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Alaskan North Slope Climate Change Outruns Tools to Measure It

The average temperature observed at the northernmost point in the United States changed so rapidly in November that the weather station’s instruments couldn’t keep up, according to government data.

ANCHORAGE, Alaska (CN) -- The average temperature observed at the northernmost point in the United States changed so rapidly in November that the weather station’s instruments couldn’t keep up, according to government data.

When the National Oceanic and Atmospheric Administration’s Centers for Environmental Information’s climate change monitoring group went to process climate data from Utqiaġvik, Alaska – formerly known as Barrow – on Dec. 4, it was missing. This was odd, according to Deke Arndt, a climatologist with NOAA.

“[Climate data] was also missing for all of 2017 and the last few months of 2016,” Artndt wrote in a blog post on Dec. 6. “This was even weirder, because we knew we’d kinda marveled at how insanely warm the station had been for several weeks and months during 2017.”

“Utqiaġvik, as one of a precious few fairly long-term observing sites in the American Arctic, is often referenced as an embodiment of rapid Arctic change,” Arndt added.

Utqiaġvik, a town of about 4,000 residents that is now referred to by its Inupiaq name, is the nation’s northernmost community on the edge of the Arctic Ocean. It had its warmest November on record this year, with an average temperature of 17.2°F. This is 16.4°F above the 1981–2010 average, and 1.9°F warmer than the previous record in 1950, reported.

“The swift regional climate change in and near the Arctic changed so rapidly that it triggered an algorithm designed to detect artificial changes in a station’s instrumentation or environment and disqualified itself from the [center’s] Alaskan temperature analysis, leaving northern Alaska analyzed a little cooler than it really was,” Arndt wrote.

A complex mathematical algorithm, called the pairwise homogeneity algorithm or PHA test, causes data to disappear as a way of flagging weather stations that need a closer look to determine what caused such a diversion from the normal data sets.

“The PHA test is not mathematically simple, but the concept is straightforward,” Arndt explained. “When climate changes—naturally or from global warming—most of the stations in the same region should change in a similar way.”

A significant diversion in climate behavior at one weather station often indicates some kind of "artificial" change, such as moving the station from a higher, cooler elevation to a lower, warmer one, new construction nearby that blocks the wind, or swapping out a sensor.

“As a relatively isolated station, experiencing profound and unique change, Utqiaġvik was destined to get flagged. And it happened this month,” Arndt wrote. “Having built confidence that a disruption to the station was afoot, the PHA test retroactively flagged the last 16 months and removed them from the monthly analysis.”

But it wasn’t a weather station move, nearby construction or an equipment change that caused the disruption. This time, it was an actual change in climate that altered the nearby environment by reducing the amount of sea ice.

When sea ice in the region is small, warmer Arctic water is exposed to the atmosphere, which means much warmer air temperatures will be recorded at the region’s weather stations.

Arctic sea ice contracts to its smallest footprint each September and then begins advancing toward Alaska’s northern coast in October and November. In recent years, that arrival has been slower and less complete, ultimately causing the area to warm twice as fast as the contiguous U.S. over the same time period, according to data.

“In the context of a changing climate, the Arctic is changing more rapidly than the rest of the planet,” Arndt said.

Arctic communities such as Utqiaġvik are already experiencing the effects of this change, as the loss of protective sea ice allows waves and surf from fall storms to carve out swaths of coastline. A late September storm brought waves of eight feet or greater onto the North Slope coastline.

At the time, borough officials estimated $10 million in damages to roads, protective berms, sea walls and buildings, along with threats to the town’s freshwater source. Freshwater lagoons are also an important source for subsistence hunting and fishing that feed community members.

According to Arndt, he and his colleagues will be able to restore the data from measurements in Utqiaġvik over the next few months. The recent data drop will spur mathematicians to improve the PHA test, which he sees as a “silver lining.”

“Climate change is challenging.  So is measuring it. But it's important to measure it, and better data sets mean better and more confident measurements,” Arndt said.

Categories / Environment, Government, Regional

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