From the archive, originally posted by: [ spectre ]

http://environment.newscientist.com/article.ns?id=mg19426075.400&feedId=online-news_rss20
Global warming is speeding up ocean waves / 12 June 2007

Gigantic ocean waves, spanning hundreds of kilometres from crest to
crest, have been speeding up thanks to global warming, a new model
suggests.

Geophysicists predict that as the ocean surface warms, these so-called
planetary waves should speed up. To test this idea, John Fyfe and Oleg
Saenko at the University of Victoria in British Columbia, Canada,
modelled the changes to ocean wave patterns over the 20th and 21st
centuries.

“We were really surprised at how quickly the ocean responded to
temperature change,” Fyfe says. According to the model, global warming
has already increased the speed of the waves, but no one noticed
because satellites have not been monitoring their speeds for long
enough, he says. The model also shows that by the end of the 21st
century, the waves will be a further 20 to 40 per cent faster compared
with pre-industrial speeds (Geophysical Research Letters, vol 34, p
L10706).

“We knew we’d see an effect, but we didn’t think it would be
significant for at least another two centuries,” Fyfe says. The faster
planetary waves will have an effect on global weather, he adds.

From issue 2607 of New Scientist magazine, 12 June 2007, page 23

http://www.agu.org/pubs/crossref/2007/2007GL029859.shtml

Abstract
We have analyzed a suite of state-of-the-art climate model
simulations, and show that anthropogenic warming of the upper ocean
produces a detectable speed-up of low-latitude North Pacific oceanic
planetary waves by the end of the 20th century. The projected percent
increase in propagation speed for the end of the 21st century is about
35% (relative to pre-industrial) following one of the standard
emissions scenarios from the Intergovernmental Panel on Climate
Change. This remarkable simulated effect of oceanic warming on
planetary wave propagation speed portends important observed change in
interannual climate variability.

Human-induced speedup of oceanic planetary waves

Oceanic planetary waves are long-wavelength westward traveling waves
whose origins are linked to the shape and rotation of the Earth.
Critical to transmitting energy and nutrients throughout the ocean,
they can intensify western boundary currents such as the Gulf Stream
and the Kuroshio Current. Standard theory about these disturbances
predicts that propagation speed increases as density differences in
the ocean’s water column become more sharply delineated. Fyfe and
Saenko (2007) noted that human-induced ocean warming over the past 40
years, which has likely increased the density contrast between the
surface and deep ocean regions, could be inducing increases in oceanic
planetary wave speeds. Through analysis of climate models, the authors
found that human-induced ocean warming has likely already produced a
detectable speedup of low-latitude North Pacific oceanic planetary
waves. Further, by the end of the 21st century, oceanic planetary wave
propagation speed is likely to increase by 35% relative to
preindustrial times, provided that emissions scenarios from the
Intergovernmental Panel on Climate Change come to pass. The authors
expect that these wave speedups will have important effects on
interannual climate variability.

Published: 24 May 2007

CONTACT
Dr. Oleg Saenko
E-mail: Oleg [dot] Saenko [at] ec [dot] gc [dot] ca

Dr. John Fyfe
E-mail: John [dot] Fyfe [at] ec [dot] gc [dot] ca