Recent findings indicate major ice melt in West Antarctica started in the 1940s

Credit: Robert Larter

In the remote, icy expanses of Antarctica, the Thwaites Glacier stands as a silent witness to the changes our planet is undergoing.

Spanning about 80 miles across the western edge of the continent, this glacier is often referred to as the “Doomsday Glacier” because of its potential impact on global sea levels.

Despite its massive size, Thwaites is in trouble, losing around 50 billion tons of ice each year, a stark contrast to what it gains from snowfall. This imbalance puts the glacier’s stability in jeopardy.

Recent research led by the University of Houston has shed light on when this troubling trend began. Published in the journal PNAS, the study points to the 1940s as the start of significant glacial retreat, a timeline that aligns with similar findings from the Pine Island Glacier.

This discovery isn’t just a piece of historical trivia; it’s a crucial piece of the puzzle in understanding how climate change is reshaping our world.

Rachel Clark, a recent doctoral graduate from UH and the corresponding author of the study, emphasizes the broader implications of their findings. The retreat of Thwaites Glacier isn’t an isolated event but a symptom of the larger issue of climate change.

The initial trigger, the researchers suggest, was likely an extreme El Niño event that warmed the waters of the west Antarctic, setting off a chain reaction that the glacier has yet to recover from.

Today, Thwaites contributes to 4% of global sea-level rise, a small percentage with outsized consequences.

Julia Wellner, an associate professor of geology at UH and a lead investigator on the Thwaites Offshore Research project (THOR), points out the resilience of this change.

Even though the El Niño event was temporary, the glaciers’ retreat has been ongoing, a testament to the delicate balance of the Antarctic ice system.

The study also highlights the crucial role of the grounding zone, the point where the glacier transitions from resting on the seabed to floating on water.

The retreat in these areas suggests that external factors, such as changes in ocean and atmospheric circulation, are to blame, rather than internal glacier dynamics.

One of the key tools in this research was sediment cores collected near Thwaites Glacier. These cores, which contain layers of sediment deposited over thousands of years, were analyzed using CT scans and geochronology to construct a history of the glacier’s retreat.

Lead-210, a radioactive isotope with a short half-life, was instrumental in dating these sediments to the mid-20th century, providing a detailed timeline of the glacier’s recent past.

This method of dating is crucial because satellite observations, while invaluable, only cover the last few decades.

To truly understand how glaciers like Thwaites respond to environmental changes, scientists need data that stretches back further, which is where sediment cores come into play.

The implications of this research extend beyond academic interest. Thwaites Glacier acts as a linchpin in the stability of the West Antarctic ice sheet.

Its potential collapse could lead to a domino effect, destabilizing the entire region and contributing to a global sea-level rise of up to 65 cm (25 inches). This study, therefore, is not just about understanding the past; it’s about predicting the future.

By identifying the factors driving glacial thinning and retreat, researchers hope to refine models that predict future melting of the Antarctic ice sheet and its impact on sea levels.

The work of the THOR team, part of the larger International Thwaites Glacier Collaboration, aims to reduce the uncertainty surrounding one of the most pressing issues of our time: the rising seas that threaten communities and ecosystems around the globe.

The research findings can be found in PNAS.

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