14 December 2009

Storm Frequency in Japan Tied to El Nino

Posted by Michael McFadden

A new study suggests that Japan has been pounded by unusually strong typhoons at very regular periods over 6000 years. If climate change brings an increase in El Nino-like years, as some predict, Japan may be able to expect more stormy years.

Jon Woodruff of the University of Massachusetts, Amherst, and a team of scientists took 6-meter-deep cores from two lakes in Japan, going back about 6000 years. These lakes are close to the sea but separated by a thin strip of land.  Every few hundred years or so, the tranquil, seasonal sediment lines of the lake were obliterated by ocean material – marine species and coarse sand – which had crossed the land barrier and washed into the lakes during strong typhoon strikes.

By comparing this sediment record with others, they found that these typhoon strikes coincided with increased El Nino-like conditions elsewhere in the world. In addition, the periods of increased storms were separated by hundreds of years of calm, showing that there is a longer cycle of El Nino variation, operating on hundreds and maybe even 1000 years.

“The geologic record really gives us a powerful tool to get data for how hurricanes behave on multi-decadal and longer time spans,” said Woodruff.  “There is uncertainty about how tropical cyclones will behave in the future because the written record of hurricanes is so short.”

The El Nino southern oscillation, which occurs about every 3-5 years, brings warm water from the West Pacific to the East Pacific, causing dramatic weather changes to Pacific coastlines. Because of the shift, storms form farther out in ocean and have more time to build up strength and curve to hit Japan instead of China. During those times, there is typically less hurricane activity in West North Atlantic.

Some scientists suggest that climate change may mean more El Nino like conditions in the future.  This study provides one more piece to the puzzle to show what we can expect if that’s true.

“It’s preliminary work but it’s exciting because tropical cyclone activity is behaving in response to El Nino southern oscillation the way we would expect it to behave, but at very long time scales,” said Woodruff.

–Gwyneth Dickey, UC Santa Cruz Science Communication Graduate Student