Decade of EROS research offers broad insight into Alaska permafrost, land change

Map of Alaska land change

Permafrost, water flow and land cover change are huge topics in Alaska, and with good reason.

Climate change hits the Arctic at twice the rate of the lower 48 states, and the ripple effects of rising temperatures, shifting water channels, wildfires and thawing permafrost are tangible and direct.

Roads wash out and buckle. Houses sink. Pipelines are stressed. Spruce-filled forests burn and give way to birch, disrupting ecosystems and forcing species to adapt or move along.

The Arctic is also a massive repository of stored carbon, the release of which carries the potential for impact far beyond its northern and southern confines.

Of all the work done to map change in Alaska, some of the broadest has come from the remote-sensing specialists at the Earth Resources Observation and Science Center (EROS) near Sioux Falls, SD.

Over the past decade, scientists at EROS have combined satellite and other remote sensing observations with field data to produce or contribute to statewide assessments of carbon potential and near-surface permafrost. They’ve also refined measurement techniques, combing electromagnetic resistivity data for clues on permafrost depth.

The latest project, led by USGS Scientist Bruce Wylie and SGT contractor Neal Pastick, is perhaps the widest look yet at the past, present, and future of the land they call the Last Frontier.

Their study, being published in the Global Change Biology Journal, was part of a partnership across numerous federal agencies that aimed to measure ecosystem susceptibility to disturbances.

The researchers used Landsat and climate reanalysis data to catalog and map land and surface water changes across all of Alaska between 1984 and 2015. It’s the first study to map the entire state at 30-meter resolution, matching the resolution of the Landsat data held at EROS and freely available to the public.

Physical Scientist Neal Pastick investigating erosion along Alaska’s Arctic coastline near the village of Kaktovik.

Statewide report can serve as ‘baseline’

Alaska’s experts can use the research as a baseline for the state, allowing them to see how wildlife, infrastructure, and land management decisions play into the statewide picture.

“These are things that people have known about and reported on for some sections of Alaska, but I think the value of their work is that they processed the information for the entire state,” said Professor David McGuire of the University of Fairbanks, who led the previous work on Land Carbon but was not involved in the new study. “It helps you understand the major types of change that are happening in Alaska.”

The findings are stark.

Approximately 13 percent of the state experienced major change during the three decades in question, most pointedly in the boreal regions. Changes include glacial retreat, shrub and treeline expansion, wildfires, erosion and human-led disturbances.

The full footprint of altered area is larger than the states of Rhode Island and Florida combined.

Fires were the major factor, with the residual effects still apparent 60 years afterward.

Increasing temperatures on the land and surface also played a role by influencing the flow of emergent water and opening up areas to vegetation, as well as impacting the manner in which burned areas rebound.

Surface water has increased across the state, the study found, largely due to coastal and river erosion and increasing rates of ground water discharge. The clearest changes happened in areas with the highest increase in surface temperature.

Glacial retreat opened land for new vegetation, but declines in productivity from drought stress were also observed.

Wildfire risks change, forest shifts alter ecosystems

Ultimately, the study suggests that the threat of wildfires could diminish as species such as birch move in to replace long-standing spruce.

“With those longer-term projections that look at those future land cover changes associated with fires, they show that in the long-term, there’s going to be reduced burning,” said Wylie of the USGS, who has visited Alaska annually along with Pastick and others for the past decade. “You’re going to convert the spruce forest to a birch forest, and birch doesn’t burn as often as the spruce.”

A change in fire frequency is not a simple question of good or bad. Fires can intensify permafrost melt and shift water flows, which can impact wildlife and human communities years after the burning stops.

A newly deciduous forest carries implications for foraging species, for example. Spruce offers cover for the mosses and lichens preferred by the state’s caribou populations, while birch does not.

Karen Murphy is a Science Applications Coordinator for the U.S. Fish and Wildlife Service. Questions about how lichen losses to fire will influence caribou are on the minds of land managers, as are the changing patterns of freeze, thaw and snowfall across the state.

“It’s unclear what the impact would be, but it’s definitely something that’s being looked at,” Murphy said.

Murphy has not used the findings of the Wylie study, but said large-scale mapping projects offer insight that is useful for putting local decisions in context.

“From a land manager or wildlife manager standpoint, we’re interested in cumulative effects,” Murphy said. “It’s important to have the broad-range, statewide view that a lot of these projects provide … you want to be able to understand the bigger picture.”

Modeled maps of (a) probability of near-surface permafrost (NSP), (b) presence–absence of NSP, and (c) active-layer thickness (cm) within Alaska. Oct. 2015

Infrastructure threatened by continued change

Changes to surface water through erosion and permafrost decay, meanwhile, have direct impacts on infrastructure, particularly in Alaska’s rural villages.

Newtok, a village of 350 on the western edge of the Alaska’s interior, loses 70 feet of its land a year to the Ninglick River – a pace swift enough to have inspired a request for Presidential Disaster Declaration in 2017.

The village and a handful of federal agencies have spent more than a decade crafting plans to relocate its entire population away from the swelling river and land that’s sinking as the permafrost beneath it weakens.

“They’re in danger of losing homes. Right behind those homes are a school, and in the school is the only bathing facility in the community,” said Don Antrobus, program manager for the Denali Commission’s Village Infrastructure Protection Program.

The Denali Commission’s VIP program was created two years ago to direct federal grant funding to the rural communities facing the greatest threats from erosion and land change.

A 2009 report from the Government Accountability Office identified Newtok and 30 other small communities as having the highest needs, and the Commission has used that document to define the boundaries of its work. Twelve communities were considering relocation at that point, but most had made little progress.

The Commission’s projects run the gamut of infrastructure assistance, Antrobus said, from massive undertakings like the one underway in Newtok to grants that help communities protect fuel facilities or develop hazard mitigation and emergency response plans.

In a rapidly-changing state, Antrobus said, data defining that change is crucial. The 2009 report is almost a decade old, and only looks at erosion threats.

The VIP is currently working with the Army Corps of Engineers and the University of Alaska-Fairbanks on a new assessment that will factor flooding dangers and permafrost degradation to the mix of rural infrastructure risks.

Any research that contributes to the understanding of change is valuable in the creation of those assessments, he said.

“All of this work is based on existing, available data,” Antrobus said. “The better information we have, the better the product becomes.”

More research needed to understand Alaska

Wylie sees the most recent contribution to Alaska land change research as an extension of previous EROS-aided work on land carbon potential and permafrost thaw. Its accuracy was bolstered by methods fine-tuned through remote sensing research published in 2013, based on field work in the Yukon Flats.

As with most research, the new study “results in more questions than it answers,” he said, adding “there’s fodder for more work.”

The study suggests that enhanced monitoring will be necessary for researchers to keep pace with the rapid changes in the Arctic.

Findings that place climate-enhanced vegetation growth alongside the vegetation-limiting effects of increased evaporation and drought square with previously-completed research, SGT’s Pastick said, and offer further evidence that a watchful eye is key to understanding the changing Arctic.

The land change study “demonstrates that northern high latitudes are not responding in a simple linear fashion to increased temperatures and growing season lengths,” Pastick said.