AK - The Mighty Taku Glacier Takes a Bow
After advancing for over a century, a massive glacier near Juneau, Alaska, is poised for accelerated retreat and the birth of a new fjord.
In a world of shrinking glaciers, that yet another is melting hardly seems newsworthy. But the imminent retreat of the massive Taku Glacier near Juneau, Alaska, which until recently was still growing, is an exception. And while it does mark another unhappy milestone in the ongoing climate crisis, it also prompts thinking about how the glacier’s retreat will soon reshape the ecology of the Taku River valley. Paradoxical to its grim associations, the shrinking of the Taku Glacier will create new habitat for local wildlife, and bring fresh opportunities for recreation and science.
The Taku Glacier, called T’aaḵú Ḵwáan Sít’i in the Tlingit language, lies within the traditional homeland of the Taku River Tlingit First Nation. Winding 55 kilometers from the Juneau Icefield, the glacier forms a sprawling lobe beside the mouth of the Taku River, a biologically abundant waterway that cleaves its way to the Alaska coast from the mountains of British Columbia. Although the glacier has retreated in past centuries, it has been steadily advancing since the late 19th century.
This makes the Taku an outlier among North America’s coastal glaciers. As most of its counterparts shed ice throughout the 20th century, the Taku steadily added girth. Like an ice-age holdout, it buried a deep-water fjord and swelled up against steep mountainsides, obliterating ancient coastal rainforest. At its leading edge, it shoved sediment into a moraine nine kilometers across. The debris buried the glacier’s nose, and on its surface new plants and trees sprouted—even as the ice continued to push them toward the edge of the Taku River.
But that heyday appears to be over. Chris McNeil, a geophysicist with the US Geological Survey who first studied the Taku Glacier in 2009, reports that a freshwater moat has now formed along the glacier’s face, indicating that it is melting back from its moraine. McNeil attributes this initial retreat to climate change, which he says has raised local temperatures by 2 °C in recent decades.
However, other forces will soon be at work. As the Taku continues separating from its moraine, the moat will gradually expand into a lake 100 or more meters deep, McNeil says, which will be dammed from nearby ocean waters by the moraine. The lake water will exert a new erosional force on the ice that was once safely insulated by the moraine. Independent of the warming climate, it will speed the glacier’s decay. As time goes on, the shape and depth of the glacier’s basin may force additional erosion—a process tied more to physics than to climate.