Is Antarctica Losing Its Grip? 30 Years of Ice Retreat

Gerd Dani 0

Satellite radar imagery showing 30 years of grounding line retreat on Pine Island and Thwaites glaciers, Antarctica, with colored lines from black (1992) to red (2025).

What happens when the ice beneath an entire continent starts to lose contact with the Earth itself?

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On March 2, 2026, a team of researchers led by Eric Rignot at the University of California, Irvine, published a landmark study in Proceedings of the National Academy of Sciences (PNAS). They tracked 30 years of glacier grounding line changes across all of Antarctica — from 1992 to 2025 — using data from 15 different satellites. Their findings? About 12,820 km² of ice that once sat firmly on bedrock has shifted to a floating state. That's roughly the size of the Campania region in Italy, or about twice the area of metropolitan Los Angeles.

But don't stop here. This article goes deeper — glacier by glacier, region by region — so you can truly understand what's happening at the bottom of our world. Stick with us to the end. You won't regret it.

What Exactly Is a Grounding Line — and Why Should We Care?

Picture a glacier as an enormous river of ice flowing from the interior of a continent toward the ocean. At some point along its path, the ice lifts off the bedrock and begins to float on seawater. The exact boundary where that transition happens is called the grounding line.

Think of it like this: imagine holding a piece of wood flat against a table, then slowly pushing it over the edge. The point where the wood stops touching the table and starts hanging in the air? That's your grounding line.

This boundary controls the glacier's stability. Ice that rests on rock stays put. Ice that floats is exposed to ocean currents and warm water from below — making it far more vulnerable to melting and breakup. When a grounding line retreats inland, it means more ice has become unanchored. And unanchored ice contributes directly to rising seas.

The Antarctic Ice Sheet, by the way, holds enough frozen water to raise global sea levels by 57 meters if it all melted. No one expects that to happen anytime soon, but even a small percentage matters enormously.

Why Is It So Hard to Measure?

You can't simply walk up to a grounding line and mark it with a flag. It sits beneath hundreds of meters of ice, at the point where glacier meets ocean — hidden from view. The line also shifts with the tides, sometimes moving several kilometers back and forth in a single day.

Scientists have learned, though, that this boundary is better described as an "ice grounding zone" (IGZ) rather than a single line. The zone can stretch across several ice thicknesses — multiple kilometers wide — because of complex interactions between tides, pressurized seawater, the shape of the bedrock, and subglacial freshwater flowing beneath the ice.

How Do Scientists Track an Invisible Boundary From Space?

Here's where the technology gets truly impressive.

Researchers use a technique called differential synthetic aperture radar interferometry (DInSAR for short). Satellites like Europe's Copernicus Sentinel-1 send radar signals down to the ice surface and measure tiny changes in how that surface moves over time.

The principle is elegant: floating ice rises and falls with the tides; grounded ice doesn't. By comparing radar images taken days apart, scientists can detect movements as small as a few millimeters. That's enough to pinpoint where the ice transitions from grounded to floating — and to track how that boundary shifts over years and decades.

Rignot's team didn't rely on just one satellite. They stitched together data from 15 missions spanning three decades:

  • ERS-1 and ERS-2 (European Space Agency, launched 1991 and 1995)
  • Sentinel-1a and 1b (ESA, 2014 and 2016) plus the new Sentinel-1c (December 2024)
  • RADARSAT-1, RADARSAT-2, and the RADARSAT Constellation Mission (Canadian Space Agency)
  • ALOS PALSAR and PALSAR-2 (Japanese Space Agency)
  • CosmoSkyMed (Italian Space Agency)
  • ICEYE (commercial constellation, operating since 2020)

Each satellite operates at slightly different radar frequencies — C-band, L-band, or X-band — and different repeat intervals. Combining all of them gives scientists their most complete and continuous picture of Antarctica's grounding zones ever assembled.

For the 2018–2020 period, the team also used a machine learning algorithm to map grounding lines automatically, followed by human verification. The precision of the automated system matched that of expert analysts.

What Did 30 Years of Satellite Data Reveal?

Let's start with the reassuring part.

Over 77% of Antarctica's coastline showed no grounding line movement. Across roughly 31,390 km of ice shelf and glacier grounding lines, the vast majority stayed within ±1 km of their original position — well within the margin of measurement uncertainty.

Now the less comforting part.

Along the remaining 23% — about 7,205 km of coastline — the grounding line has retreated. Some areas have pulled back by just a few kilometers. Others have retreated by more than 40 km in three decades.

Between 1996 and 2025, the ice sheet lost a total of 12,820 ± 1,873 km² of grounded ice. That works out to an average of 442 ± 64 km² every single year.

Where did it all go?

