Study of “Decreased” Ice Volume Largely a Matter of Relabeling Glaciers as Ice Sheets

Nature Geoscience, 7 February 2022

Widespread media coverage of this study unfortunately has resulted in a mischaracterization of its main conclusions, by claiming that the world’s glaciers “hold 20% less ice than previously estimated.” In reality, their estimate of global glacier volume excludes huge areas of Antarctica that were included in previous estimates. The ice they excluded is not gone; it was simply relabeled as “ice sheet” rather than “glacier.” This is a common issue with both Greenland and Antarctica: some scientists count as “glaciers” only those ice masses not physically connected to the main Greenland or Antarctic ice sheet; others use different criteria. This study took the more conservative view for Antarctica and considered many large ice masses on islands surrounding the mainland to belong to the ice sheet; hence the 20% “decrease” reported in most media.

Otherwise, this study uses an interesting new satellite mapping technique to estimate the thickness of glaciers based on their speed. At a regional level, it provides an appropriate assessment of not only glacier volume, but future freshwater availability. In particular, this study suggests that four million people living near the Andes mountains of South America will reach “peak water” – the point where meltwater runoff from glacier ice loss in a warming climate, followed by declining seasonal availability of water as the glacier disappears – much sooner than expected. These Andean glaciers contain one-fourth less ice than previously estimated, jeopardizing freshwater resources for local populations. This study highlights the importance of rapid action to curb global emissions and protect those who live on the frontlines of climate change in glacier-dependent regions, estimated at 3 billion globally.