The McMurdo Sound sector of the West Antarctic Rift System (WARS) served as the primary local volcanic dust source during the Last Interglacial (MIS 5e) in the Allan Hills ice core records.

This is identified through geochemical fingerprints (Sr-Nd isotopes, rare earth elements, and particle characteristics) showing young volcanic material distinct from distant South American dust dominant in glacial periods.

The McMurdo Volcanic Group comprises alkaline volcanic rocks (basalts, trachytes, phonolites, and related rocks) erupted over the last ~20–25 million years (mainly Miocene to present) in the Ross Sea region. These are linked to the West Antarctic Rift System, a major extensional tectonic feature.

The West Antarctic Rift System features thinned crust, high heat flow, and widespread (often subglacial) volcanism. In the McMurdo sector, volcanism is bimodal and alkaline, with exposed rocks on the rift shoulder (Transantarctic Mountains) and islands. Aeromagnetic data suggest extensive buried volcanics beneath the Ross Sea and WAIS.

Researchers analyzed dust trapped in an Antarctic ice core from the Allan Hills Blue Ice Area. Dust composition serves as a fingerprint of its source:

During the colder Penultimate Glacial (MIS 6): Dust was mostly from distant South American sources, carried by winds over long distances.

During the warmer Last Interglacial (MIS 5e): The dust shifted to include more coarse particles with young volcanic material from the McMurdo Sound sector of the West Antarctic Rift System and nearby ice-free outcrops in the Transantarctic Mountains. This indicates much closer, local Antarctic sources.

This change implies that parts of the Ross Sea region were exposed (ice-free or with reduced ice cover), allowing local dust to be mobilized and deposited.

Earth system model simulations support this: loss of the Ross Ice Shelf and a diminished WAIS would alter winds and precipitation, strengthening transport of proximal Antarctic dust.

The WAIS is marine-based and vulnerable to ocean warming; it is currently losing mass, especially in areas like Thwaites Glacier. This paleoclimate evidence adds to concerns about potential irreversible retreat under continued warming, though exact timing, rates, and full extent during MIS 5e are still being refined. Other studies (e.g., on sediments and models) provide supporting but not identical pictures of past variability.

A new study published in Nature Geoscience (May 2026) providing evidence that the Ross Ice Shelf and parts of the West Antarctic Ice Sheet (WAIS) were significantly smaller or retreated during the Last Interglacial (MIS 5e, ~129,000–116,000 years ago).

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Ancient dust points to retreat of West Antarctic Ice Sheet during last warm period

The evidence strongly supports significant retreat or diminution of the Ross Ice Shelf and substantial parts of the West Antarctic Ice Sheet (WAIS) during the Last Interglacial (LIG/MIS 5e, ~129–116 ka), though not necessarily a complete, uniform collapse across the entire WAIS.

The 2026 Dust Provenance Study (Nature Geoscience)

This is the most direct recent evidence for the Ross sector. Researchers examined a high-resolution dust record from an ice core at the Allan Hills Blue Ice Area (East Antarctica, near the Ross Sea margin).

MIS 6 (Penultimate Glacial, colder):

Dust dominated by fine particles from distant South American sources, consistent with extensive ice cover and long-range atmospheric transport.

MIS 5e (LIG, warmer):

Pronounced shift to coarser particles with a strong young volcanic signature from local Antarctic sources — specifically the McMurdo Sound sector of the West Antarctic Rift System and exposed Transantarctic Mountain outcrops.

This requires ice-free or greatly reduced ice conditions in the Ross Sea region, exposing local bedrock and volcanic areas to wind erosion. Earth system model simulations reproduce the observed dust changes only when the Ross Ice Shelf is lost (or greatly diminished) and the WAIS is reduced, which reorganizes near-surface winds, increases precipitation along an exposed coastline, and enhances proximal dust transport.

The shift appears as early as ~134 ka (before peak LIG warmth), suggesting early sensitivity during the deglacial transition.

Lead authors (Austin Carter, Sarah Aarons, and colleagues) conclude this points to little or no Ross Ice Shelf and a diminished WAIS, contributing to elevated global sea levels.

