Glaciers are massive bodies of ice that form over thousands of years from compacted snow. They cover about 10% of the Earth's land surface and store about 69% of the world's freshwater.
Glaciers are also sensitive indicators of climate change, as they respond to changes in temperature and precipitation. However, glaciers are not only affected by climate change, they also affect it.
As glaciers melt, they contribute to sea level rise, alter regional hydrology, and influence global energy balance.
What is Glacier Loss Day and why is it important?
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Glacier Loss Day (GLD) is a concept proposed by a team of glaciologists from the University of Innsbruck, Austria, to measure the annual mass balance of glaciers.
Mass balance is the difference between the amount of snow and ice that accumulates on a glacier and the amount that melts or sublimates.
A positive mass balance means that a glacier is growing, while a negative mass balance means that it is shrinking.
The researchers used a terrestrial laser scanner to monitor the daily changes in volume and surface elevation of the Hintereisferner, one of the largest and best-studied glaciers in the Alps.
They defined GLD as the day when the glacier loses all the mass it gained during the previous winter.
GLD can be compared to Earth Overshoot Day, which marks the date when humanity's demand for ecological resources exceeds what the planet can regenerate in a year.
GLD is important because it provides a simple and clear way to communicate the state and fate of glaciers to the public and policymakers.
It also helps to assess the impact of climate change on glaciers and their downstream ecosystems and communities.
By tracking GLD over time, we can see how fast glaciers are losing mass and how much time they have left before they disappear completely.
How is GLD changing and what are the consequences?
According to the study published in The Cryosphere, GLD has been advancing earlier in the year since 2016, indicating an accelerated melting of the Hintereisferner.
In 2022, GLD was reached on June 23, which was the earliest date ever recorded.
In comparison, GLD was reached in mid-August in 2020 and 2021, and in late July in 2003 and 2018, which were also years with extreme negative mass balance.
The researchers estimated that the Hintereisferner lost about 13% of its volume between 2016 and 2022, which is equivalent to filling more than 400 Olympic-sized swimming pools with water.
They also projected that if the current trend continues, GLD could occur as early as May by 2035, meaning that the glacier would have no chance to recover during the summer.
The implications of GLD advancing are dire for both the glacier itself and its surrounding environment.
As the glacier melts, it exposes more dark rocks and debris that absorb more solar radiation than snow and ice, creating a positive feedback loop that enhances melting.
As the glacier retreats, it also reduces its influence on the local climate, such as cooling the air and increasing precipitation.
Moreover, as the glacier shrinks, it affects the availability and quality of water for irrigation, drinking, hydropower, and recreation.
Finally, as the glacier disappears, it threatens the biodiversity and cultural heritage that depend on it.
