The closest observed lightning strikes to the North Pole occurred on June 28 and were 200 miles farther north than the storm on Aug. 10 and 11 that made headlines, a new analysis shows. The data was provided to The Washington Post by Vaisala, which operates a ground-based global lightning detection system.
The June lightning discharges were as close as 110 miles to the North Pole, according to the data. These strikes were found when, prompted by the August lightning discharges, Vaisala researchers looked back through their records to see whether there had been any lightning discharges that were even closer to the top of the Northern Hemisphere.
The answer, much to the researchers’ surprise, was yes.
According to an analysis relying on Vaisala’s GLD360 lightning detection network, there were a remarkable 19 lightning discharges between 130 and 110 miles from the North Pole over a 10-hour period on June 28, including a cloud-to-sea ice lightning strike, said Ryan Said, a Vaisala research scientist and systems engineer who helped develop the GLD360 system.
“The closest flash during this weather event was within 110 miles of the North Pole at 16:40:33 UTC — making it the closest lightning flash to the North Pole on record,” Vaisala said in a statement. “A lightning flash is defined as any discharge of atmospheric electricity (which could include either intra-cloud or cloud-to-ground strokes of lightning)."
These lightning strikes were north of 88 degrees north latitude, compared with the August lighting discharges, which were just above 85 degrees and came within about 300 miles of the North Pole.
The GLD360 system detects lightning using radio sensors around the world.
After the August Arctic thunderstorm, Vaisala examined its database to see whether there had been previous and similar lightning activity.
“What we found was so unusual we needed to investigate further to ensure everything was consistent with our data,” the company said in a statement.
Vaisala’s network began tracking global lightning activity in 2009, but the company has archives of its data going back to 2012 only. The network can distinguish between lightning discharges within clouds and those that occur between clouds and the ground.
“Looking back through our data over the last eight summers, we don’t see any previous lightning activity that was ever this close to the northernmost point on the planet,” the company said.
The lightning strikes may be another sign of a rapidly changing Arctic climate, although it’s possible that lightning that close to the pole has happened before and just not been observed.
The rarity of Arctic lightning observations prompted Said and his research team to work for two weeks to validate and visualize the data to ensure there were no errors involved. They compared the lightning data with National Oceanic and Atmospheric Administration satellite observations and found a weather system over the Arctic on June 28 that was capable of producing lightning discharges.
“Additionally, we looked at our GLD360’s sensors and each lightning flash was confirmed by at least four sensors (three is needed for validation). One lightning flash was confirmed by more than half of our sensors,” the company said in a statement.
“If we saw the lightning events from June 28, 2019, almost anywhere else on Earth, we would not have questioned their validity,” Said said. He said there is lingering uncertainty, because if the radio waves emitted by a lightning flash are too weak to be detected by at least three of Vaisala’s sensors, the detection network won’t register it.
“So, while the lightning rate in this storm was undoubtedly quite low — we only detected 19 flashes over a 10-hour time span — there may be more flashes that we did not detect,” Said said.
“Bottom line, based on our data going back to 2012, June 28, 2019, is the date of the closest lighting flash to the North Pole on record — at 110 miles. This flash was recorded much earlier and is far closer than the recent Aug. 10, 2019 detection.”
Arctic thunderstorms may be more common
The presence of thunderstorms means that the atmosphere near the North Pole was unstable enough, with sufficient warm and moist air in the lower to middle atmosphere, to give rise to them. Typically, the air is too cold and stable in that part of the world to support the ingredients needed for such storms. Said speculated that the lightning was sparked by moist, unstable air at higher altitudes that was imported from parts of the Arctic that lacked sea ice at the time, given that the air in the lowest layers of the atmosphere above sea ice is typically too stable to rise high enough into the atmosphere to form thunderstorms.
“The lifting mechanism was very likely just above cool air just above the ice,” he said in an interview.
The vast majority of Earth’s thunderstorms occur at lower latitudes, where the combination of higher temperatures and humidity more easily sparks them. However, as Alaska and other parts of the Arctic have warmed in response to human-caused global climate change, thunderstorms are starting earlier in the year and are extending to areas that didn’t used to see many such events such as Alaska’s North Slope.
According to Said, the GLD360 network detects about 2.5 billion lightning discharges each year, or about 80 discharges every second. However, only a few thunderstorms per year are detected above the Arctic Circle.
Widespread above average sea surface temperatures continue around nearly the entire Arctic Ocean. This is particularly evident in areas of open water where sea ice cover would have been found in past years.— Zack Labe (@ZLabe) August 20, 2019
[Graphic and methods from https://t.co/s3iuSDTkjo] pic.twitter.com/qSjBCZ8zNH
The near-record loss of sea ice across the Arctic in the summer has led to significantly above-average sea surface temperatures throughout the Arctic, which may be contributing to unusually warm and humid air masses — even over the remaining ice pack across the central Arctic Ocean. Alaska, for example, has seen humidity hover far above average, belying that state’s reputation for mainly cool, dry summers.
Vaisala’s detection system uses sensors that can detect the very low-frequency radio signals associated with lightning discharges more than 6,000 miles away. By combining arrival time and angle information from multiple sensors, the network can pick up greater than 80 percent of lightning strikes and pinpoint their location with a median accuracy of about a mile and a half.