Going with the flow: Computer tool tracks water’s changing impact in the warming Arctic

Understanding how water moves through the permafrost landscape is vital to understanding permafrost-carbon-climate feedbacks.

Almost a quarter of the ground in the Northern Hemisphere is permafrost. This frozen ground supports critical energy infrastructure and unique ecosystems, and it also serves as one of the largest land-based stores of organic carbon matter on Earth. Across the world, permafrost traps 1,300 billion tons of carbon, or twice as much carbon as what’s in our atmosphere.

Permafrost is thawing as global temperatures rise, driving rapid change and unanticipated dangers in and beyond the Arctic. Immediate impacts include the recent collapse of the Norilsk oil storage facility, which caused a massive oil spill into the Ambarnaya River near the Arctic ocean in Russia. Less obvious, but with global impact, is the growing amount of carbon dioxide and methane released through the thawing and decomposition of this huge permafrost carbon store.

These increasing emissions can serve to increase the heat trapped by the greenhouse effect, which in turn can lead to more thawing. While not fully understood, this feedback loop is one of the more well-known and worrying potential climate change outcomes. Current models that do not yet include the permafrost-thaw feedback indicate that for each degree Celsius that the global temperature rises, one million square miles of permafrost will thaw. Adding in the extra emissions from permafrost thaw could mean the geographic extent of thaw per degree Celsius may be much worse. Recent research into phenomena like abrupt permafrost thaw suggests that our estimates for CO2 released from thawing permafrost may need to increase by as much as 50 percent.

Understanding how water moves through the permafrost landscape is vital to understanding permafrost-carbon-climate feedbacks. Water carries nutrients; it carries energy. It can increase not only the rate of permafrost thaw, but the carbon dioxide and methane output, too. To understand the impact of these hydrologic feedbacks, Los Alamos National Laboratory, with collaborators from Oak Ridge National Laboratory in Tennessee, led the development of a new open-source simulation tool called Amanzi-ATS.

Amanzi means “water” in Zulu. Amanzi-ATS looks at how water flows on the surface and below in specific environments. The software uses information such as topography, vegetation makeup, soil type, and bedrock depth to digitally simulate an area. Then, for example, Amanzi-ATS replicates a rainstorm, mapping how water runs over the land and flows through various layers underground.

In cases with ample historical data, like geological surveys, Amanzi-ATS enables researchers to tailor new simulations to a new location in as little as a few days. In lesser studied regions, like the Arctic, where permafrost research is relatively young, limited data makes the modeling more difficult. On top of that, the extreme complexity of permafrost environments makes the task even more challenging — a challenge that Amanzi-ATS overcomes.

For instance, in Utqiagvik, Alaska, the northernmost city in the United States, Los Alamos has been working with the Department of Energy Office of Science Next Generation Ecosystem Experiment — Arctic project to study the collapse of ice wedge polygons — straight-sided, odd-shaped land forms bounded by frozen wedges of underground ice that have been growing slowly over thousands of years.

From high above, these polygons create a lizard-skin pattern where the raised edges trap pools of water in their centers. But as the ice wedges melt, the raised edges sink. Troughs form around the centers, potentially creating large-scale drainage networks as the polygons disappear. As this transformation is happening, the water begins to flow over this land in unexpected ways, and that’s where Amanzi-ATS is revealing troubling insights.

Previously, researchers thought permafrost would thaw slowly as higher temperatures penetrated the earth. But moving water quickens thawing, so understanding that movement of water through and over the ground is very important.

When polygons thaw, some areas will dry out, causing vegetation to die off, which means the ground will store less carbon. Where water pools without draining, CO²-emitting microbes will die. But those conditions suddenly become ideal for single-celled organisms that release methane into the atmosphere, which is 86 times more potent as a greenhouse gas than carbon dioxide.

Water is becoming an increasingly valuable resource, so understanding its path through the world is more important than ever in areas far beyond the Arctic. Amanzi-ATS can help us understand how forest fires are altering water flow in mountains, the regional impacts of changing precipitation patterns, and how sea level rise and extreme droughts will affect the surface and groundwater resources cities depend upon.

The predictions enabled by Amanzi-ATS can help society prepare for the changing future. Ideally, if we can understand what that future holds, we can contribute to the best outcomes.

David Moulton is the deputy group leader of the Appli

ed Mathematics and Plasma Physics group at Los Alamos National Laboratory, where he leads development of algorithms and open-source software for environmental applications.

This story first appeared in the Santa Fe New Mexican

Breaking stories from Los Alamos National Lab, a multidisciplinary research institution engaged in strategic science on behalf of national security.