Broader Evidence

Sea-level context:

LIG global mean sea level was ~5–10 m higher than today, with Antarctic contributions estimated up to ~5.7 m (peaking early). Greenland and thermal expansion account for part, but Antarctic (especially WAIS) loss is required to close the budget in many reconstructions.

Genomic evidence (2023):

Gene flow in circum-Antarctic octopus (Pareledone turqueti) requires complete WAIS collapse creating trans-Antarctic seaways during the LIG (or earlier interglacials like MIS 11 in broader context).

Contrasting Ronne/Filchner sector (2025 Nature study):

Sea-salt proxies from the Skytrain Ice Rise core (adjacent to Ronne Ice Shelf, Weddell Sea sector) indicate the Ronne Ice Shelf largely survived at near-modern or greater extent during most of the LIG. WAIS mass loss was significant (perhaps ~half modern mass in some estimates) but partial and heterogeneous — more pronounced in Ross/Amundsen sectors than Weddell.

This heterogeneity makes sense: the WAIS is not monolithic.

Marine-based sectors grounded below sea level (e.g., near Thwaites/Pine Island and Ross) are more vulnerable to ocean-driven melt and marine ice-sheet instability than others.

Implications

Temperatures:

LIG Antarctic temperatures were warmer than today (regional estimates vary; global ~0.5–1.5°C above pre-industrial).

Relevance to today:

The WAIS is already losing mass, particularly in the Amundsen Sea. The Ross Ice Shelf buttresses significant ice; its potential weakening is a concern. These paleo-records show the system can retreat substantially under modest sustained warming, supporting models of potential irreversibility once thresholds are crossed.

Uncertainties:

Exact timing, rates, and total volume loss are still refined. Not all proxies agree perfectly on full collapse vs. major retreat. Ongoing drilling (e.g., SWAIS2C beneath Ross Ice Shelf) will provide more sediment records.

The dust study provides compelling new proxy evidence for Ross Ice Shelf loss and WAIS diminution in that sector during the LIG, aligning with sea-level, modeling, and biological data.

Combined with the Ronne sector evidence, it paints a picture of major but regionally variable WAIS retreat — enough to contribute meaningfully to multi-meter sea-level rise, but not total disappearance everywhere. This is a critical analog for assessing future risks.

Published:  Nature Geoscience

DOI: DOI: 10.1038/s41561-026-01988-1

Provided: Columbia Climate School

Authors: Austin J. Carter, 
Sarah M. Aarons, 
Joseph C. Schnaubelt, 
Clay R. Tabor, 
John A. Higgins, 
Sarah A. Shackleton, 
Jenna A. Epifanio, 
Jacob D. Morgan, 
Janne M. Koornneef, 
Gareth R. Davies, 
Paolo Gabrielli, 
Alissa Choi, 
Jeffrey P. Severinghaus, 
Edward J. Brook, 
Douglas S. Introne, 
Julia C. Marks-Peterson, 
Johannes Sutter & 
Lindsey Davidge 

Abstract

The Last Interglacial, or Marine Isotope Stage (MIS) 5e (129–116 thousand years ago (ka)) was one of Earth’s most recent relatively warm intervals.

Global mean sea levels are estimated to have been 5–10 m higher during MIS 5e than present; however, the potential contributors to higher sea levels during this interval, such as the loss of the West Antarctic Ice Sheet, remain poorly constrained.

Here we present a high-resolution record of dust composition from an ice core at the Allan Hills Blue Ice Area, Antarctica spanning the Penultimate Glacial (MIS 6) through MIS 5e.

Geochemical data show that MIS 6 dust is dominantly sourced from South America, whereas MIS 5e dust contains young volcanic material sourced from the McMurdo Sound sector of the West Antarctic Rift System and nearby, ice-free outcrops of the Transantarctic Mountains.

Earth system model simulations show that loss of the Ross Ice Shelf and diminished West Antarctic Ice Sheet extent during MIS 5e would increase near-surface wind speeds and precipitation along an exposed Ross Sea coastline, strengthening dust transport from proximal Antarctic sources.

The agreement between the modelled circulation changes and the observed provenance shift driven by changes in wind and surface exposure suggests ice-free conditions in the Ross Sea during MIS 5e, with possible West Antarctic contributions to the elevated sea levels of this period.