Coastal Mountains
The coastal mountains influence climate
The largest non-polar ice field in the world is found in the St. Elias Mountains about 200 km (120 miles) west of Golden Horn Mountain. It is the source of the Cordilleran Ice Sheet that covered Whitehorse at least six times during the last glacial age.
Climate influenced by the Pacific Ocean and the coastal mountains.
The coastal mountains kept Beringia ice-free
On the far side of the coastal mountains lies the Pacific Ocean. Mild, wet air flows inland from the ocean up these mountains, cooling as it rises. Moisture then condenses, falling upon the peaks as snow or rain. The air becomes drier as it moves inland into the rain shadow of the coastal mountains. During colder periods of the last glacial age, not enough moisture reached Beringia to form glaciers. Far to the west, the Scandinavian ice sheet and the Tibetan Plateau blocked moist air from reaching Beringia. Today's dry inland climate is also due to the coastal mountains.
Juneau, Alaska. Photo: Ron Klein
Dry forests live in the coastal mountain rain shadow
Skunk cabbage and devil's club thrive in the wet, moderate climate of southeast Alaska, but cannot survive the short, dry summers and long, cold winters east of the coastal mountains. Instead, dry spruce and aspen forests cover much of southern Yukon. These forests are similar to the forests that occurred in this area during some of the warmer periods between past glaciations.
Dry boreal forest with lichen-covered ground, Whitehorse, Yukon. Photo:
Shawn Francis
Inset: Skunk cabbage, devil's club and Douglas fir on the Alaskan coast in Juneau.
Photo: Ron Klein
In the next century, one third to one half of all mountain glaciers may
melt and disappear, starving many rivers and lakes and changing water quality
in these areas.