Table 1 — Grounded Ice Loss by Antarctic Region (1996–2025)
Region Area Lost (km²) Share of Total
West Antarctica 7,947 ± 1,016 ~62%
East Antarctica 3,519 ± 633 ~28%
Antarctic Peninsula 1,354 ± 225 ~10%
Total Antarctica 12,820 ± 1,873 100%

West Antarctica dominates the losses — accounting for nearly two-thirds of all grounded ice retreat on the continent.

West Antarctica: Where Retreat Runs Fastest

If Antarctica has a weak spot, it's right here. The glaciers draining into the Amundsen Sea and along the Getz Ice Shelf show some of the most dramatic grounding line retreat anywhere on Earth.

The Amundsen Sea Sector

This area includes some names you may have heard in the news: Pine Island, Thwaites, Pope, Smith, and Kohler glaciers.

Smith Glacier holds the record in this study: its grounding line pulled back a staggering 43 km between 1992 and 2025. Pine Island retreated 33 km. Thwaites — often called the "Doomsday Glacier" in popular media — retreated 26 km along its deep, fast-flowing core. Pope Glacier lost 23 km, and Haynes Glacier, which barely had a floating section in 1996, retreated 25 km to form an entirely new ice shelf covering 536 km².

The Haynes Glacier has been retreating at roughly 1 km per year since 2019. That's a speed that's hard to process when we're talking about a structure made of solid ice.

Table 2 — Major Glacier Retreat in West Antarctica (1996–2025)
Glacier Retreat (km) Area Lost (km²)
East Getz Ice Shelf 9 1,733 ± 352
Thwaites 26 1,161 ± 62
Smith 43 1,051 ± 25
Pine Island 33 1,035 ± 108
Haynes 19 536 ± 35
Pope 23 309 ± 20
Kohler 9 328 ± 87

Here's something striking about the Thwaites Eastern Ice Shelf: it's held in place by an ice rise — a mound of grounded ice within the shelf that acts like a speed bump. In 1996, that ice rise covered 74 ± 5 km². By 2024, it had shrunk to just 14 ± 2 km² — a fivefold reduction. When that anchor disappears, the shelf could destabilize much faster.

The Getz Ice Shelf and Surrounding Glaciers

The East Getz sector actually recorded the single largest area of grounded ice loss in all of Antarctica: 1,733 ± 352 km². Berry Glacier retreated 19 km, Hull Glacier pulled back 14 km along an overdeepened bedrock channel, and Venzke Glacier lost 8 km. The retreat spans the entire Getz Ice Shelf, concentrated along the fast-flowing glacier outlets.

The retreat rates in West Antarctica are among the fastest on the planet. For comparison, Alaska's Columbia Glacier — one of the fastest retreating glaciers in the Northern Hemisphere — retreated at 0.6 km per year between 1980 and 2011. Greenland's Jakobshavn Glacier pulled back at a similar pace from 1996 to 2016. West Antarctic glaciers are retreating two to three times faster than either of these, particularly where the bedrock slopes downward toward the interior of the continent.

East Antarctica: Not as Safe as We Thought?

East Antarctica is the larger, colder, and generally more stable half of the continent. For a long time, many assumed it was mostly immune to rapid change. This study suggests otherwise — at least in some areas.

Wilkes and George V Lands

Several major glaciers in Wilkes Land and George V Land show clear retreat:

  • Vanderford Glacier retreated a remarkable 26 km along an overdeepened bed, losing 513 ± 50 km² of grounded ice. In recent years, the retreat has slowed as the bedrock rises to a higher elevation at its current grounding line position.
  • Totten Glacier — one of the most closely watched glaciers in East Antarctica — has retreated 10 km since 1996, losing 581 ± 87 km² of grounded ice.
  • Moscow University Ice Shelf lost 660 ± 102 km², with the two branches of its main glacier retreating 2 to 6 km.
  • Cook Ice Shelf pulled back 10 km along its western, fast-flowing core. This glacier lost its buttressing ice shelf back in the 1970s.
  • Mertz Glacier retreated 10 km along its deeper western flank.
  • Denman Glacier retreated 12 km, and scientists detected 13-km-long seawater intrusions extending beneath the grounded ice in 2021, 2023, and especially 2025 — reaching into one of the deepest bedrock trenches in all of East Antarctica.

That last detail about Denman is worth pausing on. Seawater pushing 13 kilometers inland beneath a glacier means warm ocean water is penetrating far deeper into the ice sheet than the surface tells us. It's a red flag.

What Stayed Stable

The enormous Amery Ice Shelf — which has a grounding line sitting at a record depth of 2.5 km — showed no retreat from 1996 to 2024. That's good news. The Ross Ice Shelf, the largest ice shelf on Earth, also appears stable based on comparisons between 2009 radar data and 2019–2020 ICESat-2 laser altimetry.

