Arapaho Glacier in Colorado, photographed in 1917 by W.I. Hutchinson (courtesy  National Snow and Ice Data Center ).

Arapaho Glacier in Colorado, photographed in 1917 by W.I. Hutchinson (courtesy National Snow and Ice Data Center).

Arapaho Glacier in Colorado, photographed in 2004 by Jon Van de Grift.

Arapaho Glacier in Colorado, photographed in 2004 by Jon Van de Grift.

Glacier recession observed through repeat photography

Repeat photography is a powerful observational tool for understanding the impacts of climate change. Here, the Arapaho Glacier, the largest on the Colorado Front Range, has experienced a significant loss in its mass balance in less than a century, as evidenced by W.I. Hutchinson’s photograph captured in 1917, and my recapture of the same scene in 2004. Geologically, this is no longer a glacier because it is only recessional, meaning it is receding in most years. This perennial snowfield is an important part of the Boulder, Colorado watershed.