Contributions and unrealized potential contributions of cosmogenic-nuclide exposure dating to glacier chronology, 1990-2010

This paper reviews the application of cosmogenic-nuclide exposure dating to glacier chronology. Exposure dating of glacial landforms has made an outsize impact on this field because the technique filled an obvious need that had already been recognized by glacial geologists. By now, hundreds of studies have used cosmogenic-nuclide exposure dating to date glacial deposits, and in fact it is rare to find a study of glacial geology or glacier chronology, or any paleoclimate synthesis that makes use of such studies, that does not involve exposure dating. These developments have resulted in major contributions to glacier chronology and paleoclimate, in particular i) reconstructing Antarctic ice sheet change, ii) establishing the chronology of late Pleistocene and Holocene glacier change in mountain regions where it was previously unknown; iii) establishing the broad chronological outlines of mountain glaciations prior to the Last Glacial Maximum; and iv) gaining insight into subglacial erosional processes through the observation that many glaciated surfaces preserve cosmogenic-nuclide inventories from long past ice-free periods as well as the present one. An important potential future contribution will be the application of the large data set of exposure-dated glacier chronologies to better understand global and regional climate dynamics during Lateglacial and Holocene millennial-scale climate changes. However, this contribution cannot be realized without significant progress in two areas: i) understanding and accounting for geologic processes that cause apparent exposure ages on glacial landforms to differ from the true age of the landform, and ii) minimizing systematic uncertainties in exposure ages that stem from cosmogenic-nuclide production-rate estimates and scaling schemes. At present there exists an enormous data set of exposure ages on glacial deposits, but these data cannot be used to their full potential in paleoclimate syntheses due to an inadequate understanding of geologic scatter and production-rate uncertainties. The intent of this paper is to highlight this situation and suggest some strategies for realizing this potential. (C) 2010 Elsevier Ltd. All rights reserved.