Six decades of oil field development on Alaska's North Slope, combined with climate warming, have changed the face of the land there in ways that were not expected when drilling at North America's biggest oil field began, according to a new study published online on Feb. 11 in the journal Global Change Biology.
The changes would likely be missed by a casual visitor looking at tundra today, which might appear unaffected by the passage of time, said Martha Raynolds, a research biologist at the University of Alaska Fairbanks' Institute of Arctic Biology and a lead author of the study.
The facts tell another story, Raynolds said. "The changes are very obvious when you have the before and after pictures," she said.
Among those changes: More small ponds and more areas of standing water on the tundra in summer. There is accelerated erosion of lake shores. And, of course, there are hundreds of miles of roads and acres of pads and oil-field buildings that didn't exist in the past.
Detailed aerial photographs provided much of the basis for the UAF-led study, which also incorporated permafrost data, weather data and other information.
Though it considered the entire central North Slope and its transformation since 1949, the study focused on three 20-square-kilometer sections of the sprawling Prudhoe Bay field, areas that have extensive photographic records showing the transformation from the early days of development to the present.
In those areas, 34 percent of the territory has been physically changed as of 2010 by oil-field infrastructure that sprouted up since the start of development decades ago, according to the study. That includes land directly covered by roads, well pads, airstrips, pipelines, processing facilities and other manmade structures necessary for producing oil. It also includes the areas nearby that are affected by oil facilities -- sites along roads where water puddles or floods and where vehicle-kicked dust settles, for example.
In the natural landscape away from the infrastructure, there have also been some significant changes, the UAF scientists found. Of that land, 19 percent exhibited what the scientists call "expansion of thermokarst features" between 1990 and 2001, a time of dramatic warming air temperatures. Those thermokarst features emerge when permafrost ice thaws, causing land to settle, sink or otherwise change, and sometimes fill with water, Raynolds said.
The thermokarst effects, most dramatic in the past two decades, have brought about accelerated erosion and changes in vegetation, as well as dimpling and relief changes to a previously flatter landscape, the study said. There could be far-reaching effects, it said.
"Based on the mapped information and current air and permafrost temperature trends, starting in 1990 we are witnessing landscape changes that will have major implications for much of the Arctic Coastal Plain," the study said.
The UAF-led study updates findings made in a 2003 National Research Council study evaluating cumulative environmental effects of North Slope oil development.
Back in 2003, the NRC scientists concluded that even though the Arctic climate was likely to continue warming, with impacts to Arctic sea ice and ecosystems, the North Slope's permafrost was cold and strong enough to withstand expected increases in ambient air temperature.
The UAF-led study found otherwise, Raynolds said. The warming air temperature, the influences of oil-field infrastructure, and the combination of the two have been strong enough forces to speed thawing and change surface characteristics, she said.
On another subject, however, the separate studies were in agreement.
That NRC study cited permanent roads as among the most significant oil-infrastructure features impacting the North Slope environment because of the way they disturb the natural hydrology of the tundra. That NRC study also cited road dust created by summer vehicle traffic as a chronic environmental problem.
The UAF-led study made similar conclusions, Raynolds said. The puddles and small floods created by roads total up to a large amount of territory, she said. And dust has some far-reaching effects, she said.
Light road dust can sprinkle certain nutrients onto nearby ground, encouraging some types of plants to grow and changing overall vegetation mix. The impacts of heavier dust are more dramatic, Raynolds said. "If you get large amounts of dust, it's actually smothering the vegetation," which is bad news for lichen and mosses, she said.
One important lesson from the study, Raynolds said, is that developers building on top of Arctic tundra should consider the type of permafrost below. Ice-rich permafrost, such as that at Prudhoe Bay, is more vulnerable to change, while drier permafrost is more resilient, she said.
Contact Yereth Rosen at yereth(at)alaskadispatch.com