Glacier Melting Speed Has Doubled in the Past Two Decades

ON 04/28/2021 AT 08:55 PM

A new paper has revealed glacier melting tied to global heating has increased by almost 2X in the last 20 years. That puts it way ahead of melting of ice sheets in Greenland and Antarctica as a global contributor to sea level rise.

Kenai Glacier

The Kenai glacier in Alaska is one of many in the region which together has put Alaska at the top of the list of regions for the highest amount of ice loss during the last 20 years. Photo: Pixabay

The paper, written by an international team of researchers, was published in the April 28, 2021, issue of Nature.

The conclusion that the myriad of glaciers which make up a major part of the global cryosphere is now releasing enough water into waterways, lakes, rivers, and eventually the oceans to raise sea levels more than Greenland and Antarctica combined is a shock.

According to the study, glaciers around the world shed an average 267 gigatons (Gt) of ice per year during the period from 2000-2019. That is a rate almost twice that of previous years.

For those twenty years, that amounts to 5,340 Gt of accumulated ice melt which has already mostly seeped into the ocean. As a reference, the scientists who prepared the article pointed out the amount of glacial water sliding into the world’s oceans during that time was the equivalent of flooding the entire surface of United Kingdom to a depth of ~2 meters of water every year.

By comparison, climate crisis-induced melting of Greenland’s massive ice sheet contributed just 68% of that total amount of water during the same period. The shrinking of the majestic ice sheets of Antarctica also contributed far less, at a rate only around 50% of what the total of all glacial melting produced.

The authors pulled together this data through satellite and other measurements of 217,175 separate glaciers, using measurements of elevation changes over those periods. Those glaciers include the 200,000 square kilometers of glaciers amidst the Antarctic and Subantarctic seas, and the Greenland periphery glaciers that are not on Greenland itself.

According to the study, the top 6 major glacier contributors to the total 267 gigatons of melt per year are in Alaska, the Greenland periphery, Northern Canada, the Antarctic and Sub-Antarctic Ice sheets, the Southern Andes, and Iceland. Alaska alone contributed to one-fourth of the total mass loss of glaciers.

Glacier Ice Mass Loss Regional Rankings

Ranking of the top six regions of the world for glacier ice melt for the years 2000-2019, based on data from the authors' paper, "Accelerated global glacier mass loss in the early 21st Century." Photo: Climate Survival Solutions Graphic, from data provided in the paper.

Not depicted in this chart were the Himalayas and high-altitude Asian regions. Together they contributed to 8% of the total ice mass loss during the 2000-2019 period.

Besides the surprise that glaciers generally were contributing far more strongly to sea level rise than the usual suspects of Greenland and Antarctica, the study also revealed that smaller glacier ranges were being impacted more rapidly than others during this period. While total glacier melt in 2019 was twice what it was in 2000, for New Zealand the increase was a rate about 7X what it was at the beginning of the 21st century.

Romain Hugonnet, the lead author of the study and a professor at the University of Toulouse, said the data suggests an accelerating danger to the planet.

“A doubling of the thinning rates in 20 years for glaciers outside Greenland and Antarctica tells us we need to change the way we live. We need to act now,” he explained in an interview soon after the paper was released. “It can be difficult to get the public to understand why glaciers are important because they seem so remote, but they affect many things in the global water cycle including regional hydrology, and by changing too rapidly, can lead to the alteration or collapse of downstream ecosystems.”

As to the future, Hugonnet was greatly concerned. Using the example of the Swiss Alps near where he lives, he said, “The glaciers in the Alps are not thick and are [some of the] fastest melting in the world. That will continue until there is nothing left. How fast depends on different climate scenarios, but at current speed, 80-90% will be gone by 2050. That means we will lose almost everything, except the biggest glaciers.”

Hugonnet’s warnings about the Alps are not the only ones. In the Himalayan glacial regions where even Mount Everest is now being exposed, countries such as Nepal and Bhutan are reporting glacial melting having already occurred at a rate that downstream hydroelectric power systems, which depend on such melts for water flow to generate clean electricity, are even now producing less power than in the past as there is less ice left to provide such fresh water.

The combination of sea level rise plus an absolute decrease in available water flow from glaciers globally points to an immediate need for policymakers to plan for drastic changes to how everything from power generation to agriculture and drinking water supplies must be managed.

In Asia in particular, the past approach of assuming unlimited supplies of water is rapidly depleting aquifer resources in countries as far apart as India and the Philippines. These countries and others in the region, including in the Mekong Delta where Vietnam, Laos, and Cambodia are suffering water losses as well, are now dealing with the repercussions of decades of mismanagement of those supplies for use in hydroelectric power generation, agricultural use, and drinking water supplies. These issues, now multiplied manyfold by decades of global heating, has created a global disaster in the making, especially as governments are ignoring the situation.

Lead author Hugonnet’s statements strongly support these conclusions.

“India and China are depleting underground sources and relying on river water, which substantially originates from glaciers during times of drought,” he said recently in further comments about his group’s study. “This will be fine for a few decades because glaciers will keep melting and provide more river runoff, which acts as a buffer to protect populations from water stress. But after these decades, the situation could go downhill. If we do not plan ahead, there could be a crisis for water and food, affecting the most vulnerable.”