Longest supraglacial river

The melting of glaciers each summer often produces large volumes of water that create rivers incised into the ice. Some of the longest rivers form on the huge polar ice sheets in Greenland and Antarctica. The longest supraglacial river in Greenland forms annually on Nioghalvfjerdsbræ (or 79°N Glacier) and has been measured at 81 kilometres (50 miles) long. However, the world’s longest supraglacial river was observed on a satellite image of the Amery Ice Shelf in East Antarctica captured on 22 January 2015, where a network of interconnected streams transported water over a distance of 120 kilometres (75 miles). The findings were published in Nature on 20 April 2017.

This makes it almost four times longer than the River Onyx, which is the longest terrestrial river in Antarctica and flows westward for 32 km (20 mi) along the Wright Valley in the Transantarctic Mountains.

The longest river in Antarctica, however, flows under the ice sheet, where a meltwater pathway has been identified that is 460 km (286 mi) long. It is the world's longest subglacial river.