cryosphere glossary- universityof hawaii（cryosphere universityof hawaii glossary -）.doc

Lab: Vostok Ice Core Map showing Antarctica and location of Vostok Ice Core. Colors indicate elevation. I. Introduction Snow falling in the polar regions of the earth (e.g. Greenland and Antarctica) sometimes is preserved as annual layers within the ice sheets, provided that they are not destroyed by flow of the ice. These annual layers provide a record of the earths climate that reaches back as much as 200,000 years. Several different climate indicators can be measured from samples of the ice: The amount of dust in each annual layer is indicative of the environment at the time that the dust was deposited. Various kinds of fallout from the atmosphere, including airborne continental dust and biological material, volcanic debris, sea salts, cosmic particles, and isotopes produced by cosmic radiation, are deposited on the ice sheet surface along with the snow, thus mixing with the snow and also acting as a distinctive barrier between different ice layers. The composition of bubbles of air trapped in the ice is a measure of the composition of the atmosphere in ancient times. With increasing pressure from subsequent snow deposition on an ice cap or glacier, the snow becomes compacted and, consequently, air is trapped within the deposited layer. This entrapment of air occurs essentially with no differentiation of the atmospheric gas components. However, carbon dioxide has different chemical properties from other atmospheric gases, thus, the carbon dioxide concentration in the air-filled spaces might be affected by interaction with the ice itself or with trapped impurities. The isotopic composition of water, and in particular the concentration of the heavy isotope of oxygen, 18O, relative to 16O, as well as 2H (deuterium) relative to 1H, is indicative of the temperatures of the environment. During cold periods, the concentration of less volatile 2H (18O) in the ice is lower than during warm periods. The reason for this is that at lower temperature, the moisture has