Brewing change in the (glacier) percolation zone
Alaska's glaciers are losing mass at the fastest rate of any region globally, significantly affecting both the volume and distribution of water across the landscape. Though glaciers in the Alaska region (as defined by glaciologists this includes both Alaska and portions of adjacent Canada) range from sea level to nearly 6200 m (20,320 ft), the majority of glacier area in the Alaska region is concentrated between 900 and 2100 m (2950 to 6890 ft). Long term glacier monitoring in Alaska by the U.S. Geological Survey (USGS) Benchmark Glacier Project is on moderate-sized glaciers with distributions of glacier area in this elevation range. These are some of the longest in-situ records of glacier mass change in the world. The process-based understanding of glacier change on those “Benchmark Glaciers” is robust, but it is limited to the range of conditions present on those particular glaciers—at moderate elevations—where large amounts of melt water and rain pass through the glacier and into the downstream ecosystem on an annual basis.