Research Re-discovery of the Obvious

July 20, 2017

I get things in my RSS feeds. Most of the time interesting. Sometimes it’s “What the XXX?”.

Ocean Science Journal just published a peer-reviewed items “The “shallow-waterness” of the wave climate in European coastal regions” (Christensen, K. H., Carrasco, A., Bidlot, J.-R., and Breivik, Ø.: The “shallow-waterness” of the wave climate in European coastal regions, Ocean Sci., 13, 589-597, https://doi.org/10.5194/os-13-589-2017, 2017).

The Abstract (emphasis added by me):

In contrast to deep water waves, shallow water waves are influenced by bottom topography, which has consequences for the propagation of wave energy as well as for the energy and momentum exchange between the waves and the mean flow. The ERA-Interim reanalysis is used to assess the fraction of wave energy associated with shallow water waves in coastal regions in Europe. We show maps of the distribution of this fraction as well as time series statistics from eight selected stations. There is a strong seasonal dependence and high values are typically associated with winter storms, indicating that shallow water wave effects can occasionally be important even in the deeper parts of the shelf seas otherwise dominated by deep water waves.

Where to start?

  • The distinction between “deep” and “shallow” water waves is artificial. Water follows the laws of nature regardless of water depth. Mankind has invented mathematical equations of motions for waves. The depth of the water and the wave height (profile) are part of of those equations. For “deep” water the affect of water depth on the computed equations of motion is minor and can be disregarded. That is a fortuitous because the equations are so much harder (impossible?) to solve mathematically if the water depth is not ignored.
  • The use of the word “consequences” seems to be inflammatory. Certainly suggests “dangerous” to the un-informed. What are the consequences other than for the work to solve the difficult equations of motions?
  • Of course there are “seasonal dependance”! In some seasons the wind blows and make big waves. Sometimes the waves are small even in shallow water and thus can be assumed to be “deep water” waves. And if the wave heights are big enough so that the water depth effects are not minor, then by definition they become “shallow-water” waves! Of course. Where is the news in this?
  • These things seem to “important” only to those who are looking to use the easy wave equations to assume “deep” water when in fact the water is “shallow”.

I can’t figure out from the abstract why I should bother reading the paper. My bad.

I spent a couple of years in grad school and early career in the 1970’s trying to simulate shallow water waves and their affect on wave power machines, moored ships, etc.

I really wonder who funded this study and why