Waves getting taller, stronger

It's one of the most treacherous stretches of water in the world, where 1 million cubic feet of water a second collide with 20- or 30-foot ocean swells over a four-mile stretch of shifting sand.

A small band of pilots brave often-treacherous conditions to guide ships across the Columbia River Bar.

The pilots who work the “Graveyard of the Pacific” have a deep respect for the relentless forces they face daily as they ride out to tankers, bulk carriers, car carriers, and cargo and passenger ships standing offshore. They commute in 72-foot self-righting boats that can roll over 360 degrees as winter gales and sometimes hurricane-force storms blast out of the North Pacific.

The pilots also confirm what marine scientists have just started discussing – ocean waves are becoming bigger and more powerful, and climate change could be the cause.

“We’ve been talking about it for a couple of years now,” said Capt. Dan Jordan, who served in the merchant marine for 30 years before becoming a Columbia River Bar pilot. “Mother Nature has an easy way of telling us who is in charge.”

Using buoy data and models based on wind patterns, scientists say the waves off the coast of the Pacific Northwest and along the Atlantic seaboard from West Palm Beach, Fla., to Cape Hatteras, N.C., are steadily increasing in size.

And, at least in the Northwest, the larger waves are considered more of a threat to coastal communities and beaches than is the rise in sea level accompanying global warming.

Similar increases in wave height have been noticed in the North Atlantic off England.

Unclear is whether the number and height of rogue waves beyond the continental shelf have increased.

The existence of such freak waves, which can reach 100 feet or more in height and can swamp a large ship in seconds, wasn’t proved until 2004, when European satellites equipped with radar detected 10 of them during a threeweek period.

“Obviously, this is an issue we are interested in,” said Trevor Maynard of Lloyd’s of London’s emerging risk team, which tracks global climate change developments. “We are seeing climate change fingerprints on a lot of events.”

BIGGER EVERY YEAR

Since the mid-1970s, buoy data show that the average height of the biggest waves off the Northwest coast has increased about 4 inches a year, or about 10 feet total, according to Peter Ruggiero, an assistant professor of geosciences at Oregon State University and the lead author of a study published recently in the journal Coastal Engineering.

Ruggiero and his colleagues also estimated the height of a “100-year” wave – the largest waves expected to come along every century. The estimate has increased 40 percent since the 1970s, from 33 feet to 46 feet. Some calculations estimate that a 100-year wave might be 55 feet high, taller than a fivestory building.

“We are assuming the trends will increase in the future,” Ruggiero said.

But the future already may be here.

Jordan, the Columbia River pilot, said a 44-foot wave was recorded off the river in October. In a major spring storm in 2007, a 54-foot wave was recorded.

“After that, the buoy quit recording,” Jordan said.

On the East Coast, a yetto-be-published study has also found that average wave heights have been increasing by a couple of centimeters or so a year.

“The averages aren’t very exciting,” said Peter Adams, an assistant professor in the University of Florida’s Department of Geological Sciences who used wind data from the past 20 to 30 years to develop a wave-height model. “Given that there are 3 million waves a year, one wave every 10 seconds, it’s not so alarming.”

Adams said that what he finds startling is that the height of the biggest waves has increased nearly one foot in 10 years.

“In a lifetime, that can be profound,” he said.

OCEAN MYSTERIES

A scientific debate is raging over what’s causing the increase in wave size. Possible causes include changing storm tracks, higher winds and more intense winter storms, all signs of global climate change.

“While these increases are most likely due to Earth’s changing climate, uncertainty exists as to whether they are the product of humaninduced greenhouse warming or represent variations related to natural multidecadal climate cycles,” Ruggiero’s study found.

Among the weather phenomenon that could be affecting wave heights in the Pacific, Ruggiero said, are El Niño – warmer surface temperatures in the tropical eastern Pacific — and the Pacific Decadal Oscillation – 20- to 30-year patterns of warmer or cooler surface temperatures in the Pacific.

“There is a lot of speculation, a lot of reading of tea leaves,” he said.

Others are skeptical about any link to climate change.

Richard Seymour, head of the Ocean Engineering Research Group at the Scripps Institution of Oceanography in California, said any connection between increased wave height and climate change was tenuous. In fact, Seymour said, there wasn’t enough data on wave heights to provide the “statistical reliability” to predict any trends.

Seymour and others said too little is known about the oceans. “It always struck me as odd we know more about the surface of Mars than the floor of the Pacific Ocean,” he said.

ERODING COASTLINE

Coastal planners in the Northwest are well aware of the problems posed by increasing wave heights. George Kaminsky, a coastal engineer with the Washington state Department of Ecology, said the main concern is erosion, adding that last winter there was phenomenal erosion on the southern end of the state’s Long Beach Peninsula.

“That data is convincing,” Kaminsky said. “It is a concern for us in Washington state. Sea level rise gets a lot of attention, but if the waves get higher, that could be more of a problem.”

Along the Columbia River, said Jordan, the river bar pilot, the Peacock Spit on the north end of the Columbia’s mouth and Clatsop Spit to the south are eroding, and some of the jetties have been damaged by the higher waves and more intense storms.

When conditions get too rough, the Coast Guard closes the bar. The bar was closed for several days last month, and Jordan said that typically the bar is closed four or five times each winter.

Not only are the waves getting bigger, Jordan said, but they’re getting more powerful, driven by increasingly intense storm systems.

In all his years at sea, Jordan said, the biggest wave he’s seen was about 60 feet high. When the big swells collide with the water flowing out of the Columbia, Jordan said, it can get ugly really quickly on the bar.

“These aren’t beautiful waves,” he said. “It’s nothing you would want to surf.”

This story was originally published November 26, 2010 at 5:45 AM with the headline "Waves getting taller, stronger."