Mirages observed at Tuktoyaktuk, Northwest Territories, Canada on 16 May 1979

 

The following photographs present mirages photographed in the early morning hours of 16 May 1979. Permission is granted to use these images for further research and/or publication, on condition that the source is clearly acknowledged.

 

Shortly before these images were recorded, the Novaya Zemlya effect (a premature return of the midnight sun) had been observed and photographed. This has been reported in some detail in a paper by Lehn and German. The effect is caused by an optical duct in the atmosphere, created by a well defined surface layer of cold air that lies below distinctly warmer air. The duct captured nearly horizontal light rays and transmitted them around the curve of the Earth. The duct also produced the terrestrial mirages shown below, in which objects are extremely distorted, often beyond recognition. The duct itself is visible as a grayish band resting on the horizon. The mirages appear within this band.

The landscape in the photographs is the Mackenzie River delta, where the river flows into the Beaufort Sea. The land has a low profile, with elevations generally not exceeding 30 m above sea level. One of the dominant features is a great profusion of pingos; a pingo is a low rounded hill, usually covered with detritus and scrub vegetation, whose core is a flattish lens of ice left over from the last Ice Age. The example shown here has a peak elevation under 20 m.


At the time of the observations, the sky was clear, the wind calm, the atmospheric pressure 101.0 kP, and the surface temperature about 2 C.


The coordinates of the observation point were  69 2618˝ N, 133 0220˝ W. This point is marked on the map. Also shown is the Due North line passing through this point, relative to which the true bearings of lines of sight can be measured. The map itself is a portion of the standard 1:250000 sheet entitled "Mackenzie Delta, Map 107C, Energy Mines and Resources Canada." It is available from the Canadian Government website http://www.geogratis.cgdi.gc.ca/.



Details of the photography:

The images were captured on Kodachrome 64 film. On the camera was a 560 mm f/6.8 lens, positioned at an elevation of 2.5 m above sea ice level. Typical exposure was 1/15 sec at f/6.8. All lines of sight passed across the frozen Beaufort Sea.

The images are full frame scans, 2700 x 1800 pixels. An angular scale has been inserted near the left edge of each image; it represents 10 arcminutes.

 

Click on an image to see the full-sized version. The images are arranged according to bearing angle.