South Sawyer Glacier originates in British Columbia and flows 31 miles (50 km) northwest to the head of Tracy Arm, a fjord roughly 73 miles (118 km) north of Petersburg and 56 miles (90 km) southeast of Juneau, Alaska. Lieutenant Commander Henry B. Mansfield of the U.S. Navy named both the glacier and the fjord in 1889, the latter after Benjamin F. Tracy, a Union brigadier general in the Civil War who later served as secretary of the navy under President Benjamin Harrison. From the glacier’s terminus, Tracy Arm runs northwest for 18 miles (29 km), then southwest for 10 miles (16 km) to Holkham Bay. Flanked by steep mountains, the fjord is fed by the Sawyer and South Sawyer glaciers and their tributaries.
In the 1980s, water depth at South Sawyer Glacier’s terminus measured 590–650 feet (180–200 m), and its calving front retreated at roughly 1 mile (1.8 km) a year. The glacier retreated 2 miles (3.5 km) between 1899 and 1967, then changed little until 1985. From 1985 to 2016 it retreated a further 1.4 miles (2.3 km), most of that loss occurring between 1996 and 2016. Rising regional snowlines drove this retreat, as they have for the nearby North Dawes, Baird, Dawes and Sawyer glaciers. By 2016 the calving front’s velocity had slowed to under 2,900 feet (900 m) a year, and the terminus water depth had shallowed to 360 feet (110 m). Just south of the terminus, a smaller tributary glacier that had been a single ice mass in 1985 split into two arms, which retreated 2.8 miles (4.5 km) in the west and 2.4 miles (3.8 km) in the east. South Sawyer Glacier now sits close to the tidewater limit of Tracy Arm.
On August 10th 2025, a landslide above the glacier’s toe, with its base exposed by weeks of rapid retreat, sent more than 35.3 million cubic feet (64 million cubic meters) of rock into the fjord, triggering a tsunami that stripped vegetation up to 1,580 feet (481 m) above sea level on the opposite wall. It was the second-highest tsunami ever recorded, surpassed only by the 1958 Lituya Bay tsunami in Alaska, which killed five people; near Sawyer Island, where the South and North Sawyer fjords meet, the wave still reached over 100 feet (30 m). The Alaska Earthquake Center detected the slide from seismic signals within minutes, and kayakers camped nearby reported their gear swept away, though no injuries were reported. Researchers later identified three smaller precursory slope failures since 2017 and days of faint seismic activity before the collapse, offering potential warning signs for predicting similar landslide-tsunamis at other retreating glaciers. Read more here and here. Explore more of South Sawyer Glacier and Tracy Arm here: