During the period 2000-2019, the mass of the world’s glaciers decreased by an average of 267 billion tons per year, which is a new figure. A study published in Nature. Mass loss, i.e. the reduction in the amount of snow and ice that make up the glaciers, is roughly twenty times the size of Lake Mälaren.
The rate of melt increased by 48 billion tons per year over the same period, a volume corresponding to approximately 3.5 billion tons.
The study is important to understand the impact of climate on glaciers in mountainous environments. There’s often a lot of focus on Greenland and Antarctica, and you might forget how important ice and snow are in the frigid parts of the mountain regions, says Mats Erickson, a water and climate expert at the Stockholm International Water Institute, SIWI.
In this study, researchers mapped changes in more than 200,000 glaciers, and nearly all of the glaciers on Earth.
Glaciers have one Critical for both sea level rise and water supply. And their breakdown is the second biggest reason for this Sea levels are risingThe biggest thermal expansion is that warmer water takes up more space than cold water. It is also one of the water tanks most sensitive to climate.
Climate change means that about 200 million people live on land that is estimated to be under water due to sea level rise by the end of the century. more than One billion people are at risk Suffering from water shortages within the next 30 years, according to a United Nations report.
At the same time because they are of great importance to the global water cycle and human life, glaciers belong to the regions about which there is the least amount of knowledge. Only a few hundred of all the glaciers in the world have been studied at the site by scientists. The lack of research and knowledge gaps were cited, among other things, in the latest IPCC Special Report on Oceans, Cryosphere, and Frozen Areas on Earth.
It’s very difficult to get an overview of the more than 200,000 glaciers that exist around the world. Mats Erickson says they’re scattered in a way that’s hard to understand, often in an inaccessible environment.
According to the new study, melting glaciers account for a fifth, 21 percent, of the measured sea level rise over the period 2000-2019. It accounts for between 6 and 19 percent, with an estimated average of 9 percent, of the increased rate of sea level rise observed during this period.
Seven glaciers It accounts for 83 percent of the total collective loss. These are Alaska, the coastal glaciers of Greenland, two regions in the Canadian Arctic, Antarctica, and the Himalayas including Tibet and the Southern Andes.
– Alaska stands out. There, the drop is massive and accounts for a quarter of the global mass loss. One of the reasons cited, Mats Erikson says, is because there has been some precipitation and hence the glaciers are not built on.
It is also clear that there are very big differences in different regions of the world. And it is very important to understand that you cannot drag all glaciers over a hill when it comes to how climate affects them.
Regional differences are related to changes in temperature and precipitation between different decades. In parts of the region around the North Atlantic, melt slowed during the 2000s and at the same time increased sharply in glaciers in northwest America. Alaska, northwest Canada, and the United States account for nearly half of the mounting mass losses.
In Karakoram, a district of Pakistan Which has the highest mountains in the world, glaciers have not previously lost their mass despite global warming, they have increased. But now those glaciers have diminished, too.
One of the theories that explains why glaciers have not melted there before is that when the temperature rises, there is more moisture in the atmosphere which leads to more precipitation in the form of snow as long as the temperature is below zero degrees. The rainy season in Karakoram is during winter, so the glaciers have been supplemented with snow and ice. To the east in the Himalayas, the rainy season is in spring and summer.
Although differences in precipitation over several decades explain some of the regional deviations measured, the researchers note that the increase in glacier mass loss reflects global warming.
The report states The speed has also nearly doubled in terms of glaciers thinning, excluding those that reach the coast, from 0.36 meters per year in 2000 to 0.69 meters per year in 2019.
Mats Erickson says the whole development is worrying.