Grinnell Glacier and What Retreat Looks Like Up Close

The United States Geological Survey has been photographing Grinnell Glacier from roughly the same location, at roughly the same time of year, since the late nineteenth century. The photographs are not dramatic individually. You have to put them in sequence. The eighteen ninety photograph shows a glacier that fills the headwall of the cirque. The nineteen twenty photograph shows the same glacier, somewhat smaller. By nineteen fifty, the retreat is visible in a way that cannot be explained as normal seasonal variation. By two thousand, the comparison between the earliest and most recent photographs looks like evidence of an entirely different geological era.

The photographs hang in the visitor centers at Glacier National Park, and people stop in front of them and stand quietly for longer than they stand in front of most interpretive displays. There is something in the image sequence that a paragraph of text cannot replicate.

Grinnell Glacier is among the park's most accessible and most studied glaciers. The ten-and-a-half-mile round-trip trail from the Many Glacier trailhead, or the boat-shuttle option that cuts three miles off the approach, brings hikers to a viewpoint where the retreat is not an abstraction. The current glacier terminus sits on ground that was under significant ice when George Bird Grinnell first hiked to it in the eighteen eighties. The ground between the old terminus, marked in the geological record by moraines, and the current ice is a kind of archive: each band of newly exposed rock represents decades of warming and retreat.

The park service does not predict what the glacier will look like in ten years. The United States Geological Survey's Northern Rocky Mountain Science Center's modeling suggests the park's remaining glaciers will be mostly gone by the mid-twenty-thirties. Grinnell may go earlier; it may go later. The direction of the trend is not in question.