Rocky Mountain NP glacier loss a threat to water supply

Rocky Mountain National Park’s glaciers are shrinking away.

And that’s a big problem — not only for the park’s scenic splendor, but also for Colorado communities that rely on water from the Poudre, Colorado and Big Thompson rivers, which are fed by meltwater from dozens of glaciers and glacierlike features strewn about the park.

For decades, Mother Nature has protected them from unfavorable conditions, but as the park's temperatures climb and the promise of heavy winter snowfall grows more uncertain, the park’s glaciers and glacierlike features have slowly and unsteadily started to shrink.

A single decade of prolonged drought and warm summers could spell the beginning of the end for RMNP's glaciers, according to one park ecologist. It's already happened in California, where about a decade of drought and warming temperatures have pushed Yosemite National Park’s glaciers to near extinction.

“It’s sad to say, but most mountain glaciers are predicted to be gone by the end of the century,” said Dan McGrath, a Colorado State University research scientist. “I find it hard to believe (Rocky Mountain’s glaciers) could survive given the predicted warming and likely changes in precipitation.”

RMNP glaciers have always yo-yoed in size, partially melting in summer heat and regaining mass from winter flakes. The park has 30 glaciers, according to USGS topographic maps, but some of them technically aren’t glaciers anymore. Between the 1990s and 2005, the glaciers started to shrink at an increasing rate — perhaps faster than “at any other time in the historic record,” according to a 2007 Portland State University study.

And the park’s glaciers don’t have a lot of wiggle room. Its glaciers are tiny compared to well-known glaciers in Alaska, Greenland and elsewhere. RMNP's biggest glacier is about 31 acres, the size of six Old Town Squares, and the smallest is smaller than two football fields, according to the 2007 study.

Scientists have no idea how the park’s glaciers have changed in volume over time and have only a limited record of how they’ve changed in area. McGrath wants to fix that.

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He’s conducting a two-year study to find out how the glaciers have changed in area and volume since 2005 using historic maps, climate records, photographs and present-day measurements to fill the gaps in scientific understanding of the glaciers.

McGrath and his team are focusing mostly on the well-known Andrews and Tyndall glaciers but will monitor about 10 other glaciers along the Front Range. They’ll use electromagnetic waves to measure snow accumulation and ice thickness of the glaciers. With cutting-edge laser technology, they’ll create unprecedented 3D models of the glaciers. And they’re setting up timelapse cameras near stakes planted in the glaciers to study the timing of their shrinkage.

McGrath has discovered that Andrews and Tyndall glaciers are roughly the same size they were in 2005. They grew in 2010 and 2011 because of heavy snowfall but shrunk after that.

To get a better understanding of the glaciers’ timelines, McGrath will pore over climate models to see what’s in store for temperature and precipitation in the park's higher elevations. It’s clear that warming will continue, but climate models are less certain about how precipitation will change over time in the Rocky Mountains.

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Preliminary results from an ongoing study by Glenn Patterson, a CSU geosciences Ph.D. candidate, and Steven Fassnacht, a CSU snow hydrology professor, suggest that snowfall has decreased more in the park’s higher elevations than its lower areas.

Warming temperatures will melt more of the glaciers in summer, but warming temperatures' larger impact could come in autumn and spring. A bump of a few degrees when temperatures are near the freezing point can turn snow into rain.

“Of all the things I’m worried about for glacier health, it’s that threshold,” McGrath said. “It can be 30 degrees and you get snow, or it can be 34 degrees and you might be getting only rain. That is going to dramatically alter both the behavior of the glacier and the mass balance. That’s universal.”

The final piece: McGrath’s team will study how glacier melt influences rivers, measuring streamflow and collecting water samples to see how much water glaciers contribute to rivers.

Downstream impacts are worth studying because the Colorado, Big Thompson and Poudre rivers are fed largely by snowmelt and groundwater. The park’s year-round snowfields have particularly important downstream impacts, and the snowfields behave a lot like glaciers.

Even a small loss in the snow and ice that feed Northern Colorado rivers would be a huge blow to Fort Collins and other nearby communities that rely on their water. The gradual melting of perennial snowfields bolsters late summer and fall streamflow, said Paul McLaughlin, an ecologist at the park’s Continental Divide Research Learning Center, and our water storage system depends on those established patterns. Changing water volumes and temperatures can irreparably damage delicate river ecosystems.

The strange thing about these glaciers is they shouldn’t really be here.

The park gets too warm in summer and not enough snow falls on them naturally, McGrath said. But most of the glaciers live in cirques that protect them from the summer sun, and aggressive winds shuttle snow across the Continental Divide, dumping between 5 and 10 times more snow on the glaciers than they would get from the sky alone.

“There’s something of a climate disconnect,” McLaughlin said. “In these systems where the glaciers have already retreated to these shady areas, there’s kind of a time lag in which the glaciers may persist even though the temperatures are getting warmer. But at some point in the future, we would expect they’ll reach a tipping point where they would quickly disappear.”

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That begs the question: Can, or should, anything be done to save the glaciers?

Some people advocate for man-made solutions to glacier loss, like covering them with huge reflecting blankets, sprinkling them with sawdust or pumping tons of aerosols into the atmosphere to cool them.

But McGrath isn’t a fan of messing with nature.

“It seems simple, but even a slight modification can have cascading effects downstream,” he said, referring in particular to the idea of putting slabs around Antarctic glaciers to protect them from relatively warm water.

McLaughlin said the best-case scenario for the glaciers would be a future with less greenhouse gas emissions.

“We have the opportunity as humans to manage the amount of carbon dioxide we’re producing and putting into the atmosphere,” he said. “That will have an effect on our climate moving forward, and perhaps on the lifespan of our glaciers.”

Glacier glossary

• Glacier: A slowly moving mass of ice formed from compacted snow. Glaciers generally shrink in the summer and grow in the winter, but scientists can track changes in their size over time.
• Glacierlike features: These include perennial snowfields, debris-covered glaciers and rock glaciers.
• Perennial snowfield: A mass of snow that survives the summer melting period and doesn't move much.
• Debris-covered glacier: A glacier that is largely covered by rocks, boulders and sand.
• Rock glacier: A mass of rocks with ice in between. Deformation of the ice allows rock glaciers to move. Rock glaciers are far more common than regular glaciers at Rocky Mountain National Park.

Source: Rocky Mountain National Park's"Glacier and Glacier Change" webpage