North Dawes Glacier originates in the Stikine Icefield at roughly 5,200 feet (1,585 m) on the western flank of Sheppard Peak and flows southwest for 15 miles (24 km) to a proglacial lake at 1,000 feet (305 m) above Endicott Arm, about 74 miles (119 km) southeast of Juneau and 51 miles (82 km) north of Petersburg, Alaska. The lake, about two miles (3.2 km) long, drains via a stream 1.3 miles (2.1 km) long into an inlet extending north from Endicott Arm. The glacier takes its name from Dawes Glacier at the head of Endicott Arm, which was named in 1891 by the US Geological Survey for Henry L. Dawes, a Massachusetts senator who sponsored the Dawes Act. North Dawes was first reported in 1961 by the US Geological Survey. At higher elevations, bedrock comprises the Coast Plutonic Complex—mainly granodiorite exposed on peaks that protrude through the icefield. Beneath most of the flowing ice are metamorphosed schists and gneisses derived from sedimentary and volcanic rocks older than 66 million years. Near sea level along Endicott Arm, the bedrock is tonalite with some quartz diorite, formed during the waning stages of deformation and metamorphism in the Coast Mountains between the Late Cretaceous and Paleocene (about 100 million to 56 million years ago).
When John Muir visited Endicott Arm in the 1880s, North Dawes Glacier was calving ice directly into the fjord. By 1923 the terminus had retreated from tidewater. Between 1941 and 1961, William O. Field of the American Geographical Society documented a further retreat of 1.1 miles (1.8 km). By 1990, satellite imagery showed the terminus in a proglacial lake about 0.8 miles (1.2 km) long; by 2005 the glacier had retreated another 0.8 miles (1.3 km) and the lake had grown to 1.6 miles (2.5 km). By 2013 the glacier had withdrawn entirely from the lake—a combined retreat of 1.9 miles (3.1 km) since 1990. The retreat reflects a diminished accumulation of ice and an increased melt rate, causing thinning and exposure of new bedrock. The accumulation zone, mainly between 3,120 and 3,610 feet (950–1,100 m), now lies below the summer snowline. North Dawes is retreating at roughly the same rate as the nearby South Sawyer Glacier—which originates from the same icefield—but is losing a greater percentage of its total area and length.
Most glaciers in Southeast Alaska are thinning, many of them rapidly. The largest ice losses are occurring at tidewater glaciers, where thinning of up to 2,100 feet (640 m) has been recorded in terminal reaches and 330 feet (100 m) or more at higher elevations. The tidewater glacier cycle, first described by Austin Post in 1975, refers to the typically centuries-long pattern of advance, rapid retreat, and intervening stability. Instability begins when a terminus retreats from a protective shoal or submerged moraine into deeper water, triggering rapid calving. Positive feedbacks then accelerate the process: surface slopes and flow velocities increase, causing significant drawdown of the parent icefield and further calving at the terminus. This phase can produce terminus retreat exceeding 0.6 miles (1 km) per year in southeast Alaska. Because the volume of ice lost at tidewater glaciers so far exceeds that of non-calving glaciers, retreating tidewater glaciers tend to be the dominant contributors to sea-level rise in the region. Read more here and here. Explore more of North Dawes River and Endicott Arm here: