Restless Energy
153
the parent current. The Gulf Stream which comes into contact with
the ‘ice currents’ meanders as it progresses across the Atlantic, and
from time to time loops become so exaggerated that they break
away completely. Patches of cold water trapped in a detached eddy
can last as long as six weeks, slowly drifting south. Every spring,
therefore, the Ice Patrol has to study anew the detail of currents in
the vicinity of Newfoundland, particularly over the shallow ocean
area which shermen know as the Grand Banks.
The area covered by the International Ice Patrol is small compared
with the total world ocean, and yet even in this restricted area one
sees
just how variable apparently distinct phenomena such as
currents can be. Plots of their paths on ocean maps generally record
the average direction of a ow which may uctuate appreciably from
day to day. This variation over quite short spams of time is shown
particularly clearly in records of deep—ocean currents. Deep—water
movements can be tracked in some detail by the use of underwater
oats, sometimes called ‘pingers’, devised by Dr John Swallow of
the British National Institute of Oceanography. The Swallow float
can be made to stay at any specied depth, and, as it moves with the
current, brief blips of sound emitted from it allow a surface vessel
to plot its position—continuously, if necessary. Different ows in
terms of both speed and direction have been detected with this
technique at the same station within a period of days. Similarly,
experiments with anchored instruments indicate that records
taken over periods as long as a week can still be at variance
with the ‘average conditions’ subsequently found to exist at their
location.
'
Does this variability of the ocean environment place it beyond any
kind of forecasting? Fortunately the answer must be a qualied ‘no’.
Although the inner world of the ocean uctuates far more than had
been imagined in the past,
face it presents to the atmosphere is
far more predictable if still bairely better understood. As far as the
weather is concerned, the oceans have some advantages over the
land. For a start, they are atter. Secondly, the heat capacity of
the water means that the temperature is the same over large areas and,
even when it changes, it does so slowly. Such features are highly
desirable from the weather forecaster’s point of view; an embryo
storm born at sea grows to maturity in a fairly predictable way,
which in turn makes related forecasts of conditions such as the state
of the sea much more accurate.
153
the parent current. The Gulf Stream which comes into contact with
the ‘ice currents’ meanders as it progresses across the Atlantic, and
from time to time loops become so exaggerated that they break
away completely. Patches of cold water trapped in a detached eddy
can last as long as six weeks, slowly drifting south. Every spring,
therefore, the Ice Patrol has to study anew the detail of currents in
the vicinity of Newfoundland, particularly over the shallow ocean
area which shermen know as the Grand Banks.
The area covered by the International Ice Patrol is small compared
with the total world ocean, and yet even in this restricted area one
sees
just how variable apparently distinct phenomena such as
currents can be. Plots of their paths on ocean maps generally record
the average direction of a ow which may uctuate appreciably from
day to day. This variation over quite short spams of time is shown
particularly clearly in records of deep—ocean currents. Deep—water
movements can be tracked in some detail by the use of underwater
oats, sometimes called ‘pingers’, devised by Dr John Swallow of
the British National Institute of Oceanography. The Swallow float
can be made to stay at any specied depth, and, as it moves with the
current, brief blips of sound emitted from it allow a surface vessel
to plot its position—continuously, if necessary. Different ows in
terms of both speed and direction have been detected with this
technique at the same station within a period of days. Similarly,
experiments with anchored instruments indicate that records
taken over periods as long as a week can still be at variance
with the ‘average conditions’ subsequently found to exist at their
location.
'
Does this variability of the ocean environment place it beyond any
kind of forecasting? Fortunately the answer must be a qualied ‘no’.
Although the inner world of the ocean uctuates far more than had
been imagined in the past,
face it presents to the atmosphere is
far more predictable if still bairely better understood. As far as the
weather is concerned, the oceans have some advantages over the
land. For a start, they are atter. Secondly, the heat capacity of
the water means that the temperature is the same over large areas and,
even when it changes, it does so slowly. Such features are highly
desirable from the weather forecaster’s point of view; an embryo
storm born at sea grows to maturity in a fairly predictable way,
which in turn makes related forecasts of conditions such as the state
of the sea much more accurate.