March 18, 2017
By Phillip Martin
Photo Plate. (click here) Series of photographs of the terminus of Portage Glacier. 1914 and 1939 taken from Turnagain Shoulder NW to SE view; 1972 and 1984 oblique aerial view NW to SE; 1999 and 2006 oblique aerial view NE to SW toward Portage Glacier. Photo credits: 1914, Strough 1939, Barnes 1943, Plate 17B; 1972, USGS photograph; 1984, Aeromap U.S.; 1999 and 2006, USGS photographs.
When I began gardening in Fairbanks in the 1980s, (click here) killing frosts commonly occurred in August. But in recent years, I have been able to harvest well into mid-September. Climatologists tell us that Alaska is warming at twice the global average rate, and gardeners are not the only ones who have noticed. Native elders observe that natural seasonal patterns that have guided subsistence practices for centuries are no longer reliable. Glaciers popular with sightseers (Columbia, Mendenhall and Portage, for example) have receded far from their former scenic viewpoints. Seeing is believing, and perhaps that is why most Alaska residents accept climate warming as fact....
...What is perfectly clear, however, is a history of congressional inaction on the issue of climate change, and our delegation has been complicit. With so much at stake for Alaska, Sens. Lisa Murkowski and Dan Sullivan and Rep. Don Young should instead be outspoken leaders in a political alliance for sensible climate policies. These include:
• a robust multi-agency climate science program to better define risks and probable trajectories of environmental change, including a focus on arctic systems;
• vigorous support for adherence to the 2016 Paris Climate Treaty, our best opportunity to influence actions by other nations which affect us significantly; and
• strong incentives for development and adoption of energy conservation and renewable energy technologies that will reduce global carbon emissions, create new jobs and lower the staggering energy costs that currently afflict our communities and families.
We are at a critical political juncture, with Washington. D.C., politicians charting a course that threatens our economy and natural resources. Doing nothing is not without cost. It is time for Alaska’s political leaders to stop passing the buck to our children and grandchildren.
Future changes of the terminus of Portage Glacier will depend on a variety of factors. However, present scientific theory (Meier and Post, 1987, Trabant and others, 2003) suggests that calving glaciers cycle between advance and retreat patterns; with rapid retreats, followed by stable retracted positions, slow advances, and then stable extended positions that are not directly related to climate change. Thus, based on its history to date, and if such a pattern holds for Portage Glacier, the glacier may now be in its stable retracted position and could eventually begin a slow advance. However, for a glacier to advance, annual net balance—the amount of new snow and ice added to the glacier minus the amount of glacier melt—must be positive. As a rule of thumb for valley glaciers, net balance is positive when annual snow and ice accumulation occurs over more than 60–70 percent of the entire glacier area. Such accumulation occurs on the glacier above the end-of-summer snow-line altitude, recently measured by USGS at 1,000 meters in altitude. Only 50 percent (not the rule-of-thumb 60–70 percent) of Portage Glacier is more than 1,000 meters in altitude, thus, Portage Glacier may slowly thin and recede rather than experience a slow advance.
It is called the climate crisis. It is real and it is happening. Earth needs it's ice to mitigate climate and keep Earth cool.
