Howling High Arctic Winds and Hard Rime

As a CANDAC CREATE intern, I’ve been lucky enough to spend part of my summer in beautiful Eureka, Nunavut working at PEARL as an Assistant Operator. Having never been north of the tree line, I was eagerly awaiting whatever uncommon experiences lay in store for an Arctic summer.

Soon after my arrival in late June, there were a couple days when the weather was unseasonably inclement – even by Arctic standards – leading to a rather unique opportunity for weather observation at PEARL. While temperatures at the Eureka Weather Station hovered around 0°C, the unrelenting northerly winds blew consistently over 50 km/h with gusts up to 83 km/h, making it feel a whole lot colder out on the tundra. 610 m above sea level, the PEARL Ridge Lab was engulfed by cloud. At this height, temperatures were colder and the wind was fiercer. With the addition of driving snow and ice, making it difficult to see, working safely and effectively on the exposed rooftop was impossible.

When weather conditions cleared up the next day, Pierre (the PEARL site manager) and I went up to the rooftop observing platform to assess the aftermath. We found a veritable icescape that left no doubt as to the direction and intensity of the previous day’s high winds. On the windward surfaces of the perimeter railings, support posts, and many of the instruments themselves, frosty protuberances jutted out horizontally as much as 25 centimeters. These frost formations had a granular appearance with crystalline branches at their leading edge.

The frosty railings along the PEARL Ridge Lab roof.

The frosty railings along the PEARL Ridge Lab roof.

After consulting with Kevin Sheppard, a Meteorological Technician with Environment Canada, we confirmed that this was a variety of frost known as hard rime, typically seen at high altitudes where low-level clouds form. Kevin explained how the super-cooled water droplets that constitute a “freezing fog” cloud type freeze on contact with the cold metal surface. The accompanying high winds accelerate accretion, sometimes building up these frost formations to the point where the added weight load can become a major concern to manmade structures. Fortunately, designed as they are to endure the harsh Arctic winters, the instruments atop the Ridge Lab were mostly indifferent to this weather event.

The PEARL Ridge Lab's rooftop sun photometer, covered in frost.

The PEARL Ridge Lab’s rooftop sun photometer, covered in frost.

However, the sun photometer (pictured above) needed frost removed to restore its view of the sun, and a radio antenna wire collapsed under the weight of the thick frost and ice. The radio antenna wire (pictured below) required some reassembly and de-icing. Removing the rime revealed another layer of denser frost, still clinging to the wire in a near perfect cylinder. This initial layer was likely deposited as hoar frost, before the change in conditions brought about by the freezing fog favoured rime formation.

Cable

Frosty rooftop cable

Inner frost layer surrounding the cable.

Though this frost was remarkable, the wind speeds seen at the Ridge Lab and the Eureka Weather Station alone made this a significant weather event. While it wasn’t quite the windiest it’s ever been, gusts came quite close to the maximum for the month of June (93 km/h), and were enough to make all of the veteran station folks take notice. Located on the Slidre Fiord, Eureka is normally quite sheltered compared with most Arctic weather stations, earning it the colloquial title of “Garden Spot of the Arctic”. For these couple of days however, no one here would think that an apt description, least of all the two visiting CANDAC researchers working long days on the exposed tundra on a new Meteor Radar installation.

When the clouds parted and the winds subsided, the 24-hour sun and warmer temperatures made quick work of the remaining frost, offering hope of more temperate weeks to follow. As a first-timer in Eureka, the frigid winds and the spectacular hard rime it left on the roof of the PEARL served as a memorable introduction to summer in the High Arctic.

– Peter McGovern

CREATE summer intern, University of Toronto

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About createarcticscience

The CREATE program for Arctic Atmospheric Science supports researchers and students across Canada. This blog provides a venue for sharing our experiences.
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