Whitecaps on Bark Lake

November 26, 2011


PhotographerMary Brown
Summary Author: Mary Brown; Jim Foster

The above photo showing whitecaps on Bark Lake, Ontario was taken on June 1, 2011. This scenic lake was whipped up by winds that gusted over 50 mph (43 knots). When a light breeze blows across a still lake, capillary waves will initially appear. If the winds persist, gravity waves (ordinary lake waves) will then develop. If the wind becomes stronger, greater than about 15 mph (13 knots), whitecaps will form. In essence, whitecaps are simply breaking waves -- a myriad air bubbles gives them their familiar white cap. The breaking wave allows the wind to “grip” onto a larger surface area than a wave without such a frothy cap, giving the potential for forming higher waves. Because Bark Lake is about 9 mi (14 km) across, its fetch, distance of water the wind blows across, is limited. Thus even in storms that generate winds in excess of 75 mph (65 knots) waves won’t attain heights found in the open ocean. On a lake having a fetch of about 10 mi (9 nautical miles), winds blowing at 40 mph (35 knots) for days on end won’t create waves higher than about 7 ft (2.1 m).

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot S5 IS; Focal Length: 16.4mm; Aperture: f/4.0; Exposure Time: 0.0010 s (1/1000); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: Adobe Photoshop CS3 Windows.