Massive Ice Shelf Once Locked Northern Ice Sheets in Place—Its Collapse Holds Clues for Antarctica’s Future

A massive floating ice shelf in Baffin Bay (west of Greenland) once buttressed three major Northern Hemisphere ice sheets during the Last Glacial Maximum (~20,000 years ago). Its later disappearance helped accelerate glacier retreat and contributed to substantial sea- level rise. The finding offers a paleo-analog for how loss of buttressing ice shelves could affect Antarctica today.

About 20,000 years ago, an enormous ice shelf more than a mile (~1.4- 2.1 km) thick occupied Baffin Bay. It helped restrain the margins of the Greenland Ice Sheet (to the east), the Innuitian Ice Sheet (to the north), and the Laurentide Ice Sheet (to the west).

Researchers describe these ice sheets as resembling a gothic cathedral, with the floating ice shelves acting as flying buttresses that slow the flow of grounded ice into the ocean.

Key findings

• Scientists from the University of Florida (including co-author Robert Hatfield), University of North Carolina Wilmington, Columbia University, and other institutions mapped the seafloor using multibeam bathymetry and collected sediment cores during a research cruise on the R/V Neil Armstrong. They identified a sharp “Ice Contact Boundary” marking where the ice shelf was grounded versus floating. These features occur at depths up to ~1,800 m, deeper than any previously documented glacial bedforms in the Northern Hemisphere, indicating an unusually thick ice shelf.⁠
• The shelf was comparable in area to major modern Antarctic ice shelves (larger than most except the Ross and Ronne) and thicker at its grounding zone than typical modern Antarctic shelves.
• Sediment evidence shows the ice shelf disappeared over roughly 500- 1,000 years. Once the buttressing was lost, the land- based glaciers flowed faster into the sea, melted, and contributed to hundreds of feet of sea- level rise that helped shape modern coastlines.

The results were published on October 21, 2026, in Nature Geoscience. The discovery was unexpected; the team originally aimed to study what destabilized the western Greenland Ice Sheet at the end of the last ice age.

Relevance to Antarctica today

Ice shelves play a critical stabilizing role. When they thin, break up, or disappear, the grounded ice behind them can accelerate, increasing ice discharge and sea- level contribution, exactly the concern for parts of Antarctica (e.g., around Thwaites or Pine Island glaciers).

This ancient Baffin Bay example shows that a large, thick ice shelf on the scale of major Antarctic ones can vanish in centuries, providing a real- world case study of the mechanisms and timescales involved. It supplies new constraints for ice- sheet models, potentially improving projections of how quickly Antarctic ice could respond if buttressing is lost.⁠

In short, the past behavior of this Northern Hemisphere ice shelf underscores the importance of monitoring and understanding Antarctic ice shelves as climate warms, because their loss can unlock much larger volumes of ice on land.

The Baffin Bay Ice Shelf stabilized three adjacent ice sheets during the last glacial period

The Baffin Bay study is valuable as a paleo- analogue, it shows how the loss of a large, thick ice shelf can destabilize marine- based ice sheets, but it does not imply any direct connection between the northern and southern ice sheets.

Abstract summary

During the Last Glacial Maximum (roughly 26,500- 19,000 years ago), the Laurentide, Innuitian, and Greenland ice sheets coalesced around Baffin Bay, a semi- enclosed basin between Greenland and Canada. The exact configuration of their marine- terminating margins had been unclear.

Using compiled bathymetric data and a geomorphic study of the Baffin Bay continental slope, the authors identify evidence of slope- grounded ice and trace its maximum- depth imprint around most of the bay. They interpret these ice- contact features as the signature of a basin- spanning ice shelf that was ~1,400– 2,100 m thick (after correction for relative sea level). The shelf covered approximately 150,000 km².

This extensive ice shelf, supported by the basin’s geometry, buttressed, mechanically coupled, and promoted thickening of the three adjacent ice sheets. Sediment- core evidence indicates that collapse of the ice shelf triggered rapid ice- sheet retreat, linking abrupt Northern Hemisphere ice-sheet instability to embayment- scale ice- shelf dynamics.

The Baffin Bay Ice Shelf serves as a paleo-analogue showing that ice-shelf loss can rapidly reorganize marine ice sheets, relevant to how weakening buttresses may accelerate future Antarctic ice, stream retreat.

Key supporting details from related coverage

• Authors include Shannon A. Klotsko (University of North Carolina Wilmington), Robert G. Hatfield (University of Florida), Brendan T. Reilly (Columbia University / Lamont- Doherty), and others.⁠
• Ice- contact boundary (ICB) features were mapped at water depths up to ~1,800 m, deeper than previously recognized Northern Hemisphere glacial bedforms.⁠
• The shelf was thicker at its grounding zone than most modern Antarctic ice shelves (which reach similar thicknesses only near major feeder glaciers) and comparable in area to large present- day Antarctic shelves (except the Ross and Ronne).
• Data (shapefiles of geomorphic mapping, processed bathymetry grids) are publicly available via the Marine Geoscience Data System.

This is the peer- reviewed paper underlying the University of Florida news release discussed previously. The full text beyond the abstract is behind a paywall and institutional access.

Journal: Nature Geoscience

DOI: 10.1038/s41561-026-02126-7

Provided: University of Florida

Authors: Shannon A. Klotsko,
Robert G. Hatfield,
Brendan T. Reilly,
Anne E. Jennings,
Andrew M. W. Newton,
Erin E. Gregory,
Alan C. Mix,
Joseph S. Stoner,
Maureen H. Walczak,
Jacqueline Austermann &
Lauren Lewright