Evans Ice Stream

Evans Ice Stream
Name	Evans Ice Stream
Location	West Antarctica
Coordinates	75, 0, S, 105...
Length	~80 km
Width	~20 km
Thickness	~1,000 m
Status	Active

Evans Ice Stream. It is a significant glacier located in West Antarctica, flowing into the Amundsen Sea. This ice stream is a major component of the West Antarctic Ice Sheet, contributing to the dynamics and mass balance of the region. Its behavior is closely monitored due to its potential impact on global sea level rise.

Geography and Location

The Evans Ice Stream is situated within Marie Byrd Land, a remote region of West Antarctica. It originates from the interior of the West Antarctic Ice Sheet and drains westward into the Amundsen Sea Embayment. Its terminus is near the Pine Island Bay, adjacent to other major outlets like the Pine Island Glacier and the Thwaites Glacier. The surrounding area is characterized by deep subglacial basins, including the Pine Island Trough, which guides its flow. The ice stream is bounded by the Hudson Mountains to the north and the Crary Mountains to the south, with its catchment area feeding into the Amundsen Sea.

Physical Characteristics

The Evans Ice Stream is approximately 80 kilometers long and 20 kilometers wide, with an ice thickness averaging around 1,000 meters. It features a relatively fast-flowing central trunk, with surface velocities exceeding several hundred meters per year. The bed topography beneath it is deep and below sea level, making it susceptible to marine ice sheet instability. Its surface is marked by extensive crevassing and shear margins where it meets slower-moving ice. The subglacial geology includes sedimentary basins and bedrock highs that influence its flow pathways.

Discovery and Naming

The ice stream was identified and mapped during aerial surveys conducted by the United States Geological Survey in the 1960s and 1970s. It was named by the Advisory Committee on Antarctic Names in honor of Edward Evans, 1st Baron Mountevans, a British naval officer and Antarctic explorer who served under Robert Falcon Scott on the Terra Nova Expedition. The naming followed the conventions of the United States Board on Geographic Names and was officially adopted after the completion of detailed reconnaissance by the British Antarctic Survey and other international programs.

Dynamics and Flow

The flow of Evans Ice Stream is primarily driven by basal sliding and deformation of soft subglacial sediments. It exhibits a typical flow pattern for Antarctic ice streams, with rapid motion facilitated by a lubricating layer of water-saturated till at its base. Observations from satellite missions like NASA's ICESat and the European Space Agency's CryoSat-2 have recorded seasonal and interannual variations in its velocity. Its dynamics are sensitive to changes in ocean temperature, particularly influxes of Circumpolar Deep Water into the Amundsen Sea. Interaction with the Pine Island Glacier system also influences its strain rates and mass flux.

Role in the West Antarctic Ice Sheet

The Evans Ice Stream is a key contributor to the mass loss from the West Antarctic Ice Sheet, which holds enough ice to raise global sea level by several meters. It acts as a drainage conduit, channeling ice from the vast interior reservoirs of Marie Byrd Land into the ocean. Its stability is interlinked with the broader Amundsen Sea Embayment sector, where accelerated retreat has been observed since the late 20th century. Studies led by institutions like the British Antarctic Survey and NASA's Operation IceBridge indicate it plays a crucial role in potential scenarios of marine ice sheet instability.

Scientific Research and Exploration

Scientific investigation of the Evans Ice Stream has intensified since the 1990s, utilizing ice-penetrating radar, seismic surveys, and autonomous sensors. Major projects include the West Antarctic Ice Sheet Initiative and the International Thwaites Glacier Collaboration. Research stations like the British Antarctic Survey's Rothera Research Station and the United States Antarctic Program's McMurdo Station support field campaigns. Key findings have been published in journals such as Nature (journal) and Science (journal), focusing on its basal hydrology, grounding line retreat, and contributions to sea level rise.

Category:Glaciers of West Antarctica Category:Marie Byrd Land