Tyndall’s Trail of Bergs

The Southern Patagonian Icefield is the largest expanse of ice in the Southern Hemisphere outside of Antarctica. The mass of glacial ice extends hundreds of kilometers along the spine of the Andes, feeding dozens of dynamic outlet glaciers that grind their way down from higher elevations. Many of these rivers of ice terminate in the sea or in proglacial lakes.

An astronaut aboard the International Space Station photographed one of these glaciers—Tyndall Glacier in southern Chile—through a layer of ethereal clouds on May 10, 2026. Fragments of ice that had calved off its terminus were visible floating on Lago Geikie.

Like most Patagonian glaciers, Tyndall has been shrinking since the end of the Little Ice Age about 150 years ago. Lago Geikie formed at Tyndall’s terminus around 1940, according to glaciologist Mauri Pelto of Nichols College, and gradually expanded as the ice retreated. Part of the glacier previously terminated in Lago Tyndall to the east, but thinning ice cut off that outlet by 2010, Pelto said. (The ice’s retreat also exposed bedrock along its eastern edge that contains scores of ichthyosaur fossils.)

Along with thinning, ice calving off the glacier’s front has reduced its volume. Tyndall has lost 2.2 kilometers (1.4 miles) in length since November 2022, Pelto said, following about a decade of limited retreat with considerable thinning. A significant calving event in March and April 2023 contributed to the recent uptick in ice retreat. During that time, satellites observed several large icebergs breaking away from Tyndall’s terminus.

Austral autumn in 2026 was a time of active calving retreat at Tyndall (and some neighboring glaciers), Pelto said, albeit more incremental than three years prior. “The substantial crevasses crisscrossing the glacier near the calving front lead to many smaller icebergs,” he said. On the other hand, larger tabular icebergs tend to form when there are fewer deep crevasses near the terminus and the glacier’s ice is thinner.

The ice cliff at the terminus casts a substantial shadow, which can help scientists estimate the height of the glacier’s front. Pelto’s calculations, using information about the Sun’s position provided with the image, indicate that Tyndall’s front loomed 30–40 meters (100–130 feet) above the lake surface in May 2026. Observations from orbit, including astronaut photographs, can help scientists monitor and understand glaciers in remote regions where ground-based observations are scarce.

As for what comes next for Tyndall, Pelto expects many more small icebergs to continue breaking off, given the heavily crevassed appearance of the calving front. “Look for a burst of iceberg production next fall.”

Astronaut photograph ISS074-E-582898 was acquired on May 10, 2026, with a Nikon Z9 digital camera using a focal length of 560 millimeters. It is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at NASA Johnson Space Center. The image was taken by a member of the Expedition 74 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Story by Lindsey Doermann.