Anchorage Field Office installs permafrost monitoring stations along Iditarod National Historic Trail

Aliza SegalBen Stratton

BLM Anchorage Field Office staff, assisted by Geo-watersheds Scientific, recently installed two new soil temperature monitoring stations along the Iditarod National Historic Trail (INHT). The stations are located in a part of the state that previously had poor coverage from the existing permafrost and climate monitoring networks. Data from the new stations will help the Bureau understand conditions of the trail and how the trail is affecting underlying permafrost. 

Aerial shot of geotechnical station
BLM Iditarod Geotechnical Station 1 (BIG01) installed along the Iditarod National Historic Trail. Photo by Ben Stratton

The INHT is a 2,400-mile winter‐use only gold rush era trail established in the early 20th century that connects Seward and Nome via remote interior Alaska. Much of the trail travels through regions that are underlain by permafrost, often over wetlands impassable in summer conditions. Permafrost is ground that remains at or below 0° C (32° F) for at least two consecutive years and is found beneath nearly 85 percent of Alaska. Global warming has resulted in rising permafrost temperature and areas of thaw. Thawing of permafrost destabilizes the ground above it, causing soil slumping and mass wasting events. Each station measures soil temperature to approximately 3 meters below ground surface at 13 different depths. They take these 13 measurements in both the trail treadway and an adjacent undisturbed location. Additionally, they collect all climate parameters standard for a Remote Area Weather Station. 

Two men lowering a power auger into a hole.
Anchorage Field Office staff, Charles Mumford, and Geo-watershed scientific staff, George Garner, prepare the auger to drill a hole for one of the 3-meter-deep soil temperature thermistor profiles. Photo by Ben Stratton

BLM National Historic Trail Administrator, Kevin Keeler, has observed over the past decade that even though trail use is limited to wintertime travel, significant soil slumping and compaction is present, and vegetation is noticeably altered within the treadway. “These conditions may be due to permafrost degradation, loss of insulating vegetation, or other altered soil temperature regimes in the treadway of the trail,” said Keeler. 

Man using a computer under a rain shelter
Anchorage Field Office Hydrologist, Ben Stratton, configures station programming for the soil and climate sensors. Photo by Charles Mumford
Man standing next to monitoring station
Anchorage Field Office staff, Stolf Short, inspects BIG01. Photo by Ben Stratton

Data from each station are transmitted hourly via satellite telemetry and will soon be accessible on a public website, making it available to answer the questions of a wide group of researchers across Alaska and the global permafrost research community. Station data can be included in future state and global permafrost modeling updates and model validation conducted by research institutions such as the University of Alaska Fairbanks Geophysical Institute.

Man assembling an antenna
Anchorage Field Office Ecologist, Aliza Segal, assembles station equipment in the BLM Campbell Tract warehouse before deployment to the field. Deployment during summer 2020 was postponed until 2021 for COVID-19 safety precautions. Photo by Ben Stratton