above sea level, a range which, as noted by Dyurgerov (2002), is exceeded only by Devon Ice Cap in the world list of glaciers with measured mass balance. Ice thickness reaches or exceeds . Its maximum extension in recent history, marking the advance of the glacier in response to the cooling of the Little Ice Age, was reached not earlier than the late 18th century, and more probably at the beginning of the 20th century. There is evidence that the retreat of the terminus, previously at about per year, is decelerating (Cogley et al. 1996a; Cogley and Adams 2000). White Glacier has been the subject of many papers in the glaciological literature since 1960, e.g. Müller (1962) was the source of a now-classical diagram elaborating and illustrating the concept of "glacier facies". Population The island is uninhabited except for the seasonal McGill Arctic Research Station operated by McGill University. Lost Hammer Spring The Lost Hammer Spring, located in the central west region of the island () is the coldest and saltiest of all Arctic springs described to date. It is characterized by a perennial hypersaline (24%) discharge at subzero temperatures (~) flowing to the surface through a hollow, high cone-shaped salt tufa structure. Continuous gas emissions from the spring indicate an underlying thermogenic methane source. On the basis of these properties, this spring is considered a significant astrobiology analogue site for possible habitats currently present on Mars and the cold moons Europa and Enceladus. Microbes have been found at this site which do not depend on organic material or oxygen, but only on simple inorganic compounds. These inorganic compounds are present on Mars. Views of the island See also Ellesmere Island Volcanics References Further reading Chih-Ying Lay, Nadia C. S. Mykytczuk, Étienne Yergeau, Guillaume Lamarche-Gagnon, Charles W. Greer, & Lyle G. Whyte, "Defining the Functional Potential and Active Community Members of a Sediment Microbial Community in a High-Arctic Hypersaline Subzero Spring," Applied and Environmental Microbiology, Volume 79 Number 12 (June 2013), p. 3637–3648. http://aem.asm.org/content/79/12/3637 External links Axel Heiberg Island in the Atlas of Canada - Toporama; Natural Resources Canada Axel Heiberg Island's Eocene forests Unearthing a Frozen Forest Arctic Redwood Fossils Are Clues to Ancient Climates Islands of the Queen Elizabeth Islands Sverdrup Islands Uninhabited islands of Qikiqtaaluk Region