jökulbráðnun

Jökulbráðnun, Icelandic for glacial melt, is the process by which glaciers lose mass through melting and related mechanisms. It includes surface melt, basal melt, calving of ice to form icebergs, and sublimation at high elevations. Jökulbráðnun reduces glacier volume and can alter flow dynamics and glacier geometry.

Causes are driven primarily by rising air temperatures and ocean warming, consequences of anthropogenic climate change. Local factors such as debris cover and albedo changes from dust and soot can accelerate melt, while precipitation patterns and seasonal cycles influence the balance between accumulation and ablation.

Impacts include contributions to global sea level rise, changes in freshwater availability, and altered river discharge. Meltwater reshapes downstream ecosystems, increases sediment transport, and can pose hazards in mountainous terrain, including glacial outburst floods (jökulhlaups) in regions with volcanic or geothermal activity and infrastructure exposure.

Monitoring uses glacier mass-balance measurements, river discharge data, and satellite observations to track retreat and thinning. Globally, most glaciers have exhibited negative mass balance and shrinking volume since the 19th century, with acceleration in the late 20th and early 21st centuries. Regions with pronounced retreat include the European Alps, Andes, Himalayas, Alaska, and Patagonia.

In Iceland, jökulbráðnun has particular significance as many glaciers have retreated markedly since the early 20th century, affecting glacial rivers and the frequency of jökulhlaups. Projections under warmer scenarios indicate continued loss of glacier ice, with implications for water resources, ecosystems, and natural-hazard management.