By Jenny Neyman
In assessing the health of the Harding Ice Field, it helps to picture a savings account. Snow accumulation is like money deposited into the account, while melt drains that amount.
More snow deposited than mass withdrawn through melt would mean the account grows. More melt than snow results in a shrinking balance, while snow accumulation equal to melt creates stability.
Just like bank accounts, glaciers can benefit from factors that act like interest to boost the balance. For instance, having the bulk of a glacier at higher elevations, with a limited amount of slope exposed to warmer temperatures below, reduces melt. But bank fees and service charges — those pesky factors that exacerbate depletion — also have an impact. If a glacier terminates in a lake or at tidewater, its rate of loss will be accelerated.
The Harding Ice Field, today covering over 700 square miles of the Kenai Mountains, has weathered many booms and busts in ice-adding and melting conditions since it formed more than 23,000 years ago, during the Pleistocene Epoch. Yet its continued survival, under the current and continuing trend of conditions, appears a less and less bankable certainty.
“The ice field essentially is thinning in almost all places,” said Dr. Martin Truffer, from the University of Alaska Fairbanks.
In some spots, the thinning has been measured at minus 3.5 meters annually.
“That’s about 10 to 12 feet of elevation change per year — about the size of this room of elevation drop every year, averaged over the last 50 years. These are really large changes,” Truffer told an audience assembled in the Seward Library Community Room on July 22 to hear an update of a project to measure the thickness of the Harding Ice Field.
Studies so far indicate a chilling future for the more than 30 glaciers radiating from the ice field along the eastern spine the Kenai Peninsula, but not yet assured bankruptcy of the field itself. There are still signs of health — primarily that each winter’s snow on the top of the ice field doesn’t all melt come the following fall.
“If you start seeing a lot of exposed ice on the ice field itself at higher elevations, then that’s bad because that means it’s going to thin and it’s going to increase thinning over time. … If the ice field still has snow from last winter then, for the moment, the ice field is still OK,” he said.
Truffer, a physics professor with the Glaciers Group at the Geophysical Institute at UAF, conducted a ground-based radio wave survey of the ice field around Exit Glacier in 2010 as part of a project funded by the National Park Service, and is continuing annual laser aerial measurements with funding from NASA.
This is Truffer’s first opportunity to study the Harding Ice Field, he said, following his glacier research elsewhere in Alaska, in Greenland and Antarctica. The Harding is an interesting chunk of ice, though perhaps not at first glance. It’s not the biggest ice field in Alaska — that would be the Bagley Ice Field in Southeast Alaska, at 127 miles long and six miles wide. But it is the largest ice field contained entirely within the U.S., as the larger fields in Southeast are shared with Canada. The Harding also is unique in that it lies entirely within federally protected lands. And most interestingly to Truffer, it contains a variety of glaciers.
“Basically any type of glacier that exists in the world exists here in this ice field,” he said.