Jakobshavn Isbræ, also known as the Jakobshavn Glacier and Sermeq Kujalleq (in Greenlandic) is a large outlet glacier in West Greenland. It is located next to the Greenlandic town of Ilulissat (Danish: Jakobshavn) at the Ilulissat Icefjord, approximately at 69°10′N, 49°50′W.
Jakobshavn Isbræ is a major contributor to the mass balance of the Greenland ice sheet, producing some 10% of all Greenland icebergs. Some 35 billion tonnes of icebergs calve off and pass out of the fjord every year. Icebergs breaking from the glacier are often so large (up to a kilometer in height) that they are too tall to float down the fjord and lie stuck on the bottom of its shallower areas, sometimes for years, until they are broken up by the force of the glacier and icebergs further up the fjord. Studied for over 250 years, Jakobshavn Isbræ has helped develop our understanding of climate change and icecap glaciology.
It is also one of the fastest moving glaciers, flowing at its terminus at speeds of 20 to 22 metres per day. The rate has accelerated in recent years, probably due to global warming. The ice stream's speed-up and near-doubling of ice flow from land into the ocean has increased the rate of sea level rise by about .06 millimeters (about .002 inches) per year, or roughly 4 percent of the 20th century rate of sea level rise.