C. H. Ostenfeld Glacier () is one of the major glaciers in northern Greenland, originating from the Greenland Ice Sheet. Its catchment area covers nearly 14 500 km<sup>2</sup>, or about 1.2% of GreenlandâÂÂs entire ice sheet surface. If all that ice were to melt, it would raise global sea levels by an estimated 3.9 centimeters.
This glacier was first mapped by Lauge Koch in 1917 during Knud Rasmussen's 1916-1918 Second Thule Expedition to north Greenland and was named after Danish botanist Carl Hansen Ostenfeld (1873âÂÂ1931), author of Flora of Greenland and its origin.
The C. H. Ostenfeld Glacier originates from the North-Central sector of the Greenland Ice Sheet, at around 81.6 N, 45.2W. It is roughly southeastâÂÂnorthwest oriented and drains into Victoria Fjord, moving about 2.3 cubic kilometers of ice into the ocean each year â making it the largest single contributor to the total ice and freshwater discharge to the fjord. Ice at the glacierâÂÂs grounding line, where the glacier ice meets the fjord's seawater and forms a floating ice tongue, flows at about 770âÂÂ800 meters per year, a speed comparable to other nearby giants such as Ryder and Petermann Glaciers.
The glacier terminus is characterised by the presence of three nunataks close to the grounding line. Two smaller glaciers, Harder and Brikkerne Glaciers, also drain into Victoria Fjord near C. H. Ostenfeld Glacier. Though they originate from a separate dome of ice, their tongues once merged with C. H. Ostenfeld's, effectively creating a shared floating front.
Although the C.H. Ostenfeld Glacier is one of North GreenlandâÂÂs major outlets in both size and ice flow, its past behavior is still poorly understood. Its remote location has made long-term monitoring extremely difficult, and most of current knowledge comes from satellite images collected only in recent decades. These modern observations reveal a glacier that has not changed steadily, but rather has alternated between periods of advance and retreat. Remarkably, there is significant scientific disagreement with regards to the magnitude of frontal position shifts over time. This uncertainty likely stems from the glacierâÂÂs ice tongue's heavily fractured surface, which makes it difficult to pinpoint the true edge of the ice front.
Aerial photographs from the late 1970s show that the glacier floating ice tongue was once stretching more than 25 kilometers into the fjord. This configuration dramatically changed in the early 2000s, when the ice tongue collapsed. In 2003 alone, C. H. Ostenfeld glacier lost about 80% of its floating extension, amounting to a total loss of roughly 27 cubic kilometers of ice compared to 1978. This was one of the earliest abrupt ice tongue collapses ever observed in North Greenland.