The Antarctic Peninsula: Collapse and Recovery

The Antarctic Peninsula — that long finger of land reaching northward toward South America — tells a more complicated story.

On the eastern coast, dramatic retreats followed the collapse of the Larsen A and Larsen B ice shelves. Edgeworth Glacier retreated 16 km and now supports only a 5-km-long ice shelf. Hektoria Glacier pulled back 21 km, Green 16 km, and Evans 9 km. The combined loss for the eastern side of the Peninsula totals 413 ± 20 km² — all from the Larsen B area and further north.

Something interesting is happening, though. Several of these glaciers have reformed new floating ice shelves during their retreat. Hektoria now develops a 2.3-km-long ice shelf. Even Fox and Ferrigno ice streams in West Antarctica have more extensive floating sections today than they did decades ago. A retreating glacier doesn't always mean a shrinking ice shelf — and a reformed shelf can actually slow down further retreat by resisting the outflow of ice from the continent. Scientists call this a negative feedback mechanism.

On the western coast, the Wordie Ice Shelf has been retreating for decades. New data from the ICEYE satellite constellation in 2025 revealed a 10-km-long ice shelf at the mouths of Airy, Seller, and Flemming glaciers. The George VI Ice Shelf also shows retreat of 3 to 7 km along several tributary glaciers.

One important observation: the eastern Antarctic Peninsula is the only area of retreat in Antarctica that isn't driven by warm Circumpolar Deep Water. Here, the ocean is much colder. The retreat is instead linked to ice shelf collapses — triggered by warmer air, reduced sea ice cover, and the sudden loss of thick ice mixtures that once glued everything together.

What's Driving the Retreat? The Role of Warm Ocean Water

Across most of Antarctica, one physical process explains the pattern of retreat better than any other: warm Circumpolar Deep Water (CDW) reaching the base of glaciers.

CDW is a relatively warm ocean current — we're talking about water just a degree or two above freezing, but that's enough to cause serious melting when it comes into direct contact with ice. A shift in wind patterns (specifically, a poleward movement of the westerly winds) has pushed more of this warm water onto the Antarctic continental shelf in recent decades.

When CDW reaches the grounding zone, it melts ice from below. That reduces the friction holding the glacier to the bedrock, which allows the ice to speed up and thin. If the bedrock beneath slopes downward toward the interior — what scientists call a retrograde bed — the retreat accelerates, because deeper ice exposes more surface area to warm water. This self-reinforcing cycle is described by the marine ice sheet instability theory.

The numbers tell a clear story:

  • Antarctic glaciers retreat at 0.3 to 0.6 km per year on prograde slopes (where the bed rises inland).
  • On retrograde slopes, the rate jumps to 1 to 3.6 km per year — roughly six times faster.

Data from sea mammals in East Antarctica suggest that mid-depth CDW warmed by 0.8 to 2.0°C along the continental slope between the 1930–1990 period and 2010–2018, driven by the summer shift of the westerly winds toward the pole.

The presence of warm CDW is well documented in front of Pine Island, Thwaites, Pope/Smith/Kohler, and the Getz Ice Shelf in West Antarctica. In East Antarctica, warm water has been detected near Vanderford, Totten, and Denman glaciers. For many other retreating glaciers, the oceanographic data are still sparse — which is precisely why more research expeditions are urgently needed.

Where the Seafloor Blocks Warm Water

Bathymetry — the shape of the ocean floor — plays a huge role. Where shallow sills or ridges exist on the continental shelf, they can block warm CDW from reaching glacier grounding zones. This explains why the Fimbul, Riiser-Larsen, and Queen Maud Land ice shelves remain stable: shallow underwater barriers keep the warm water out.

The same logic applies to the Abbot and Cosgrove ice shelves in West Antarctica. And the Nickerson Ice Shelf may owe its stability to a shallow seafloor, though the data are incomplete.

Where Is Antarctica Holding Steady?

We've spent a lot of time on what's retreating. Let's take a breath and look at what's stable — because it's the majority of the continent.

The Ross Ice Shelf and the Filchner-Ronne Ice Shelf — the two largest ice shelves on Earth — show no grounding line movement. These are separated from warm CDW by broad stretches of cold ocean water.

The entire coastline of Queen Maud Land is stable, including the Vigrid, Nivi, Lazarev, Borchgrevink, and Roi Baudoin ice shelves. The Jutulstraumen Ice Stream, a major glacier flowing into the Fimbul Ice Shelf, shows the exact same grounding position in 2023 as it did in 1994.

