Operation IceBridge - Greenland Glaciers
Greenland’s more than 200 major outlet glaciers are constantly on the move, most of them draining ice from the central ice sheet. Jakobshavn is Greenland’s fastest-moving glacier, and the flow rate is variable with spurts of speed in the summer and additional variation from year to year.
When an ice tongue such as the Jakobshavn calves, the glacier feeding that ice tongue typically accelerates. Reduced friction between the intact glacier and the bedrock, and reduced buoyancy from the seawater (which partially offsets the glacier’s downhill flow) mean less resistance to glacier movement. Warming conditions in the Arctic contribute to glacier acceleration in multiple ways. Warmer conditions can send meltwater to the glacier’s base, increasing lubrication and consequently glacier speed. During the winter, the rate of iceberg calving usually slows significantly; the glacier tongue advances, and its flow speed drops. Warm winters, however, may allow iceberg calving and high flow rates to continue.
Since 2000, Greenland has lost some 739 gigatons of ice, and approximately 30 percent of that loss came from Jakobshavn and four other glaciers