Changing climate through the ages has changed our glaciers and landscape.
The history of Glacier National Park spans thousands of years of glacial growth and recession. Approximately 20,000 years ago, the park was almost entirely encased in ice with glaciers extending out onto the plains. By approximately 11,500 years ago, Glacier National Park was nearly free of ice. The glaciers that currently reside in the park are between 4,000 and 6,500 years old and did not originally shape the park.
The current glaciers reached a maximum size at the end of the Little Ice Age around the year 1850, after an 80-year period from 1770 to 1840 that had cool, wet summers and above-average winter snowfall producing rapid growth of the glaciers. Tree ring-based climate records and historic photographs documented the initiation of glacier recession and thinning from 1860-1880. Between the years of 1917 and 1941, hot, dry summers and low winter snowpack produced rapid melting and glacial recession rates of 100 meters per year.
In Glacier National Park's boundaries, an estimated maximum of 80 glaciers existed following the era known as the Little Ice Age that ended in 1850. Today, approximately 26 glaciers remain and they continue to melt. Several years ago, the National Park Service removed signs stating the park would be glacier-free in the year 2020. Now, some forecasts predict 2030 to be the year. But what is clear though is glaciers shrink when summer melting outpaces winter snowfall, and if more snow falls in winter than melts in summer, a glacier will grow.