The Amery Ice Shelf, despite sitting above one of the deepest grounding lines ever measured (2.5 km below sea level), has not retreated. The Shirase Glacier in Enderby Land is also stable — somewhat surprisingly, since there is warm CDW at its front. Scientists suspect shallow ocean floor features in front of the glacier limit the heat getting in.

Ice shelves with many pinning points — spots where the ice shelf touches the seafloor — tend to be stable. These pins act like anchors, providing resistance to flow and implying shallow water beneath. This pattern applies to ice shelves across Queen Maud Land, the Shackleton, Voyeykov, West, and Dibble ice shelves, among others.

What Does This Mean for Global Sea Level?

When a grounding line retreats, the ice that transitions from grounded to floating doesn't immediately raise sea levels — but it sets the stage for future contributions. Floating ice that was already displacing ocean water doesn't add volume when it melts. The concern is what comes next: as the grounding line moves inland, it exposes more land-based ice to the forces that push it toward the sea.

The study found something worth serious attention regarding the ice grounding zone itself. The grounding zone — that band between fully grounded and fully floating — spans several kilometers wide, not just a single line. Current ice sheet models often treat it as a narrow boundary. But if melt occurs across this entire wide zone (because pressurized seawater is penetrating beneath grounded ice at high speeds), then projections of sea level rise from Antarctica could increase by up to a factor of two, according to previous modeling work.

That's not a typo. Accounting for a realistic grounding zone in computer models could double the predicted sea level contribution from Antarctic ice.

Key formula — Horizontal displacement due to ice bending:

u(x) = −H·β·A(t)·e−βx·sin(βx)

Where H is ice thickness, β is the flexural wavenumber, A(t) is tidal amplitude, and x is the distance from the grounding line. This equation describes how ice bends and shifts horizontally near the grounding zone — and it shows that the apparent position of the grounding line in radar data is systematically shifted inland by roughly one-third of the ice thickness for typical radar incidence angles (~35°).

Looking Ahead: Which Glaciers Face the Greatest Risk?

Based on the study's findings, future retreat is most likely to continue — and possibly accelerate — along glaciers sitting on overdeepened beds (where the bedrock slopes deeper inland) that are exposed to warm Circumpolar Deep Water.

In West Antarctica, the candidates include Ferrigno Ice Stream, Pine Island, Piglet, Smith West, and Berry glaciers. If warm water eventually reaches farther south, the Bailey, Slessor, and Recovery ice streams would be highly vulnerable because they drain a vast marine-based sector along retrograde slopes.

In East Antarctica, Denman, the Cook Ice Shelf, and Ninnis Glacier stand out as areas of concern. The 13-km seawater intrusions beneath Denman, extending into one of the continent's deepest bedrock trenches, are an early warning sign.

One finding that challenges older models: glaciers don't always stop retreating when they reach prograde slopes (where the bed rises inland). Thwaites, Kohler, Pope, Haynes, Hull, Moscow University, and Totten are all continuing to retreat along prograde terrain. The presence of a rising bed doesn't guarantee stability — a reminder that the physics of ice sheet retreat is more complex than simple theory predicts.

Final Thoughts

Thirty years of satellite data have given us the clearest picture yet of what's happening at the edges of the Antarctic Ice Sheet. Most of the continent's ice — over three-quarters of it — remains firmly anchored to the ground. That's worth remembering on days when the news feels overwhelming.

But in specific, well-identified areas, the changes are rapid and sustained. Warm ocean water is reaching places it didn't reach before. Bedrock geometry is amplifying retreat. Ice rises that once stabilized entire shelf systems are shrinking. And the rate of grounding line retreat in West Antarctica is two to three times faster than anything we see in Alaska or Greenland.

What we do with this knowledge is up to us. The science is here — drawn from 15 satellite missions, 30 years of observations, and the work of researchers across multiple countries and space agencies. Their data are publicly available, deposited at both the Dryad Digital Repository and NASA's National Snow and Ice Data Center.

At FreeAstroScience, we believe that understanding is the first step. We break down complex science because we think everyone deserves to see the world clearly — not through fear, but through knowledge. As we like to say: the sleep of reason breeds monsters. Keep your mind awake. Keep asking questions.

Come back to FreeAstroScience.com whenever you want to learn something new. We'll be here, making the complicated simple — one article at a time.

Sources

  1. Rignot, E., Scheuchl, B., Barre, J.B., et al. (2026). "Thirty years of glacier grounding line retreat in Antarctica." Proceedings of the National Academy of Sciences, Vol. 123, No. 10, e2524380123. Published March 2, 2026. DOI: 10.1073/pnas.2524380123

  2. Bernardi, L. (2026). "L'Antartide in 30 anni ha perso 12.800 km² di ghiaccio sul suolo." Geopop, March 5, 2026. Link

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