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Weather Almanac for February 2002
NORTH AMERICA'S RECORD COLD
As I write this February Almanac (mid-January), most of North America south of the Arctic Circle has enjoyed a rather mild winter. Yes, colder than normal temperatures have visited some areas, and Buffalo, New York was buried under 7-plus feet of snow when a week of cold air intruded on the holiday season, but, for the most part, we have yet to see the widespread cold temperatures common to this season. Indeed, the unusual warmth in Canada's capital city Ottawa has delayed the opening of the Rideau Canal skateway (a 7.8 km (4.9 mile) long skating path used by over a million skaters each year). Many early winter festivals in the eastern US and Canada have been scrambling to adjust to little snow on the ground and thin ice.
Such high profile news gives credence to those warning of global warming. But if we step back just over half a century to 1947, we can find an event that surely strengthened the then widely held belief of many climatologists that the next ice age was around the corner. That event has been listed by many, many web pages and reference books: the coldest temperature ever officially measured in North America.
The record books/pages generally give it one line:
Coldest Temperature (North America): -81.4 oF/-63 oC, Snag, Yukon, Canada, February 3, 1947
The full story, however, runs deeper than this sterile line. This essay and an accompanying one, give, as Paul Harvey would say, "the rest of the story."
Snag, Yukon Territory, Canada
In 1947, the village of Snag boasted a population of 8 to 10 natives and fur traders. An additional staff of 15-20 airport personnel meteorologists, radio operators, aircraft maintenance men lived at the airport barracks.
The native village was named Snag during the Klondike Gold Rush because the milky waters of the White River and its tributaries such as Snag Creek were difficult for boatmen to read. Many boats became "snagged," and often punctured, on submerged tree trunks hidden in the shallow waters.
Snag's Unique Climate
Snag is located in a bowl-shaped valley of the White River, a tributary of the mighty Yukon River, which flows northward from the Wrangell Mountains near Mt Churchill. (The Wrangell Mountains are located west of the St Elias range which includes Mt Logan, Canada's highest peak.) The village is about 30 km (18 miles) east of the Alaska border and 25 km (15 miles) north of the Alaska Highway marker Mile 1178. The St Elias mountains rise 50 kilometres (30 miles) to the south. The local vegetation on the unglaciated uplands is mostly scrub and poplar trees less than 6 m (20 ft) tall.
The Snag region has a unique climate. With the Wrangell, St Elias and Chugach Mountain ranges forming a high barrier along the coast, the flow of milder Pacific air into the region is effectively blocked. This leaves the region open to the cold frigid air masses of the western arctic. Additionally, the broad valley terrain surrounding Snag allows cold air to drain down the slopes and river valley from the north slopes of the coastal mountains and accumulate in low areas.
Snag's climate in winter thus resembles eastern Siberia, one of the coldest places on earth. Winters are prolonged and characterized by bitter cold temperatures, generally clear skies and calm or light winds. January in Snag sees average daily maximum temperatures at a chilling minus 13.2 oF (minus 25.1 oC), and average daily minimum temperatures at a frigid minus 32.1 oF (minus 35.6 oC), and the thermometer regularly dips below minus 58 oF (minus 50 oC).
The cold air drainage and formation of thick temperature inversions under light winds form ideal conditions for extreme low temperatures.
A Cold Season – 1946-47
North America's cold extreme was not an isolated event in either time or space. Extreme cold conditions were the norm over Alaska and northwestern Canada for much of the Winter of 1946-47. A new low-temperature record for the Yukon had been set 13 December 1946 at Mayo, 260 km (163 miles) by air northeast of Snag, when a numbing minus 72 oF (minus 57.8 oC) was recorded. (In this essay, I am sticking to degrees Fahrenheit as the prime unit of temperature measure since that was the standard for all of North America at the time. The equivalent Celsius reading will be given in parentheses.)
Meteorologists attributed the extended cold weather to a strong zonal (westerly) circulation in the upper atmosphere across North America that trapped arctic air over Alaska and northwestern Canada for much of the winter. This built a cold dome of intensely frigid air over the Yukon. The air mass, which spilled into northern British Columbia, the Northwest Territories and eastern Alaska, reached its coldest during a period beginning about January 27 and lasting until 4 February. Many sites set record cold temperatures for January and February that still stand. For example, British Columbia's all-time officially recorded low temperature descended on Smith River on 31 January: minus 74 oF (minus 58.9 oC).
As the cold, heavy air mass lingered over the Yukon, its coldest air settled near the surface and drained into low-lying valleys. As February dawned, the weather observers at Snag reported clear skies and calm winds ideal conditions for extremely cold temperature readings with patches of ice fog. Temperatures during the night nearly slid off scale and during the day rose no higher than minus 50 oF (minus 45.6 oC).
Few dared venture forth on Groundhog Day (2 February) to look for shadows as the morning temperature dropped to the last mark on the standard alcohol minimum thermometer: minus 80 oF (minus 62.2 oC), a new record low for the continent. [In regions where extreme cold temperatures may occur, the thermometers used are alcohol-based rather than mercury-filled. Mercury freezes at about minus 39 oF/oC.] By 2 pm (YST), the temperature had risen to only minus 51 oF (minus 46.1 oC). Shortly after the day's temperature peak, the alcohol dropped rapidly over the succeeding five hours and then declined slowly through the night.
