Feature: Ocean-Observing Satellites Help Break Current Records

Feature

February 18, 2008

Ocean-Observing Satellites Help Break Current Records

Two different teams of ocean adventurers set records this winter crossing the Tasman
Sea. One was the first expedition to kayak from Australia to New Zealand; the other was
the first Australians to row across the Tasman Sea. Both took advantage of something
that sailors have been relying on since the launch of Topex/Poseidon in 1992–maps of
ocean currents made possible by ocean altimetry.

The teams consulted with David Griffin, a research scientist with Australia's
Commonwealth Scientific and Industrial Research Organisation. Griffin creates maps of
the local waters using sea surface height measurements from the Jason-1, Envisat and
Geosat satellites to calculate the location, speed and direction of currents. These maps,
which also include sea surface temperature, are available online at

http://www.cmar.csiro.au/remotesensing/oceancurrents/ .

"The difficult thing about this region is the strong and variable currents," says Griffin,
who has worked with many different groups including fishermen, yachtsmen, police,
search and rescue personnel, and environmental protection agencies. Griffin is a principal
investigator on the Ocean Surface Topography Science Team, an international group of
researchers selected to work on the Jason mission. Topex/Poseidon and its successor
Jason-1 are joint missions of NASA and the French space agency, Centre National
d'Estudes Spatiales.

The rowers set off for Australia from New Zealand on Nov. 29, and Griffin received
hourly notices of their boat's position. "We had a script going that updated, every hour,
what their trajectory would be if they choose various headings to paddle on," says
Griffin. "Andrew Johnson, the expedition's navigator, had studied the maps on our Web
site during preparation for the voyage, so he had a pretty good idea of the array of
obstacles and opportunities the ever-changing eddy field of the East Australian Current
was likely to present."

"We were certainly lucky with the currents," says Johnson, "but being aware of them was
half the battle. At least then you could minimize the negative impact and maximize the
positive."

After 32 days at sea, the four Australian rowers successfully completed the 2,200-
kilometer (1,400-mile) journey on Dec. 30, 2007. The first rowing crossing, done by a
single New Zealander in 1970, took 67 days.

The kayakers began their voyage across the "ditch," slang for the Tasman Sea, on Nov.
13, 2007. "They made their tactical decisions by using Google Earth to overlay their
waypoints on a map of sea surface temperature imagery and altimetric currents that we
provide on our web site," says Griffin. They had hoped to make it to New Zealand by
Christmas. Instead, they arrived on Jan. 13 after 62 days at sea. "We were biting our
fingernails," says Griffin.
The launch of the Ocean Surface Topography Mission on the Jason-2 satellite this
summer will help ensure that critical ocean altimetry measurements continue into the next
decade.

More information on the "Base 3 Rowing Challenge" is available at

http://www.basefx.com.au/expedition/?cat=3

and on the "Crossing the Ditch" kayak
expedition at

http://www.crossingtheditch.com.au/ .

-end-

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