New buoys measure Australia's wildest seas
Tue 24 Sep 2019.
The BoM recently replaced two of its ocean wave-monitoring buoys in the Southern Ocean. The buoys, which are exposed to the full force of the Roaring Forties, lie 10km W of Cape Sorell on Tasmania's West Coast and 7km W of Cape du Couedic at the SW tip of Kangaroo Island, SA.
The new Triaxis wave buoys have the ability to record wave direction as well as height and other parameters, and you can see them in green on the links above. The long-standing Cape Sorell buoy replaces one installed by the Bureau in January 1998 which in turn followed wave-monitoring on Tasmania's West Coast by the CSIRO. It's thought the highest wave recorded by the BoM's earlier Cape Sorell buoy was 18.4m on 16 September 2010 which was reported in The Age‡, complete with a tram for comparison. A reported 19.5m wave in 2006 has been dismissed as an error. The higher 19.83m wave recorded on 29 July 1985 was measured by the CSIRO buoy.
The two buoys are in a select company of Southern Hemisphere wave-measuring buoys monitoring Southern Ocean wave physics in the world's stormiest and least studied waters. The highest wave measured in the Southern Ocean was 22.03m south of TAS in 2012 until that record was broken by a Triaxis buoy moored off Campbell Island by New Zealand's MetOcean in 2018. Only 4 months after deployment, it measured a massive 23.8m wave on 8 May 2018. For comparison, here is the 24.38m monster off Nazaré, Portugal, that put Brazil's Rodrigo Koxa into the record books for the highest officially-measured wave ever surfed. It's important to note, though, that open ocean waves can't be compared with waves breaking on a shore. As a wave approaches a shoreline, it moves into shallower and shallower water, and the energy that's been propelling the wave forward has nowhere to go but up and the wave grows taller as a result.
For some interesting comparisons with Northern Hemisphere waves in the Atlantic Ocean, you may find this 2017 AWN Blog an interesting read. The highest scientifically recorded North Atlantic wave has been 29.1m from trough to crest. it also discusses the fascinating rogue waves, where sequences of waves align to produce one or more waves that can be twice or more the height of their neighbours. The highest measured one was the famous Draupner wave which was measured at 25.9m as it swept under Draupner E oil platform in the North Sea. All these are pussies, though, compared to the rockfall-generated tsunami that tore down Lituya Bay, Alaska, following an earthquake late in the evening of 9 July 1958. The wave this created sloshed up the steep sides of the bay removing all trees and vegetation to heights of up to 524m above sea level. The event is covered in detail, complete with an eyewitness account, in this Wikipedia article.
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