OPOD - Greenland Ice Cap

OPOD - Greenland Ice Cap: A Spectacular Display of Atmospheric Optics

The Greenland Ice Cap is not only a vast expanse of frozen beauty but also a stage for mesmerizing atmospheric optics phenomena. These optical illusions are created by the interaction of sunlight with ice crystals in the atmosphere, resulting in breathtaking displays that captivate the observer. In this article, we will delve into the remarkable atmospheric optics observed over the Greenland Ice Cap, shedding light on the intricate details that make these phenomena so enchanting.

The 22° Halo: A Delicate Ring of Light

One of the captivating sights witnessed over the Greenland Ice Cap is the presence of a weak 22° halo. This ethereal ring of light encircles the sun at a distance of approximately 22 degrees. Created by the refraction and reflection of sunlight through hexagonal ice crystals suspended in the atmosphere, this optical phenomenon paints a delicate halo around the solar disc. The Greenland Ice Cap provides a pristine backdrop for this celestial spectacle, amplifying its beauty against the vast expanse of ice.

Parhelic Circle: A Whirling Dance of Light

On a brighter day, when the sun is low in the sky, another awe-inspiring display occurs over the Greenland Ice Cap - the parhelic circle. This celestial phenomenon is formed by the interaction of sunlight with diamond dust, tiny ice crystals that sparkle in the air like countless diamonds. As sunlight passes through these crystals, it is refracted and reflected, creating a circular band of light that appears to encircle the sun. The low sun angle on the Greenland Ice Cap enhances the elongated brightening on one side of the parhelic circle, adding an extra touch of magic to this already mesmerizing spectacle.

Sundogs: Celestial Twins Flanking the Sun

Among the wonders that adorn the sky over the Greenland Ice Cap are sundogs. These bright spots of light, also known as parhelia, appear on either side of the sun and mimic its position. Sundogs are created when sunlight interacts with plate-shaped ice crystals in the atmosphere. These crystals refract sunlight, causing it to split into two beams that form bright patches of light on either side of the sun. The presence of sundogs adds a symmetrical charm to the atmospheric optics over the Greenland Ice Cap, transforming the sky into a work of art.

Upper Tangent Arc: A Subtle Arch Above the Sun

If you direct your gaze above the sun while observing the Greenland Ice Cap, you may be fortunate enough to witness a weak upper tangent arc. This faint arc of light is formed by the refraction of sunlight through hexagonal plate crystals suspended in the atmosphere. The upper tangent arc appears as a gentle curve above the sun, adding an extra layer of intrigue to the atmospheric optics spectacle. Its delicate presence serves as a reminder of the intricate interplay between light and ice crystals that gives rise to these captivating phenomena.

Circumzenithal Arc: A Crown Above the Sun

Above the upper tangent arc, another celestial jewel graces the sky over the Greenland Ice Cap - the circumzenithal arc. This stunning arc appears as an upside-down rainbow positioned directly above the sun. Created by the refraction and reflection of sunlight through hexagonal plate crystals, the circumzenithal arc showcases a vivid display of colors against the backdrop of the icy expanse. Its presence adds a regal touch to the atmospheric optics panorama, elevating the visual spectacle to new heights.

The Contribution of Plate Crystals

The hexagonal plate crystals play a significant role in shaping the atmospheric optics phenomena observed over the Greenland Ice Cap. These flat ice crystals are responsible for creating sundogs, contributing to the formation of the parhelic circle, and forming the upper tangent arc. Their unique shape allows them to interact with sunlight in such a way that produces the intricate patterns and phenomena that adorn the sky. The abundance of plate crystals in the atmosphere above the Greenland Ice Cap ensures a rich tapestry of atmospheric optics, providing a visual feast for those fortunate enough to witness it.

In conclusion, the Greenland Ice Cap is not only a majestic natural wonder but also a stage for an extraordinary display of atmospheric optics. From the delicate 22° halo to the whirling parhelic circle, and from the celestial twins of sundogs to the subtle arcs above the sun, the Greenland Ice Cap offers a visual symphony of light and ice crystals. These phenomena serve as a reminder of the wonders that nature can create, captivating and inspiring all who have the privilege to witness them. So, if you find yourself standing on the vast expanse of the Greenland Ice Cap, remember to look up and embrace the breathtaking dance of light that unfolds above you.

Greenland Ice Cap

A weak 22° halo shines over the windswept wastes of the Greenland Ice Cap. Imaged by Ed Stockard (photostream) 4th October -25C at Summit Station 72°35'N 38°25'W 15,530 ft above mean sea level. The ice beneath the station is nearly two miles thick.

©Ed Stockard, shown with permission.

1st October, a brighter and less windy day. Diamond dust and a low sun spin a parhelic circle around the sky. The elongated brightening on the right is a 120° parhelion.

Above the sun a weak upper tangent arc. Above that a circumzenithal arc from hexagonal plate crystals.

Plate crystals have created the two sundogs and contributed to the parhelic circle.

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Reference Atmospheric Optics

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  • "OPOD - Greenland Ice Cap". Atmospheric Optics. Accessed on March 28, 2024. https://atoptics.co.uk/blog/opod-greenland-ice-cap/.

  • "OPOD - Greenland Ice Cap". Atmospheric Optics, https://atoptics.co.uk/blog/opod-greenland-ice-cap/. Accessed 28 March, 2024

  • OPOD - Greenland Ice Cap. Atmospheric Optics. Retrieved from https://atoptics.co.uk/blog/opod-greenland-ice-cap/.