Super Waves

Super Waves
I just finished reading a new book, The Wave; In Pursuit of the Rogues, Freaks, and Giants of the Ocean by Susan Casey and it inspired me to write this short blog on the subject. The most astonishing fact is that more than 200 supertankers, container ships, and bulk carriers over 350 feet in length have been lost at sea over the past 20 years due to severe weather and huge waves: more than one every two weeks on average. If this happened in the aviation industry it would be front-page news. However, most of these ships are owned by and manned by crews from third world countries and so their loss and the deaths of their crews (that run in the hundreds if not thousands) go unrecorded in the media.

Giant waves may be classified in basically five categories:

1. ‘Big Splashes’: the result of a landslide, volcanic eruption, or calving of a glacier.

2. ‘Tsunamis’: the result of an undersea earthquake.

3. ‘Storm Surges’: the result of a tropical storm or very powerful cyclone.

4. ‘Big Surf’: huge shoreline waves generated by large cyclonic storm systems.

5. ‘Rogue or Freak Waves’: mysterious storm-generated waves that tower two to four times higher than other waves in the vicinity. On very rare occasions the wave occurs without a storm present.

I list, albeit briefly, the most extreme cases of such in modern records.

BIG SPLASHES

The biggest splash of all (that scientists are aware of) was that in Lituya Bay, Alaska on July 9,1958. Lituya Bay is an arm of the much larger Glacier Bay in Southeastern Alaska and was carved by retreating glaciers from the Brady Icefield. A 7.3 earthquake caused a massive landslip on the south shore of the bay creating a gigantic wave some 1,740-feet high that swept across the opposite shoreline and Cenotaph Island. Two people camping and fishing in the bay died.



The photo shows an aerial view of a hillside that was inundated by a 1,700-foot wave during the ‘big splash’ following an earthquake-caused landslide in Lituya Bay, Alaska in July 1958. Photo from U.S. Coast and Geodetic Survey.




This map shows Lituya Bay and what the estimated run-up levels of the wave were during the event. Illustration from geology.com

TSUNAMIS

Earthquake-generated tsunamis are, like ‘Big Splashes’, of geologic- rather than meteorologic-origin. The Boxing Day earthquake off the coast of Sumatra (9.3 on the Richter scale) on December 26, 2004 generated what is likely the largest tsunami in modern history. An extensive section of shoreline south of Banda Aceh, on the northern tip of Sumatra was struck by a tsunami averaging 80 feet in height with a maximum height of 115 feet estimated to have come ashore between Labuhan and Leupung. The run-up was measured some 170 feet in the hills in this region. One city alone, Meulaboh, suffered the worst casualties of all: 40,000 of the 120,000 residents perished. However, tsunamis, like storm surges, are not so much waves as they are walls of water with no ‘back trough’ behind them.



A graphic illsutrating how an 80-foot wave compares to a 6-foot human.

STORM SURGES

I shall assume you all know what a storm surge is. What the greatest such in modern records might be is debatable. Without doubt the deadliest was that which conquered the Brahmaputra River Delta of Bangladesh on November 12-13, 1970. The surge was some 40 feet high and drowned 300,000-500,000 people. The Great Boha Cyclone remains the deadliest tropical storm in human history. As I mentioned above, storm surges like tsunamis, are walls of water not waves.



This map illustrates the storm surge that occurred during the great Boha Cyclone of November 12, 1970. The graph shows the depth of the storm surge on a scale up to 48 feet high.Graph from WMO ‘Climate into the 21st Century’ published by Cambridge University Press, 2003.

Even higher storm surges have been reported. The famous Bathurst Bay Cyclone of March 5, 1899 apparently crushed Australia’s Queensland State with a 42-foot storm surge according to survivors. This is the record highest storm surge we have corroborated by eyewitnesses.

BIG SURF

The largest surf in the world occurs along the northern and eastern shores of the Hawaiian Islands and select locations along the California and Baja of Mexico coast. The biggest waves occur when powerful winter storms in the Alaskan Aleutian Islands and Gulf of Alaska generate a sort of ripple effect that streams across the North Pacific and spawn the waves that occasionally crash ashore in the above referenced regions. Of course, the biggest waves don’t actually come ashore but are confined to the reefs and shoals some miles from the actual coastline. Big-wave surfers (well documented by a breathless Ms. Casey) ride 70 and 80-foot monsters and wait for the day that a 100-footer will test their skills. According to Casey’s book the site that has the best potential to produce 100-foot plus big surf is the Cortez Bank, a submerged chain of mountains about 115 miles west of Point Loma, San Diego County, California.



Laird Hamilton, probably the greatest big-wave surfer in the world, at work on what looks like a 70-footer. Still from his movie Laird.

ROGUE OR FREAK WAVES

On February 8, 2000, the British research ship Discovery accurately measured a gigantic 98-foot high wave while on a scientific expedition 155 miles west of the coast of Scotland. The wind had been blowing at 50mph or greater for over 12 continuous hours in the vicinity of the observed wave. This is the highest ‘officially’ measured wave at sea. The U.S.S. Ramapo recorded a 112-foot wave near the Philippines during a typhoon in February 1933 and the report seems legitimate. It has become apparent that such monsters are not as rare as previously thought. Many large vessels have simply vanished after encountering what one presumes were rogue or freak waves. Cruse ships face a serious threat as well: in February 1995 the Queen Elizabeth 2 encountered a rogue wave of some 100 feet (estimated) in The North Atlantic that almost foundered the iconic vessel.

In fact, so many large ships have been lost that it begs the question why nobody seems to care aside from Lloyd’s of London, the premier marine insurance agency.



The supertanker ‘World Glory’ split in half and sank after a 70-foot rogue wave crushed her off the coast of South Africa in 1968. Photo courtesy of South African Sailing Directions.

REFERENCES:

The Power of the Sea; Tsunamis, Storm Surges, Rogue Waves, and Our Quest to Predict Disasters by Bruce Parker, Palgrave Macmillan, 2010.

The Wave: In Pursuit of the Rogues, Freaks, and Giants of the Ocean by Susan Casey, Random House, 2010. NOTE: This book largely deals with ‘Big Surf’ and the surfing community that seeks out the biggest of the big waves. It does, however, have several good chapters on other super-wave events.

THANKS: To Jerry Alexander for bringing this interesting subject to my attention!