Forecasting, Not Fearing, Sea-Level Rise

This week, the Washington Post reported a widening 80-mile crack threatening one of Antarctica’s biggest ice shelves. A large chunk of Larsen C, the most northern major ice shelf, may break off in the coming years.

Of course, the probable loss of Larsen C is a terrifying reminder that climate change is real and happening now. But what consequence will it have on Antarctic glaciers and sea-level rise? Researchers know ice shelves have a buttressing effect on interior ice because they restrain the flow of glaciers from the land to the sea. However, researchers can’t predict how the glaciers will behave once the shelf is gone.

They are getting closer, though.

I recently met with Irina Tezaur, a Principal Member of Technical Staff at Sandia National Laboratories. Her team has developed a method of understanding the hidden characteristics of land ice, so researchers can forecast sea-level rise from events like the breakup of Larsen C.

The Basics of Land Ice

Before getting into the nitty-gritty of Sandia’s work, let’s start with the basics. There are three significant ice sheets: Greenland, East Antarctic, and West Antarctic. From 1990–2012, these ice sheets lost a considerable amount of mass and contributed to rising seas. They continue to lose mass at historic levels.

Understanding and forecasting these changes are critical. Changing ice sheets will impact national security and trade. Rising seas require thoughtful adaptation measures. But the Intergovernmental Panel on Climate Change, the body tasked with assessing the risks of climate change, declined to include estimates of future sea-level rise from ice sheets in its 4th assessment report. It found there was not enough information on ice sheet behavior and dynamics.

Looking Beyond the Surface of the Ice

This is why the Department of Energy (DOE) is funding a project with several labs and universities called “Predicting Ice Sheet and Climate Evolution at Extreme Scales” (PISCEES). Sandia’s major contribution to the project is the “land-ice solver” called Albany/FELIX. It is a computer code developed by Tezaur and the team at Sandia.

The code answers what Tezaur describes as the “inverse problem” of understanding ice sheet properties. While scientists can collect measurements from the surface of ice, it’s harder to know what’s happening inside and at the bottom. How thick is it? What is the topography under the ice? What are the internal stresses, strains, and shifts it is exposed to? All of these variables are essential factors to predict ice melt, but have eluded researchers until now. Albany/FELIX inputs the factors with algorithm-derived data.

Sandia has verified the coding behind the Albany/FELIX solver, as well as validated the model’s results. Using their code, Tezaur and the team performed a validation study involving their model by simulating Greenland during the period 2003-2013 and comparing the results to observations. The study demonstrated that the team’s ice sheet model shows skill at mimicking ice sheet observations when appropriately forced, which is a significant improvement over the situation a decade ago. Validation studies such as the one performed are a necessary condition for making credible predictions of the future ice sheet state.

A code with this level of accuracy could help researchers simulate the behavior of Antarctic ice shelves like Larsen C as well as the Ross Ice Shelf — the largest ice shelf in Antarctica — in the future.

The Future of Sandia’s Work

Researchers are currently integrating the Albany/FELIX code into the larger, DOE Earth System Model. Once it is fully integrated, data from the land ice solver will build on the other atmosphere, ocean, sea ice, and land data. Researchers will have a tool to make predictions about sea-level rise more accurate and precise.

“Once our simulation code is fully integrated into the DOE Earth System Model, it will be used to simulate the evolution of the Greenland and Antarctic ice sheets during the 21st century to provide sea-level rise predictions, including uncertainty ranges, due to ice sheet mass loss caused by global climate change,” Tezaur told me. “Our hope is that these predictions will be used to inform public policy in the coming years.”

I hope the predictions inform public policy too. While I’m terrified by the news surrounding Larsen C, the promise of Sandia’s work is reassuring. As they say, knowledge is power.

However, as climate advocates in the United States have seen, science and numbers don’t always back climate change policy. Let’s hope a crack doesn’t grow between Sandia’s work and global response like it’s grown on Larsen C.