Science topics
Ocean currents - George Cresswell.
The Scientist
I am an oceanographer interested in the ocean currents and water
properties in the oceans around Australia. The thrust of my work
is to make a contribution to the understanding of the ocean currents
around Australia, in SE Asia, PNG, New Caledonia and Cuba. I go
to sea, work with satellites and CTDs (a device that measures temperature,
salinity and depth) in order to describe and differentiate different
water masses and their movements.
George's collaboration is with artist Jock
Young.
The Research
My work includes: Collecting and analysing data from research voyages
on a variety of vessels; analysing data collected by instruments
moored on the continental shelf and the deep ocean; interpreting
satellite images.
This research finds application in the projects that I conduct
for private industry and in the ocean current reports that I give
to competitors in the Sydney to Hobart yacht race -- and other races.
I have selected four sets of diagrams for this note. The first
is a panel of four items assembled for the Sydney
to Hobart yacht race in 2000:
- Item 1 gives details about satellite images.
- Item 2 is a movie of the sea surface temperature patterns that
were detected by satellite in the months leading up to the race.
- Item 3 is a satellite temperature image onto which I have superimposed
my estimates of the ocean currents.
- Item 4 gives the sea surface topography measured by a radar
altimeter on a satellite. The high regions are analagous to high
pressure regions in the atmosphere -- the fluid flows (water and
air respectively) around both are anticlockwise. Oceanographers
at CSIRO have made estimates of the currents using various formulae
and these appear as arrowheads.
The second is a map (1) showing the tracks of drifters with transmitters
and sea anchors (to lock them to the sea so that the wind won't
blow them around) as they are carried in loops around an anticlockwise
eddy ( a high -- see the paragraph above) that is itself being carried
along. The + signs show successive noon positions.
The third is a map (2) showing current vectors in an anticlockwise
eddy that we measured from our research vessel "Franklin".
The fourth is an image showing the colour of the sea off SE Australia
(image to come). This was formed from the measurements taken by
a satellite. The colours give an indication of the amount of chlorophyll
-- or algae, or phytoplankton -- in the surface waters. Waters that
are nutrient-rich and exposed to the sun then photosynthesise. The
currents drag out the patterns of chlorophyll so that the effect
is like throwing oil paint in your bath and then swirling it around.
The examples above are only a few of those that we use to understand
the ocean currents and water properties and the effects that these
have on algae -- the base of the foodchain -- in the waters around
Australia.
Additional information:
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