Study: Alaskan Icefield May Melt Away

The Juneau Icefield forms a snow-covered expanse in the Coast Mountains north of Juneau. This massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true, according to University of Alaska Fairbanks researchers. Courtesy: Joanna Young and University of Alaska Fairbanks.The Juneau Icefield forms a snow-covered expanse in the Coast Mountains north of Juneau. This massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true, according to University of Alaska Fairbanks researchers. Courtesy: Joanna Young and University of Alaska Fairbanks.

The massive Juneau Icefield feeding Alaska’s Mendenhall Glacier may melt by 2200 if warming predictions hold true, say researchers. The team predict that more than 60 percent of the ice will be lost by 2099 if the warming continues.

From University of Alaska Fairbanks

The massive icefield that feeds Alaska’s Mendenhall Glacier may melt by 2200 if warming trend predictions hold true, according to University of Alaska Fairbanks researchers.

The estimate is the product of the first detailed look at the future of the Juneau Icefield, source of the Mendenhall and about 140 other glaciers, said Regine Hock, a glaciologist at UAF’s Geophysical Institute.

The terminus of Mendenhall Glacier, 10 miles northwest of downtown Juneau, is visible from a U.S. Forest Service center visited by 450,000 people in 2015. If warming continues, the terminus will retreat up the valley and withdraw from view around a corner.

“By the end of this century, people will most likely not be able to see the Mendenhall Glacier anymore from the visitor’s center,” Hock said.

Hock is one of the authors on a paper published in the Journal of Glaciology that outlines their findings. UAF postdoctoral fellow Florian Ziemen, UAF glaciologist Andy Aschwanden, Hock and five others used past and present observations and mathematical models to predict how North America’s fifth-largest icefield would react under different climate scenarios.

The icefield covers 1,500 square miles in steep mountainous terrain. Climate data for the area has been sparse. The researchers were able to correct the data set from the Weather Research and Forecasting Model and combine that with the Parallel Ice Sheet Model. The Parallel Ice Sheet Model, developed by UAF researchers, is widely used by glacier researchers around the world.

The team predicted that more than 60 percent of the ice will be lost by 2099 if warming trends continue, Hock said. The entire icefield could be gone by 2200.

However, if temperatures remain the same as they are today, the Juneau Icefield will retreat only slightly and then stabilize. The researchers found interesting the model results that also show that the icefield would regrow to almost its current shape if the area were ice-free right now. That’s because the high-altitude cold weather of the mountains would cause snowfall to start the glacier-forming process again, Hock said. This is very different from other glaciers and icefields in Alaska that are at lower altitudes.

Abstract

We study the evolution of the Juneau Icefield, one of the largest icefields in North America (>3700 km2), using the Parallel Ice Sheet Model (PISM). We test two climate datasets: 20 km Weather Research and Forecasting Model (WRF) output, and data from the Scenarios Network for Alaska Planning (SNAP), derived from spatial interpolation of observations. Good agreement between simulated and observed surface mass balance was achieved only after substantially adjusting WRF precipitation to account for unresolved orographic effects, while SNAP’s climate pattern is incompatible with observations of surface mass balance. Using the WRF data forced with the RCP6.0 emission scenario, the model projects a decrease in ice volume by 58–68% and a 57–63% area loss by 2099 compared with 2010. If the modeled 2070–99 climate is held constant beyond 2099, the icefield is eliminated by 2200. With constant 1971–2010 climate, the icefield stabilizes at 86% of its present-day volume. Experiments started from an ice-free state indicate that steady-state volumes are largely independent of the initial ice volume when forced by identical scenarios of climate stabilization. Despite large projected volume losses, the complex high-mountain topography makes the Juneau Icefield less susceptible to climate warming than low-lying Alaskan icefields.

Citation

Florian A. Ziemen, Regine Hock, Andy Aschwanden, Constantine Khroulev, Christian Kienholz, Andrew Melkonian, Jing Zhang; Modeling the evolution of the Juneau Icefield between 1971 and 2100 using the Parallel Ice Sheet Model (PISM); Journal of Glaciology doi: 10.1017/jog.2016.13

Source

University of Alaska Fairbanks news release.

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