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A-81 Reaches South Georgia

✇NASA Breaking News
27 October 2026 at 00:00
A large, blocky iceberg sits in dark ocean water just southwest of a long, narrow, snow-capped island. Thin clouds partly veil the scene.
Iceberg A-81 slows its drift near the edge of South Georgia’s shallow underwater shelf in this image, acquired on October 20, 2026, by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite.
NASA Earth Observatory/Michala Garrison

Some Antarctic icebergs linger close to home for decades, running aground near the ice shelves that spawned them or circling partway around the continent on coastal currents. Others, like Iceberg A-81, make a faster exit, heading north out of the Weddell Sea along a route well-traveled by the region’s bergs.

Fast is relative, though. After breaking from the Brunt Ice Shelf in January 2023, the roughly 1,550-square-kilometer (600-square-mile) berg spent more than three years in the Weddell Sea, carried along the coast by the clockwise-flowing Weddell Gyre. By May 2026, it reached the tip of the Antarctic Peninsula. It then moved north into the Scotia Sea, and by late October 2026, it approached the remote island of South Georgia in the South Atlantic Ocean, 2,300 kilometers (1,400 miles) north-northwest of the Brunt Ice Shelf.

This image, acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite, shows the berg on October 20. In the days before, its progress slowed noticeably, and it appeared to be bumping along the edge of the island’s underwater shelf, according to Jan Lieser of Australia’s Bureau of Meteorology and Christopher Shuman of the University of Maryland (retired). South Georgia has slowed and even stopped icebergs before. In 2025, for instance, Iceberg A-23A ran aground on the shelf and later broke apart.

Though Iceberg A-81 was a steadfast traveler once it broke free, it took its time in becoming an iceberg in the first place. For about 35 years, one of the Brunt Ice Shelf’s rifts known as Chasm 1 was relatively stable. Then, around 2012, it began growing again, and by 2019, it was advancing quickly enough that a break seemed imminent. But the floating glacial ice held on for several more years until finally, in January 2023, the berg let go.

Calving is a normal part of the life cycle of ice shelves, but scientists keep a close eye on Brunt, which has recently shed several large icebergs in quick succession and is home to the British Antarctic Survey’s Halley Research Station, a major base for Earth, atmospheric, and space science research since the 1950s. Besides A-81, the ice shelf calved Iceberg A-74 from the North Rift in 2021 and Iceberg A-83 from the Halloween Crack in 2024. A-74 has since broken up, while A-83 remains intact and is trailing A-81 northward, along with a handful of other icebergs that appear to be clearing out of the Weddell Sea.

NASA Earth Observatory image by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Kathryn Hansen.

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A large, blocky iceberg sits in dark ocean water just southwest of a long, narrow, snow-capped island. Thin clouds partly veil the scene.

October 20, 2026

JPEG (2.14 MB)

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Uncovering the Valleys Hidden Below Greenland’s Ice

✇NASA Breaking News
28 September 2026 at 00:00
A large map on the left shows Greenland’s bedrock topography that lies below the ice sheet. A column of smaller maps on the right zooms in on several features, including long, straight valleys on the west-central part of the island. Other insets show a megacanyon, as well as valleys radiating outward from the highlands.
A newly developed method for mapping the bedrock beneath Greenland’s ice sheet reveals the island’s hidden topography. Among the most striking finds are long, straight valleys in the west-central region, some mapped for the first time and others extending farther inland than previously known (inset 3).
NASA Earth Observatory/Lauren Dauphin, based on data from Chartrand et al.

Greenland is capped with a vast ice sheet that spans 1.7 million square kilometers (656,000 square miles) and measures more than 3 kilometers (1.9 miles) at its thickest point. Below all this ice lies a landscape human eyes have never seen directly. But a newly developed method for mapping this hidden bedrock has produced the most detailed and accurate view of it yet.

The new map reveals an expansive network of valleys carved into the surface beneath the Greenland Ice Sheet. Many of the features formed well before most of the ice above them existed, offering new context for the island’s geologic history—and potentially helping scientists refine projections of the ice sheet’s future. Scientists described the newly mapped valleys in a NASA-led paper published in Geophysical Research Letters.

The map, shown above, was derived from a method called Ice Flow Perturbation Analysis. As ice flows over a valley or ridge, the topography leaves a faint signature on the ice surface. Satellites map the ice surface in fine detail, and scientists can use these subtle bumps and dips to infer the shape of the landscape buried below. The work aims to improve future versions of BedMachine Greenland, a high-resolution dataset of the terrain beneath the ice sheet.

Using the technique, researchers manually mapped 1,943 subglacial valleys beneath the Greenland Ice Sheet, about a third of which are newly identified. About half of the valleys included in BedMachine Greenland, primarily near the ice sheet’s edge, are now known to extend farther inland than that map indicates, in some cases by hundreds of kilometers.

Some aspects of the new map align with the current understanding of how Greenland’s landscapes formed. For instance, many of the valleys appear to begin in the southern and eastern highlands, where the ice sheet is thought to have first formed. Near the eastern highlands, the map reveals a mountain range beneath the ice, with interconnected valleys and relief that increases toward the coast. These alpine-style landforms may have survived under the ice since at least the Pliocene.

Other aspects of the topography are more puzzling. The analysis indicates numerous valleys, especially in the west-central region, that are long, straight, and consistently aligned in a southwest-northeast direction. This orientation suggests a tectonic influence, generating preferential pathways along which water could flow and valleys could form. “That’s a riddle to us,” said Joe MacGregor, a NASA cryospheric scientist and co-author of the study. “Greenland is justifiably usually treated as a rigid block of old rock that is simply translated as needed to accommodate the motion and interactions of other tectonic plates.”

Separately, the angles at which the valleys branch offer another insight into their origin. Their relatively wide branching angles suggest that surface water didn’t act alone; instead, a widespread groundwater network—seeping upward and eroding the surrounding rock—likely helped carve the valleys before the ice sheet formed.

Mapping these valleys matters for understanding the ice sheet, which has continued to dramatically reshape the landscape. Ice flow concentrates in valleys, where it forms glaciers that eventually calve into fjords at the periphery of the ice sheet. This creates a reinforcing cycle: ice funneling through a valley gets thicker, thicker ice flows faster, and faster flow carves the valley even deeper.

This carving power is especially evident along western Greenland. MacGregor likened it to the glacially incised landscape at Yosemite, with Greenland’s western coast resembling, as he put it, “El Capitan after El Capitan.”

Studying the valleys also matters for the ice sheet’s future. Because the relationship between ice flow and valleys is well understood, scientists expect that as the ice sheet retreats, flow will continue to concentrate wherever the valleys already are. “The better we understand the topography now,” MacGregor said, “the better sense we’ll have of what it will look like in the longer term—beyond the next decade or two—as faster ice flow propagates into Greenland’s interior.”

NASA Earth Observatory map by Lauren Dauphin using data from Chartrand et al. Story by Kathryn Hansen.

Downloads

A large map on the left shows Greenland’s bedrock topography that lies below the ice sheet. A column of smaller maps on the right zooms in on several features, including long, straight valleys on the west-central part of the island. Other insets show a megacanyon, as well as valleys radiating outward from the highlands.

Bedrock Map

JPEG (11.10 MB)

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