Polar Stratospheric Clouds Over Iceland

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Over the last couple of days, we’ve been treated to a rare and beautiful sight here in Reykjavík, Iceland. Polar stratospheric clouds have been spotted in the sky, radiating like flying unicorns in shimmering, rainbow-coloured hues. I captured video of this otherworldly sight from the lounge room of my apartment at 11:33am this morning, Monday 28th December 2020.

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What is a Polar Stratospheric Cloud?

In Icelandic, polar stratospheric clouds are called glitský, which translates roughly to mean ‘glitter cloud’. What makes them so special to witness is that they are even more elusive than the Aurora Borealis. These high altitude clouds form at around 15 to 25 kilometres above sea level in the stratosphere. The stratosphere is the second layer of the Earth’s atmosphere and is also the region that contains the ozone layer.

Types of Polar Stratospheric Clouds

There are two types of polar stratospheric clouds: Type I clouds are composed of nitric acid, water and may sometimes contain sulphuric acid. They typically form at around −78°C (−108°F). On the other hand, Type II clouds consist only of ice crystals. They form when the temperature drops below −88°C (−126°F).

Type II ice clouds are often clearly visible from the ground as colourful nacreous mother-of-pearl clouds, while Type I nitric acid clouds are iridescent under certain conditions and usually only visible during twilight, when they appear as a thin haze.

Polar Stratospheric Clouds and Ozone Depletion

Scientists have known for a long time now that Type I polar stratospheric clouds play a role in Antarctic ozone destruction. Recently, they’ve discovered that these clouds are also occurring at an increasing rate in the Arctic. According to NASA, the atmosphere above the Arctic has been colder than usual over the past few years. While polar stratospheric clouds usually occur during winter, they’ve since been observed forming late into spring with associated decreasing ozone levels in the Northern Hemisphere.

Gradual thinning of the ozone layer, known as ‘ozone depletion’, poses a significant risk to all life on Earth. One of the main consequences of ozone layer depletion is increased UV radiation reaching the Earth’s surface, which can lead to a range of biological effects on human health including increased rates of sunburn, skin cancer and cataracts. Animals are also susceptible to epidermal sun damage.

Ongoing Research into Polar Stratospheric Clouds

In the Southern Hemisphere, from the Australian Antarctic base at Davis Station, the Australian Antarctic Program conducts valuable research into polar stratospheric clouds using the Davis LIDAR. This remote sensing instrument has been operating since 2001, recording information on atmospheric density, temperature and wind velocity as a function of altitude. These measurements are used by scientists to investigate the climatology of polar stratospheric clouds, their relation to the temperature of the stratosphere, as well as their effect on ozone depletion.

So, while these clouds are beautiful to witness, they may be an indication of something more sinister happening up there in the Earth’s atmosphere. If you ever happen to see polar stratospheric clouds in the sky, it’s worthwhile reporting the sighting to your local climate service. You could potentially assist them in collating data for further research.