Revised estimates of recent mass loss rates for Penny Ice Cap, Baffin Island, based on 2005-2014 elevation changes modified for firn densification

• Published in: Journal of Geophysical Research: Earth Surface
• Main Authors: Schaffer, Nicole, Copland, Luke, Zdanowicz, Christian, Burgess, David, Nilsson, Johan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Uppsala universitet, Luft-, vatten- och landskapslära 2020
• Subjects: Glacier; mass balance; altimetry; Arctic; Canada; Physical Geography; Naturgeografi; Baffin Island; Penny Ice Cap; Airborne Topographic Mapper; Baffin; glacier*; Ice cap; ice core
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-417106; https://doi.org/10.1029/2019JF005440

Repeat airborne or satellite measurements of surface elevation over ice caps are often used tocalculate glacier‐wide surface mass changes over time. However, these measurements typically do notaccount for vertical ice motion caused by firn densification and/or ice flow, so the effect of these factors formass change measurements over an entire ice cap are currently poorly constrained. In this study, we updateNASA Airborne Topographic Mapper (ATM) altimetry elevation changes across Penny Ice Cap (BaffinIsland, Canada) to assess total changes in ice mass from 2005–2014, relative to 1995–2000. Dual‐frequencyGPS measurements and temporal changes in ice core density profiles are used to calculate firn densificationand ice flow to isolate the component of elevation change due to surface mass change. Envisat satelliteimagery is used to delineate the areas impacted by firn densification. These calculations, the first for aCanadian Arctic ice cap, indicate that accounting for firn densification may reduce the inferred surface massloss by ~13–15%. Overall, there has been a fourfold increase in mass loss from Penny Ice Cap between1995–2000 (−1.3 ± 0.7 Gt a−1) and 2005–2013 (−5.4 ± 1.9 Gt a−1). The rapid upglacier migration of theequilibrium line has left large areas of subsurface firn in the current ablation area and has far outpaced theice flow response, illustrating that the ice cap is not in equilibrium and out of balance with the currentclimate.