World's mountain glaciers may hold 20% less ice than thought
The world’s glaciers may contain less ice volume than previously thought, according to a study published in Nature Geoscience, meaning their potential contribution to water supplies would be lower than older estimates.
Why it matters: Glaciers around the world are rapidly melting because of global warming from human-caused greenhouse gas emissions. Their melting frees up water that raises global sea levels, and provides water supplies to people at lower elevations.
- While the study would suggest that global sea level rise could also be less than estimated, glacial melt is just one factor that contributes to rising oceans. The vast majority of sea level rise is coming from the world's polar ice sheets in Greenland and Antarctica, as well as the thermal expansion as ocean waters warm.
By the numbers: The researchers generated an estimate of total global ice volume by mapping 98% of the worldwide glacier-covered area using hundreds of thousands of satellite images collected between 2017 and 2018.
- They determined that the world’s glaciers can potentially contribute roughly 257mm (10 inches) to sea-level rise, or around 20% less than previously estimated.
They also found regional distinctions in ice volume compared to previous assessments. For example, they estimate that the Himalayas at that time held 37% more ice than past surveys found, while the Andes in South America contained 27% less.
- Those new corrections in ice volume can clarify how much freshwater is available to people living near those glaciers and can inform governmental decisions on infrastructure and agricultural reforms.
- For example, hundreds of millions of people living in multiple countries rely on the Himalayan glacier- and snow-fed Indus, Ganges and Brahmaputra rivers for freshwater.
The big picture: Though their estimate suggests that glacial melt may contribute less water to sea-level rise than previously expected, the researchers said their study cannot make projections on the total rise because thermal expansion and shrinking ice sheets are the biggest factors.
- The U.N. Intergovernmental Panel on Climate Change warned last year that glaciers capping three of Africa's iconic mountains — Mount Kenya in Kenya, the Rwenzori Mountains in Uganda and Mount Kilimanjaro in Tanzania — will likely disappear over the next two decades.
- Illustrating the high stakes involved with melting ice sheets, scientists are currently studying a massive glacier in West Antarctica — nicknamed "The Doomsday Glacier" — that could drastically raise sea levels by melting over the next several decades to centuries, Axios' Andrew Freedman reports.
Go deeper: New metric shows how severe global warming is getting