Thursday, August 10, 2017

Making Waves

Light, the solar workhorse, transmits energy from the sun that makes things happen on earth. Light makes waves, a result of wind passing over water surfaces. The wind is solar powered.

Breaking swells, Halibut Point
As long as the sun shines and the earth turns there will be wind, globally speaking, because air temperatures vary from day to night and our atmosphere warms/cools at different latitudes, elevations and planetary surfaces. These variations lead to imbalances in atmospheric pressure. The air moves responsively to equalize the pressure, creating wind. The friction of air movement over water, whether puddles or oceans, causes ripples that can be amplified into waves.
Great Black-backed Gull and Great Cormorant
Water responds to the energy imparted to it. It becomes a fluid energy vehicle, an energy transportation system. Wind waves are a prominent part of that system. When the waves encounter land their energy transforms the water dramatically into surf.
Herring Gull
The sudden reconfiguration of waves into surf creates challenges, opportunities, and entertainment for coastal dwellers. The forces involved can be tremendous and relentless. Adaptive strategies are usually more effective than resistance.
Common Eiders feeding within the surf zone
The flow of air causes disturbances to the water surface that may initially appear random. Steady winds blowing over a long enough distance will merge the waves and cause crests to form into what is called a sea, aligned rhythmically in the direction of the wind. Stormy conditions can make the pattern locally chaotic.
The wind energy imparted to waves results in an orbital motion to a column of water. The height of the water column is equal to half the length of the wave, that is, half the distance between wave crests. The waves carry that energy toward the horizon but the water itself scarcely moves forward, revolving essentially in one place while the energy passes on, often very long distances.
Swells breaking after traversing an untroubled sea
The waves resulting from distant storms may become organized into swells through assimilation as faster waves overtake slower ones and larger waves superimpose themselves on smaller ones. Such wave trains can travel thousands of miles before they reach shore. In the open ocean they lie low and wide without creating much resistance or disruption. Nevertheless they are powerfully endowed with energy.
Swells rolling in on Halibut point
Swells begin to rise when the bottom of their water column encounters solid land. Even if their direction of travel is almost parallel to the shore rather than towards it, they pivot shoreward when the drag on their shoreward end effects a rotation on heading of the rest of the wave. As it approaches shallower water the wave is forced vertically upward. The bottom of the water column slows down as it drags over the submerged obstacle. Its upper portion surges forward until it peaks and collapses. A fortuitous breeze blowing out from the land into the face of a breaking wave may sustain it somewhat in what surfers call a "pause-hold" effect. This offshore wind puts a rooster tail of spray aloft as a complementary flourish to the crashing froth.
February dawn
The best time to appreciate the effect of wind and waves is to be standing on firm dry land when a storm passes far out to sea.

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