Two small icebergs are beached at low tide along the Jökulsárlón Strandur coastline in Iceland. They sparkle like diamonds on the pitch-black lava sand during the twilight of a winter morning.
The atmospheric conditions required to produce spectacular twilight colors that reveal these beached icebergs at their best are difficult to encounter during the Icelandic winter. On this occasion, the clear sky was associated with a stationary low-pressure system northeast of Iceland. The counterclockwise circulation of a cyclone drives a northward flow of warm, moist air east of its center. As this air rises, it predominantly produces cloudy weather and rain. In contrast, the western side of the cyclone is dominated by cold, dry air flowing southward. This air mass tends to descend and usually brings clear skies, sometimes interrupted by showers.
When such a cold air mass crosses Iceland from the north, however, the 1,725-meter (5,659-foot) Vatnajökull ice cap blocks its path. The air is forced to rise along the northern slopes of the ice cap, producing intense and prolonged snowfall in northern Iceland during winter. On the southern slopes, by contrast, the air descends and dries out. In the lee of Vatnajökull, this creates the characteristic clear skies of the foehn effect.
More than 20 kilometers (12.4 miles) offshore, the influence of the foehn weakens and low-level clouds can begin to form. These delicate clouds are visible along the distant horizon.
This meteorological setting created spectacular twilight light, transforming the stranded icebergs into glistening jewels on the black volcanic sand of Jökulsárlón.
