Monday, August 15, 2011

Pacific may hold key to Atlantic Hurricanes

A deep dive into current cyclone activity.
Ryan Maue, mentioned in this story, is one hurricane geek to keep an eye on. He's currently hanging his hat at Naval Research Laboratory Monterey.
From the Sarasota Herald-Tribune:
Hurricane Bill spins in the Atlantic Ocean in 2009. In 2010, global hurricane activity hit a record low. 
But the Atlantic saw its third-busiest hurricane season on record, underscoring a trend that has emerged 
since the mid-1990s.

If the world seems dizzy with nonstop hurricanes, look beyond the Atlantic Ocean. It turns out that ocean is getting more than its fair share of strong, long-lived storms lately.
The reasons may lie in the Pacific.

Last year, global hurricane activity hit a record low. But the Atlantic saw its third-busiest hurricane season on record, underscoring a trend that has emerged since the mid-1990s.

Only 69 tropical storms formed worldwide in 2010, compared with the typical 80 to 90. Historically, Atlantic storms account for about 9 percent of the world's activity — measured by their number, as well as their strength and duration — but that has doubled more recently. Last year, the Atlantic's contribution was a remarkable 30 percent.

None of the Atlantic storms last year hit the U.S., but they did strike Newfoundland, Mexico and several Caribbean nations.

Whether the Atlantic will continue to make up for a drop in hurricane activity throughout the rest of world is unclear, but the implications are important for Central and North America, where people may have to contend with more storms.

Scientist Ryan Maue documented the shift in a study published last month in the journal Geophysical Research Letters, and explained the weather trends responsible. He stopped short of linking the change to global warming because the 40-year data set is too short and the effect of a warmer planet on hurricanes is indiscernible now, compared to other influences.

"In order to determine what's going on globally in terms of tropical cyclones, you have to look in the Pacific," Maue said.

He said the Pacific is such a large ocean basin that its influence on global weather is almost as important as the Earth's orbit, which is responsible for seasons.
"The trick is that it's been changing quite a bit recently," he said.
The research raises questions about whether the Atlantic activity may be compensating for changes in the Pacific, reflecting the role that tropical storms and hurricane play climate-wise.
Hurricanes can cause terrible destruction when they hit land. But, Maue said, they are vitally important for balancing heat energy in the oceans.
Pacific in flux
Whether the Atlantic is responding to a global need to balance hurricane activity, the warmth of its own tropical seas or a combination is uncertain.
Some scientists draw the biggest link between an increase in Atlantic hurricanes and warm Atlantic temperatures since 1995.

Most also agree that the Pacific plays a big role; how much is the question.
El Niño and La Niña, the names given to the respective warming and cooling trends of the equatorial Pacific, are blamed for just about everything weather-related, including slow and busy hurricane seasons in the Atlantic.

The explanation may seem overly simplistic, but the Pacific's power to influence weather is enormous, Maue contends. And it extends beyond El Niño and La Niña to the northern Pacific as well.

Scientists theorize that the Pacific and the Atlantic both go through cool and warm phases that last decades. The Atlantic is in a warm phase and the Pacific may be moving toward a cool phase.

The Pacific shift is unusual though, compared to recent decades. El Niño and La Niña are changing more frequently, with an uptick in La Niñas....MORE