Mapping of Internal Glacial Layers

Abstract

Introduction Internal layers preserved within glacial ice are generally considered to be former deposition surfaces that became entombed in the ice, and therefore the age of a particular layer is equal or isochronous. Internal layers hold a wealth of information about glacier behavior and past climate, and may be detected and tracked with radio-echo sounding (RES) from both the surface and the air (Gogineni et al., 2007; Kanagaratnam et al., 2004). Internal glacial layers have been detected with RES on most polar glaciers, polar ice sheets, and high alpine glaciers, and these layers can often be mapped over great distances. RES detects internal layers, because a small portion of a transmitted electromagnetic radar pulse is reflected back from the layer and is detected by the radar receiver. A radar reflection from an internal layer is caused by a local change in the dielectric constant of the snow or ice, which can be due to an abrupt change in snow or ice density, acidity, or ice crystal fabric orientation (Hempel et al., 2000). If internal layers in glacial ice can be dated