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Tsunami Debris and North America: Is the Tail Wagging the Dog?


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Recent weeks have seen a spate of news articles (three examples here, here, and here) claiming that wreckage from the March 2011 Japanese tsunami has started arriving on the west coast of North America.

Is that likely?

First, a little perspective on just how big the Pacific Ocean is. About 70% of Earth is ocean. The Pacific makes up nearly half of that 70%. It is 64.1 million square miles in area. (The contiguous 48 U.S. states cover 3.2 million square miles.)

Land? Continents? What?

The Pacific is vast, and distances in the Pacific are vast. Japan lies 4,500-plus miles from North America. Nearly twice the distance from Washington, DC to San Francisco.

Reports of tsunami wash-ins mounted following a December talk by oceanographer Dr. Curtis Ebbesmeyer in Port Angeles, Washington. Let’s conservatively assume January 1 for an arrival date along the Washington state/British Columbia coast. That’s 296 days after the tsunami. The shortest line from Japan would push flotsam directly into the westward-flowing Alaskan Coastal Current. Instead, to reach Washington state, it would have to track further south, on a route not an inch less than 4,900 miles. A sustained average travel speed of 16.7 miles per day.

So, again, is that likely?

Look at what we know. The North Pacific Current runs generally west-to-east. But it is slow, wide, and inconsistent. In fact, in many spheres it’s simply known as the North Pacific Drift. Estimates of its average speed vary widely. The U.S. Navy reports a range of 2.5-8 miles per day (see p. 5); others say 3-4 miles per day. (This wonderful tracker using NOAA satellite data will help you visualize the exact speed and direction of Pacific surface currents for the entire year.)

Objects floating in this water follow a contorted path. Here’s a buoy track from the western North Pacific.

North Pacific buoy drift 1998

Here are many buoys tracked by satellite across the eastern North Pacific.

North Pacific buoy tracks 1976

Straight shot? Hardly. So add some more to that 4,900 miles. Now you’re asking drifting objects to travel over 20 miles a day. Not just one day — every single day.

For wash-in reports to be credible, one must make the leap from “much less than 8” to “over 20” miles a day. How? Insert the mystery variable: windage. A nice term for the effect that wind has on a floating object. Clearly a sailboat catching the wind moves faster than ocean currents alone would take it. Likewise, something riding high in the ocean, like a buoy, will probably get an assist from prevailing winds.

But there’s a lot of uncertainty in how much to factor windage into an equation. Especially the North Pacific westerlies, which are inconsistent and spotty through much of the summer — the time when they were supposedly pushing these buoys at 3-5 times the speed of the currents. (NOAA also shows a negative Arctic Oscillation for summer 2011, which tends to suppress the westerlies.)

In late September, a Russian research vessel found other bouyant, high-floating objects identifiably from the tsunami still thousands of miles from North America. They hadn’t even reached Midway Atoll yet. The best science suggests that these buoyant objects are still well over a year away from the West Coast.

So what gives?

Dr. Ebbesmeyer is convinced that the buoys found in Washington and British Columbia are from the tsunami. That, riding high, they found the shortcut that eluded most of their compatriots. However, his own article says that beachcombers have been finding identical buoys for years, and that the video of his December talk “went viral” on YouTube. It’s possible that more locals have simply started noticing them after hearing rumblings of incoming “tsunami debris.”

Which comes to the heart of the matter. We know three things for sure. First, tsunami material will wash up in North America. That’s the physical reality of how the oceans & winds work. Second, while not statistically impossible for Pacific debris to travel 5,000 miles in nine months, it would be very atypical. Third, and most important, thanks to a global culture of plastic, artifacts from Japan and elsewhere around the Pacific wash up in North America all the time. And vice-versa. See, for example, Kamilo Beach in Hawaii — the poster child of a plastic world.

Kamilo Beach

Finding Japanese buoys means that Japanese buoys were lost some time in the past. Anything beyond that is speculation. The Japanese fishing industry is enormous, in one year catching 6.626 million tons! They lose buoys. And a plastic buoy can survive intact in the ocean for decades.

The human tragedy of the March 2011 Japanese tsunami wrenches the heart. The possibility of finding physical remnants of that catastrophe — of piecing lives and stories back together — is compelling. But it can also be seductive, causing leaps of logic that end up telling the wrong tale. Which does nobody any good.

So to beachcombers, scientists, and journalists, please keep in mind what we don’t know. Resist the tail wagging the dog.

Images: Planet Ocean, from Google Earth, North Pacific buoy drift 1998 from http://swfsc.noaa.gov/publications/TM/SWFSC/NOAA-TM-NMFS-SWFSC-154_P267.PDF; North Pacific buoy tracks 1976, from http://muenchow.cms.udel.edu/classes/MAST602/Eastern_North_Pacific.pdf; “Kamilo Beach”, from Algalita.org at Wikimedia Commons.

Harold Johnson About the Author: Harold Johnson lives in Saco, Maine with his wife and young daughter. A freelance copyeditor and writer by trade, he spends his free time studying archaeology, earth sciences, and the ways the natural and manmade world have mingled across millennia. Since May 2010, he has written on marine debris and plastic pollution as The Flotsam Diaries. Follow on Twitter @FlotsamDiaries.

The views expressed are those of the author and are not necessarily those of Scientific American.






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  1. 1. SacoHarry 11:52 am 02/2/2012

    Please note. As of this morning, the link to the Navy’s report on current speed is broken. It can be found here: http://www.nmfs.noaa.gov/pr/pdfs/permits/goa_deis.pdf, Section 3.3, p. 5

    Link to this

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