Stable isotope development in ground ice along an alpine tundra slope in the Ogilvie Mountains, Yukon Territory

Abstract

Stable isotopic ratios of oxygen and hydrogen (δ18O and δD) from ground ice have been used to reconstruct paleoclimate temperatures spanning the Late Pleistocene and Holocene in subarctic and arctic regions. This is possible due to the strong relations between the isotopic composition of atmospheric moisture and air temperature. Pore and texture ice, common forms of ground ice in permafrost regions, have been used to qualitatively infer the timing of centennial- and millennial-scale climate fluctuations spanning the Holocene and late Pleistocene. However, these records can be difficult to interpret because their source waters may become isotopically altered by local hydrological and phase-change (water-ice) processes before undergoing long-term preservation into the underlying permafrost record. The manifestations and relative contributions of these “secondary” isotopic modifications, which occur within the active layer and underlying transition layer, are poorly understood. In this study, we investigate spatially-varying processes that drive isotopic development in pore and texture ice from a catena within the Southern Ogilvie Mountains, Yukon Territory. The objectives of this study are to (1) establish the history of local permafrost formation using geochemical and traditional cryostructure analyses; (2) examine the stable isotopic relations between the active layer, transition layer, and relict pore and texture ice; (3) assess the impacts of local processes on the stable isotope development of pore and texture ice; and (4) build upon existing evidence for 20th century warming captured by stable isotope records in pore and texture ice.