Tiger Glacier flows east for 8 miles (13 km) to a tidewater terminus at the head of Icy Bay in Prince William Sound, approximately 98 miles (158 km) southwest of Valdez and 42 miles (68 km) east-southeast of Whittier, Alaska. The terminal ice face is roughly 0.5 miles (0.8 km) wide. The glacier begins at an elevation of 5,400 feet (1,646 m) in the Sargent Icefield on the Kenai Peninsula and covers an area of 15,040 acres (6,090 ha) with most snow accumulation occurring above 2,500 feet (762 m). The glacier was named in 1908 by Ulysses S. Grant and Daniel F. Higgins of the U.S. Geological Survey during a survey of the glaciers in Icy Bay. Icy Bay is a fjord extending southwest for 12 miles (19 km) from Dangerous Passage along the western coast of Prince William Sound. The bedrock exposed by the retreating glaciers around Icy Bay consists of sedimentary rocks from the Orca Group , part of the Southern Margin composite terrane. This region is a Cretaceous to Paleogene subduction-related accretionary wedge and one of the world’s largest accretionary complexes. The rock types predominantly include graywacke sandstone, siltstone, mudstone, slate, and conglomerate. These formations suggest deposition on a submarine fan in a deep ocean trench, primarily by turbidity currents.
Icy Bay was first explored on June 4, 1794, by Lieutenant Joseph Whidbey, a member of Captain George Vancouver‘s expedition. Vancouver named the bay, but it was not shown on his charts. In 1794, the glaciers in Nassau Fjord, a large bay on the northwest side of Icy Bay, likely extended into—but not across—the main part of Icy Bay. This, along with the extensive discharge of ice from these glaciers, which then formed a single ice front, probably hindered a thorough inspection of Icy Bay and the discovery of its upper reaches. Subsequent mapping errors originated from Vancouver’s depiction of Icy Bay, which was copied in later maps. However, he reported that the bay was “terminated by a compact body of ice that descended from high perpendicular cliffs to the waterside.” Tiger Glacier retreated approximately 7 miles (11 km) between 1794 and 1908, breaking up into several distinct ice streams, including Princeton, Chenega, and Tigertail glaciers. These glaciers retreated into Nassau Fjord. In 1908, Grant observed exposed rock in front of Tiger Glacier, but this rock was subsequently covered by an advancing ice flow and remained unseen until 2000.
Between 1935 and 1957, the movement of the Tiger Glacier terminus was minimal. Mature spruce trees less than a mile (1.6 km) from the terminus suggest the glacier did not expand like other regional glaciers. Since around 1960, the terminus has retreated, and by 2000, the ice was at about the same location as in 1908. The glacier terminus now consists of the Tiger Glacier flowing from the west and an unnamed glacier flowing into Icy Bay from the southwest. Tidewater glaciers end in the ocean at either a grounded terminus or a floating ice front. In 1975, Austin Post described the “tidewater glacier cycle,” where glaciers slowly advance over centuries until thinning near the terminus triggers a rapid retreat. This retreat completes within decades, stabilizing only when the glacier has retreated into shallow water. Tidewater glaciers can initiate a retreat phase due to climate changes, but once this retreat begins, its pace is largely governed by the glacier’s geometry rather than climate. These glaciers can discharge substantial amounts of ice quickly, posing a hazard to nearby shipping traffic and contributing significantly to sea-level rise. Read more here and here. Explore more of Tiger Glacier and Icy Bay here: