoundland, where it veers off
towards Europe. On its trans—Atlantic journey the current splits,
sending a streak of warm water north past Scandinavia, and other
branches south past the Iberian Peninsula and Africa. Eventually
currents which head south ‘complete the circuit’ of the North
Atlantic gyre by reuniting with the Stream near the Bahamas.
Within this circle lies the Sargasso Sea, an expanse of warm still
water. The rapidly moving Gulf Stream forms a boundary which