Over the past decade, the melting of ice has accelerated further

In the High Arctic, encountering an orca used to be a rare event. Even for the powerful killer whale, this icy region of the planet represented too great a danger, one of the few places it dared not venture. But with the retreat of the sea ice, the Arctic now offers new hunting grounds suitable for orcas.

"With the rapid retreat of sea ice in the Arctic, orcas are gaining new access routes to regions such as Hudson Bay and the High Arctic," explains Steve Ferguson on Yale Environment 360. According to this scientist from Fisheries and Oceans Canada, "alongside the polar bear, they have become the main predators of the region."

"In a spirit of collaboration, we analyzed the strengths and weaknesses of each method and made the necessary adjustments to make the data comparable," explains Enrico Mattea, a researcher in the Department of Geosciences at the University of Fribourg.

The melting of the ice not only affects sea level, it also disrupts marine ecosystems. Hence the need to closely monitor its evolution. Until now, the data were disparate and difficult to compare. To remedy this, scientists created an international alliance, grouped around the GlaMBIE (Glacier Mass Balance Intercomparison Exercise) project.

"In a spirit of collaboration, we analyzed the strengths and weaknesses of each method and made the necessary adjustments to make the data comparable," summarized Enrico Mattea, a researcher in the Department of Geosciences at the University of Fribourg, for ATS.

According to the members of the GlaMBIE project, "our results provide a more accurate baseline, essential for better understanding differences in observation and calibrating models. This advance will help reduce uncertainty in projections for the 21st century."

Published in the journal "Nature", their study does not merely improve monitoring of glacier evolution: it also offers a refined view of their transformation over the past two decades (2000-2023).

Here are some key elements:

1️⃣

Limits of previous models: Essential components of the climate and terrestrial hydrological system, glaciers require rigorous monitoring to better understand, assess and, if possible, mitigate ongoing climate change. For years, scientists have relied on four main observation methods: glaciological measurements, comparisons of digital elevation models (DEMs), altimetry, and gravimetry.

"The heterogeneity of these methods in terms of spatial coverage, temporal resolution and observational accuracy, combined with the diversity of approaches within a single method and the lack of harmonization, has called into question past assessments of glacier mass changes," warn the members of the GlaMBIE project.

2️⃣

Scientific assessment and refined methodology: Still relying on the four classic observation methods, the scientists conducted a five-step analysis across 19 predefined regions. Some 450 contributors, organized into 35 research teams, compiled 233 estimates of regional glacier mass changes, covering a period beginning in the early 2000s.

"Thanks to this approach, GlaMBIE provides a homogenized time series of annual mass changes at regional and global scales from 2000 to 2023. This harmonization accounts for spatial, temporal and methodological differences, as well as changes in the area of regional glaciers," the researchers explain.

According to them, this work allows a more accurate global assessment of glacier transformation, thus forming a solid foundation for future research.

3️⃣

Comparison with the IPCC study: As a concrete example, GlaMBIE analyzed the IPCC assessment reports, revealing some discrepancies, notably concerning regional glacier mass changes. "For the periphery of Greenland as well as for the Antarctic and subantarctic islands, our estimate is less negative than that reported in the Sixth IPCC Assessment Report," the study specifies.

One of the most striking aspects of this collaborative work lies in the analysis of emission scenarios and their consequences for glaciers. "Overall, our observations as well as recent modeling studies indicate a greater glacier mass loss than that estimated in the Sixth IPCC Assessment Report. We are therefore facing a continuing, even accelerating, reduction in glacier mass through the end of the century."

4️⃣

Acceleration confirmed: "Not surprisingly, the last five years have been marked by a notable acceleration of melting, with a record loss of 548 gigatonnes of mass in 2023," observes Enrico Mattea. According to this researcher in the Department of Geosciences at the University of Fribourg, "glacier mass loss proves to be up to twice as large as that of the Greenland and Antarctic ice sheets."

The study reveals that Alaska's glaciers have lost 22% of their mass, while those in the Canadian Arctic recorded a 20% decrease. However, the largest losses concern regions where glacier area is smaller (less than 15,000 km²), such as Central Europe (-39%), the Caucasus (-35%) and New Zealand (-29%).

"The comparison of regional rates of change between the first (2000-2011) and the second (2012-2023) halves of the record highlights increased mass loss in 14 of the 19 regions," specifies GlaMBIE.

This vast work of data harmonization constitutes a further advance in understanding climate evolution. The first conclusions of GlaMBIE should prompt the world's major powers to deep reflection. Yet the reality is quite different: in recent days, we have witnessed the first political dissensions around the IPCC and the publication of its seventh report.

This article has been automatically translated using AI. If you notice any errors, please don't hesitate to contact us.

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