Climate of extremes - Antarctica: Global Science from a Frozen Continent - page 114

Box 4.2 Temperature inversions and Fata Morgana

The rapid increase of temperature just above the surface of the Antarctic results in a mirage
known as a Fata Morgana. Many people are familiar with mirages that occur on hot, sunny
days when a distant road appears to disappear in a distant lake. This mirage occurs when the
ground is much warmer than the overlying air and results in light from the blue sky being
bent as it passes through this temperature gradient. The result of this bending is that to a
distant observer the blue light from the sky appears to come from below, and is seen as a
shimmering water surface. The strong temperature inversion present over the Antarctic,
especially during the winter, results in a similar mirage, except light is bent such that light
re ected from the ground appears to be coming from the sky. The end result is that objects in

the distance appear to be stretched vertically. Early polar explorers were tormented by these
mirages as distant icebergs or other features of the distant landscape appeared to be looming
ice palaces or cities. The appearance of these floating cities gave rise to the name Fata

Morgana, which is Italian and relates to the fairy Morgan in the tales of King Arthur. In these
tales the fairy was able to create castles in the air similar to the ice cities seen by early polar
explorers.

Figure 4.11 Photograph of a Fata Morgana, a complex mirage - the apparent cliff at the base of the

mountains - that appears lying just above the horizon and which develops in areas of strong temperature
inversions. (Credit: John Cassano)