The Arctic landscape is changing at an unprecedented rate. In addition to rising temperatures, climate change is causing episodes of extreme melting, which occurs when ice losses that previously took weeks or months occur over just a few days. These increasingly frequent events are altering the normal dynamics of ice loss. They are profoundly changing the state of snow and ice, which are the most vulnerable elements of the polar climate system. Snow accumulation during winter no longer compensates for summer losses. This annual balance has been negative for decades, but extreme episodes, which can last for days or weeks, cause much higher melting rates than usual. These are heat waves defined not by air temperature, but by high melting rates that cause snow and ice to disappear. The Arctic is melting What was once exceptional is now occurring with increasing regularity. This pattern is observed throughout the Arctic, but there are significant regional differences. The highest rates of extreme melting are recorded in northwestern and northern Greenland, as well as on Ellesmere and Devon Islands in the Canadian Arctic. In contrast, the eastern Arctic – which includes Iceland and Russia’s Novaya Zemlya archipelago – shows smaller increases. Greenland has been most severely impacted. It is home to the largest ice reserve in the northern hemisphere, which holds enough water to raise sea levels by more than seven metres, and its geographical location makes it particularly sensitive to atmospheric patterns that trigger extreme melting. Recent summers in Greenland have seen some of the most intense episodes ever documented – in July 2012, August 2019, and August 2021, more than 90% of its surface was simultaneously in a state of melting, in some cases surpassing paleoclimatic records. Read more: Greenland’s melting ice caps reveal the true extent of climate change Why are these extreme events happening? These episodes are triggered when general warming in the Arctic combines with atmospheric patterns that can intensify melting. The gradual rise in temperatures sets the stage, but it is specific weather patterns, such as prolonged blocking anticyclones, that turn a hot summer into an extreme event. Blocking anticyclones occur when an area of high pressure remains stationary for several days, diverting normal weather systems. This causes atmospheric stability and clear skies, allowing warm air from the south to rapidly raise surface temperatures. In some cases, the arrival of masses of humid air generates warm clouds that radiate heat towards the ice, further accelerating melting. These blocks have become more frequent and longer lasting, making it likely that the these weather systems will reoccur. Each episode also leaves a physical mark on the ground, as melting removes recent snow and exposes darker, less reflective ice. This decrease in reflected sunlight, known as albedo, intensifies the absorption of solar energy, causing the next melt to act on a more vulnerable surface. This causes a feedback loop that accelerates mass loss and contributes to the rapid warming that now characterises the Arctic. Furthermore, since around the 1990s, summer melting has intensified and spread to high-altitude areas that historically remained below freezing throughout the summer. Today, the isotherm (the line indicating the altitude at which the temperature is 0 °C is rising higher and higher, shifting the melting zone deeper into glaciers and reducing the size of areas that previously acted as accumulation reservoirs. Read more: Arctic Ocean: climate change is flooding the remote north with light – and new species The consequences of extreme melting Extreme melting has immediate effects on glaciers, but its consequences extend beyond the polar regions. Locally, it restructures snow, weakens the ice surface and generates runoff that can mobilise large volumes of water in a very short time. This surface water accelerates melting and ends up flowing into the ocean as a concentrated surge of fresh water. On a global scale, the impact is also significant. The Arctic acts as a key climate regulator, as its white surface reflects a lot of solar radiation. When Arctic ice disappears, that capacity is reduced and the region absorbs more heat, amplifying warming. Extreme events intensify this effect by darkening the surface and accelerating ice loss. In addition, the influx of fresh water into the North Atlantic directly contributes to sea level rise, alters ocean salinity, and may affect the Atlantic Meridional Overturning Circulation (AMOC), a sea current that is fundamental for climate stability in Europe and other regions. Extreme melting is not just a polar phenomenon – it affects the entire planet, and connects the fate of the Arctic with the world’s environmental balance. A weekly e-mail in English featuring expertise from scholars and researchers. It provides an introduction to the diversity of research coming out of the continent and considers some of the key issues facing European countries. Get the newsletter!
Extreme melting episodes are accelerating ice loss in the Arctic
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