Erick Burgueño Salas
Research expert covering climate change and the water industry
Melting glaciers and sea ice - statistics & facts
Glaciers and sea ice are melting at an alarming rate, driven primarily by climate change. The melting of these bodies of ice is linked to several issues already impacting the planet, including rising sea levels, endangered wildlife, thawing permafrost, and intensifying heat waves. In turn, the accelerating loss of land and sea ice is likely to aggravate climate change further, in a feedback loop set to pose significant challenges to humanity in the future.
This is part of a series on the effects of climate change.
Sea ice, on the other hand, forms entirely in the ocean when seawater freezes and floats on the ocean surface. The average global sea ice extent has diminished over the past four decades, with Arctic sea ice disappearing at a far greater rate. In September 2020, the average sea ice extent in the Northern Hemisphere reached a record-low of four million square kilometers, down from almost eight million square kilometers in September 1980. Meanwhile, the sea ice extent in the Southern Hemisphere dropped abruptly below 18 million kilometers in September 2023 for the first time since records began, despite having shown no signs of significant disturbance in previous years.
The outlook for glaciers and sea ice and all the organisms that depend on them is dire. Even if warming is limited to 1.5 degrees Celsius, in accordance with the Paris Agreement’s target, it is forecast that half of global glacial mass will be lost by 2100, aggravating climate change further.
This is part of a series on the effects of climate change.
How fast are glaciers and sea ice melting?
Glaciers and sea ice are part of the Earth’s cryosphere, which is the portion of the planet’s surface where water exists in solid form. Although somewhat similar, they differ in several ways. Glaciers are formed on land when accumulated snow is compressed over many years, forming layers of ice that are constantly moving under their weight. From the Southern Andes to the Himalayas, glaciers are retreating around the world at increasing rates. Between 1970 and 2023, approximately 26 metric tons of ice per square meter have been lost worldwide. In the hydrological year 2020/21 alone, glaciers in Western North America lost more than 1.7 metric tons of ice per square meter, making it the region with the worst glacial mass balance. No glacial region reported positive mass balances in that year.Sea ice, on the other hand, forms entirely in the ocean when seawater freezes and floats on the ocean surface. The average global sea ice extent has diminished over the past four decades, with Arctic sea ice disappearing at a far greater rate. In September 2020, the average sea ice extent in the Northern Hemisphere reached a record-low of four million square kilometers, down from almost eight million square kilometers in September 1980. Meanwhile, the sea ice extent in the Southern Hemisphere dropped abruptly below 18 million kilometers in September 2023 for the first time since records began, despite having shown no signs of significant disturbance in previous years.
The effects of melting
Sea ice plays a crucial role in regulating the global climate as its large, bright surfaces reflect sunlight back into space, helping to keep the planet cooler. When the surface area becomes smaller, less heat is reflected, and more heat is absorbed at the surface. This results in warmer temperatures that, in turn, worsen melting. Melting sea ice also represents a threat to the wildlife that depends on it, such as polar bears and walruses. On land, the melting of glaciers and ice sheets critically impacts sea level. Under a two degrees Celsius warming scenario, melting glaciers across the world are forecast to cause a sea level rise of 99 millimeters by 2100. The melting glaciers of Alaska are projected to contribute the most, with around 22 percent of the sea level rise.The outlook for glaciers and sea ice and all the organisms that depend on them is dire. Even if warming is limited to 1.5 degrees Celsius, in accordance with the Paris Agreement’s target, it is forecast that half of global glacial mass will be lost by 2100, aggravating climate change further.