Weather officer-in-charge Gordon M. Toole kept vigil on the minimum thermometer that night. As he hurried from the log barracks to the instrument shelter some thirty metres away, Toole could feel the cold invade his parka. He recalled clearly hearing dogs barking in the distant village and a tinkling as his breath, frozen instantly in the cold, fell as a white powder to the ground below.
Shortly after 7 am on the morning of 3 February 1947, Toole cautiously opened the instrument shelter door, taking care not to breath on the instruments inside. Using his flashlight to illuminate the minimum thermometer, he saw that the sliding scale within the alcohol column (used to register the minimum temperature) was below the lowest scale marking: minus 80 oF ( minus 62.2 oC).
Toole quickly returned to the barracks and convinced a colleague to come out and witness the mark. Using a set of dividers to determine the slide's position below the minus 80 mark, Toole estimated the reading of about minus 83 oF ( minus 63.9 oC). The previous record low had lasted but one day!
Scientists at the head office of Canada's weather service had anticipated the possibility of a temperature reading under minus 80 oF. Therefore, they had recommended in such a situation that the weather observer mark the lowest level with a pen and then send the thermometer to Toronto for determination of the temperature. Toole found a pen would not work under such cold temperatures and used a small file to etch a mark in the glass.
Accounts of events recalled fifty years later differ as to the reaction of staff at the time of the event. Toole recalls no real interest, but according to weather observer Wilf Blezard (in an interview with reporter Greg Ralston of the Yukon News in 1997): "We had to put a lock on the door of the instrument screen because everyone was rushing out and looking at the thermometers...."
On the record-setting day, the morning observation reported a surface pressure of 1037 mb, calm winds and visibility of 32 km (20 miles). In some directions, visibility was reduced by patches of ice fog, most noticeably over the area where a dog-team was hitched. The snow on the ground measured 38 cm (15 inches) but, due to the intense dryness of the air, was decreasing at a rate of about 1.3 cm (a half an inch) per day. The record low was recorded at 720 am (YST), an hour and twenty-two minutes before sunrise. The high for the day would reach only minus 56 oF (minus 48.9 oC).
To confirm the record low temperature, the thermometer was removed and sent to the Canadian Weather Service headquarters in Toronto. Three months later after extensive testing, the temperature was officially certified at minus 81.4 oF (minus 63 oC), a new record for cold in North America, which still stands today.
The cold that day, however, was not solely confined to Snag. Fort Selkirk on the Yukon River, 180 km east-northeast of Snag, claimed a reading of minus 85 oF (minus 65 oC), but it could not be considered "official" because the thermometer hung on the outside wall of a building rather than being housed in a standard instrument shelter. Mayo apparently also fell to the minus 80 oF range on that historic morning, but the official temperature could not be confirmed as the weather station, its instruments and records were destroyed by fire around midnight 15 February. A surviving photograph of the instrument did show a reading around minus 80 oF, just higher than the Snag minimum. Other notable lows reported during the period are shown on the accompanying map and chart.
When news of the record cold reached the media, it made headlines around the world. The Toronto Globe and Mail declared Snag snug as mercury sags to a record -82.6o. (We'll ignore the faux pas about mercury.) Reporters from around the world sought interviews from the "frozen few" on the experience of life at minus 80. (For some of their observations, see "Life at Minus 80: The Men of Snag.")
The third of February was to be the bottom of the cold air barrel for much of the Yukon as temperatures moderated over the next few days. The westerly air current that had locked the region in an icy prison finally relaxed its grip and pushed the cold air dome out. Released from its cradle, the cold slid southeastward across the continent, bringing frost to northern Florida. Pacific maritime air replaced the arctic air, and for a few days, conditions became relatively balmy. Snag reached a peak temperature of 45 oF (7 oC) later during the month.
Since that day in 1947, several cold periods have descended on North America and the Snag region, but none have officially broken Snag's record. Prospect Creek, Alaska came close, falling to minus 79.8 oF (minus 62.1 oC) on 23 January 1971 for the American record. (However, the minus 69.7 oF (minus 56.5 oC) at Rogers Pass, Montana remains the record for the lower 48 states.) Only northeastern Siberia, interior Greenland and Antarctica have ever recorded lower official mean temperatures than Snag.
However, two locations used in a permafrost study in a mountain valley near Fort Nelson, British Columbia reached unofficial lows of minus 96 oF (minus 71.1 oC) and minus 92 oF (minus 68.9 oC). The official low recorded that day at Fort Nelson was a relatively warm minus 43.6 oF (minus 42 oC).
Given the many pocket valleys of northwestern North America, it is not surprising that the right combination of conditions could produce spot temperatures lower than minus 80 oF. Perhaps it is just a matter of time before an official climate station resides in one. After all, records are made to be broken.
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