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Alaska’s Glaciers and Climate Change

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Glaciers are dynamic.  Over time, they advance or retreat depending on climatic conditions.  They form, and spread, when more snow accumulates in the winter than melts in the summer. Since the end of the Little Ice Age in the mid-1800s, most glaciers have been either stable or in slow retreat.  In the last half century, however, that rate of retreat has increased.

This summer, I had the opportunity to travel around Alaska. While there, I visited a few of its nearly one hundred thousand glaciers and learned more about how they are responding to climate change.

According to the U.S. Fish and Wildlife Service,  Alaska’s  statewide  glacial  mass  balance – the net gain or loss of ice – has been negative since the middle of the 20th century.  While conditions at individual glaciers vary, the majority are melting. Recognizing that natural variables like the Pacific Decadal Oscillation (PDO) and El Nino Southern Oscillation (ENSO) have always affected Alaska’s glaciers, most scientists agree that human-caused global warming has accelerated glacial retreat across the state.   Earth’s average temperature increased 1.4°F in the last century, but Alaska is warming even faster.  The E.P.A. reports that Alaska’s average temperature has increased 3.4°F in the past fifty years with winters warming by an average of 6.3°F.  These warmer temperatures coupled with shifting precipitation patterns are causing glaciers to both shrink in length and thin in volume.

A striking visual example to this process is Exit Glacier in Kenai Fjords National Park. It is one of forty glaciers in the park that flow out of the Harding Ice Field, but is the only one easily accessible by foot. As such, the trail leading up to it is marked with signs that point out the glacier’s previous extent and progressive retreat over nearly two hundred years. The first sign, 1815, is now over one and a half miles from the current terminus.  According to the National Park Service, this glacier has been receding at a rate of forty three feet per year, on average.  Between September 2011 and October 2012, however, it retreated one hundred thirty three feet.

While shrinking glaciers in Alaska may seem like a remote environmental issue, they have far reaching impacts. A recent study by NASA and the University of Alaska – Fairbanks found that the state’s melting glaciers are one of the largest contributors to rising global sea levels.

Exit Glacier with melt water running off into the outwash plain. Image Credit: The Weather Gamut

Exit Glacier with melt water running off into the outwash plain.                                                  Image Credit: The Weather Gamut

Sign along the Exit Glacier trail that marks the location of the terminus in 1926. The glacier's current position is visible in the background. Image Credit: The Weather Gamut

Sign along the Exit Glacier trail that marks the location of the terminus in 1926. The glacier’s current position is visible in the background behind the trees.                                                       Image Credit: The Weather Gamut

The progressive retreat of Exit Glacier in Kenai Fjords National Park, Alaska.

Mapping the progressive retreat of Exit Glacier in Kenai Fjords National Park, Alaska.                     Image Credit: NPS

Denali’s Wood Frogs Freeze for the Winter

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While traveling in Alaska recently, I had the opportunity to visit Denali National Park and Preserve.  Its landscape, which includes Mt. McKinley – the highest mountain in North America – and its diverse wildlife were nothing short of impressive.  However, it was the tiny wood frog – the park’s only amphibian – that peaked my curiosity when I learned how it survives the region’s subarctic winters.

Situated at roughly 63°N latitude, winters in Denali are long and extremely cold.  From October to March, temperatures can range from 20°F to as low as -40°F.  These cold conditions drive many creatures to hibernate in dens or migrate south. The wood frog, however, makes it through winter by burrowing into leaf litter and literally freezing solid until spring.

According to wildlife biologists, a wood frog responds to falling temperatures by converting glycogen in its liver into glucose (sugar) and pumping it throughout its body.  Acting like a natural anti-freeze, the glucose lowers the freezing point of water inside the frog and protects its tissues and organs.  As temperatures continue to drop, however, the frog does eventually freeze.

Throughout the winter, the frog is essentially lifeless.  Its heart stops beating and it does not breathe.  Yet, as temperatures rise in spring, the frog thaws and comes back to life. While scientists are not exactly sure how this amazing resurrection works, they have noted that the wood frog’s heart and liver freeze last and thaw first.

Although the wood frog can be found across North America, the Alaskan wood frog is known to endure colder temperatures and freeze for longer periods of time than its southern cousins.  It is also the only frog found north of the Arctic Circle.

woodfrog

Wood Frog

Image Credit: NPS

Record Heat in Alaska

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Extreme heat is baking Alaska. In fact, some parts of this subarctic state were as warm or warmer than Miami, FL this week.

According the National Weather Service, the temperature in Talkeetna, AK reached a sweltering 96°F on Monday, smashing the previous record of 91°F set in 1969. Cordova and Valdez, each reported readings of 90°F.  In Anchorage, the mercury only made it to 81°F on Tuesday, but it was still enough to break a daily record that was in place since 1926. The average high for this time of year in south-central Alaska is in the mid-60s.

This unusual heat was the result of a strong ridge of high-pressure locked in place over the region for the past few days.  These soaring temperatures, however, are not likely to last much longer.  Forecasters expect conditions to cool down by the end of the week.