This is what #ocean #swells look like over time. In this graphic the horizontal axes are time and the vertical axes are wave period. The colours represent the amount of energy in a particular wave period. The top panel is from an #aquadopp wave gauge located outside the barrier reef in 12 m of water and the lower panel is another instrument located inside the reef in 2.5 m of water. Each vertical black line denotes a separate swell hitting the west coast of #Mauritius We can see that over the time period of 1 month, 7 separate swell pulses were recorded. These swells were generated by storms in the southern #IndianOcean. As waves travel in deep water, longer period waves travel faster, that is why each swell event is clearly demarcated by a sudden increase in energy in longer wave periods. Storms generate waves over a wide range of wave periods, so as the shorter period waves arrive later, we see the amount of energy in those shorter periods increase as the energy in the longer periods dies out. The separation of waves in to different periods travelling at different speeds is known as #dispersion. The effect of the barrier reef is also evident in the overall reduced energy at the inshore wave gauge. Despite the waves breaking on the outer reef and knocking out most of the wave energy, we still see the tell-tale dispersive signature of a swell with the long periods hitting first, followed by the arrival of shorter period #waves. Cool, no? #eCoast @ecoast_nz
