Earthshots: Satellite Images of Environmental Change

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» Hubbard Glacier, Alaska, USA

Unlike many glaciers in Alaska and around the world, Hubbard Glacier is thickening and advancing. Hubbard Glacier has a large accumulation area, like a river with a large watershed. This large area of snow in the mountains upstream either melts or flows down to the end of the glacier, and Hubbard steadily grows. In fact, Hubbard Glacier has advanced 1.5 miles, or about 2.4 kilometers, since 1895.

These Landsat images illustrate an unusual event that was observed twice at the terminus of Hubbard Glacier. Hubbard temporarily blocked Russell Fjord (a long, narrow inlet of the sea) from the rest of Disenchantment Bay and the Gulf of Alaska. It’s even possible that the glacier could one day permanently block the fjord.


Map of the featured area.

Hubbard Glacier slides in from the north in these images. Two bodies of water meet at the end of the glacier. Disenchantment Bay extends to the southwest into Yakutat Bay, which eventually connects to the Gulf of Alaska. Russell Fjord is the narrow body of saltwater extending southeast and is connected to Disenchantment Bay.

In May 1986, Hubbard Glacier blocked the outlet of Russell Fjord, creating a dam that formed “Russell Lake.” That summer, the new lake filled with runoff; its water level rose 25 meters, and a decrease in salinity levels threatened its marine life.

Around midnight on October 8, 1986, the dam began to give way. In the next 24 hours an estimated 5.3 billion cubic meters of water gushed through the gap, and the fjord was reconnected to Disenchantment Bay, returning to its previous level.

Hubbard Glacier blocked the entrance to Russell Fjord again in 2002. The blockage started in June and raised the level of the lake to 18.5 meters above sea level. On August 14, the ice dam broke free, and for the next day and a half, the channel was full of fast-moving ice chunks and debris. By the morning of August 15, the lake level had dropped to 4.8 meters above sea level.

If the glacier permanently blocks Russell Fjord, the fjord would turn into a 64-kilometer-long lake. This lake would eventually drain into the Situk River at the lake’s southern end. This would disrupt the river’s fisheries and potentially threaten the tourism and economy of Yakutat.

A 2015 study found that, given the rate of the glacier’s advance over the past few decades, it’s unlikely that the channel will remain open by the end of this century. Since Hubbard Glacier has been continuously advancing since 1895, there’s good reason for concern over this possibility.

The 2010 and 2015 images show an open channel from Russell Fjord to Disenchantment Bay. But notice that even when the channel is open, the opening is narrow. In the 2015 Landsat image, the channel is about 540 meters wide. The channel width also varies annually.

If you would like a more scientific explanation of the phenomenon, read a short journal article written by two USGS scientists. And see the USGS press release describing the 2002 event.


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