New data suggest the North Pole got a little thicker in
the 90s
By BBC News Online's Jonathan Amos
If ever you needed convincing that climate
science was complex stuff, just look at the
Arctic. We are told the sea ice in the northern
polar region is disappearing fast: some
computer models even suggest there could be
completely open water there during the
summers at the end of this century.
If this really is the
case, the implications
could be immense - and
not just for the polar
bears which rely on the
ice to go hunting for
seals. The cryosphere
plays a crucial role it
helping to regulate the
climate on planet Earth.
Satellites show a 3% reduction per decade, but assessing thickness is more difficult
An ice-free Arctic would likely accelerate any
global warming process that was taking place.
But a new, and as yet unpublished, piece of
research is challenging the idea that a big melt
is underway. Dr Greg Holloway, of the Institute
of Ocean Sciences in Sidney, Canada, has got
tongues wagging with his suggestion that the
missing ice is still there, piled up in locations
where researchers have not been looking for it.
The evidence for major thinning is supported
by submarine data. Upward-looking sonar
readings, studied by both US and British
scientists, have produced broadly similar
results: about a 40% reduction in draught
between the 1960s and 1990s - by draught,
researchers mean the difference between the
surface of the ocean and the bottom of the
ice pack.
But the submarine data are not exactly
comprehensive: the cruises were not
continuous and the data sets only cover
certain areas in the Arctic. And this is partly
what got Dr Holloway into thinking the ice may
simply have been "mislaid".
Satellite methods
He wondered if multi-decadal wind patterns
known to operate in the Arctic could have
shifted the ice into areas not surveyed by the
submarines, giving the illusion that the ice was
losing volume over a period of time. And when
he matched the timing of the submarine visits
with what he knew about wind cycles, his
suspicions were confirmed.
"It's a circumstance
where the ice tends to
leave the central Arctic
and then mostly pile up
against the Canadian
side, before moving
back into the central
Arctic again," he told
BBC News Online.
"Because of territorial
waters and where US
submarines weren't
allowed to go in the
1990s - the submarines
couldn't enter Canadian
waters and that's
where the ice was."
Polar bears use the ice to hunt for seals
Dr Holloway believes the fact that the British
research tallied with the American studies was
purely coincidental - a "fluke".
"Trying to get a picture of the volume of Arctic
ice is pretty sketchy," he said. "It's a question
of what other information we can bring to bear
so that we get a fuller picture. The great hope
for the future is that satellite methods may be
able to observe the thickness of the ice as
well as the extent."
But Dr Peter Wadhams, of the Scott Polar
Research Institute in Cambridge, UK, and one
of the world's leading experts on Arctic ice, is
not yet prepared to accept the Canadian's
analysis.
Stability returns
"It needs testing obviously, but I think on the
whole the evidence is against it," he told BBC
News Online. "There are some submarine data
sets from these regions that are not yet
published and they show no thickening, and
data from radar altimetry suggest thinning over
the entire Arctic, not just over the regions
where the submarine data exists."
Dr Wadhams said he
also thought some of
the theoretical basis
underpinning Holloway's
ideas was not
supported by what
science had learnt
about ice dynamics.
"Modellers suspect it is
not as simple as Dr
Holloway suggests -
the ice will not simply
pile up in some other
place. There will be a change in the
distribution of ice thickness around the Arctic
but it won't involve any massive build-ups to
compensate for overall thinning."
If the submarines have got it right then at
least some stability appears to have returned
to the Arctic. The latest and most
comprehensive analysis yet of the sonar data
collected in the 1990s shows little if any
thinning - at least towards the end of that
decade. Indeed, at the North Pole, there are
indications in the data that the ice even got a
little thicker.
For Dr Holloway, there is a recognition that he
needs to put his research through peer review
and get it published. "There are certainly
regional changes taking place," he said. "And if
you take the western Hudson Bay, it may well
be that the Polar bears are being stressed
there because of declining ice coverage. But I
believe we have been a little bit overly
stampeded into the idea that there is a terribly
alarming melting taking place."
-- Anonymous, May 03, 2001