Alex Gardner


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Heterogeneous Changes in Western North American Glaciers Linked to Decadal Variability in Zonal Wind Strength
Brian Menounos, Romain Hugonnet, David Shean, Alex Gardner, I. M. Howat, Étienne Berthier, Ben M. Pelto, C. Tennant, J. M. Shea, Myoung-Jong Noh, Fanny Brun, Amaury Dehecq
Geophysical Research Letters, Volume 46, Issue 1

Western North American (WNA) glaciers outside of Alaska cover 14,384 km2 of mountainous terrain. No comprehensive analysis of recent mass change exists for this region. We generated over 15,000 multisensor digital elevation models from spaceborne optical imagery to provide an assessment of mass change for WNA over the period 2000–2018. These glaciers lost 117 ± 42 gigatons (Gt) of mass, which accounts for up to 0.32 ± 0.11 mm of sea level rise over the full period of study. We observe a fourfold increase in mass loss rates between 2000–2009 [−2.9 ± 3.1 Gt yr−1] and 2009–2018 [−12.3 ± 4.6 Gt yr−1], and we attribute this change to a shift in regional meteorological conditions driven by the location and strength of upper level zonal wind. Our results document decadal‐scale climate variability over WNA that will likely modulate glacier mass change in the future.

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Contributions of GRACE to understanding climate change
Byron D Tapley, M. M. Watkins, Frank Flechtner, Christoph Reigber, Srinivas Bettadpur, Matthew Rodell, Ingo Sasgen, J. S. Famiglietti, F. W. Landerer, D. P. Chambers, J. T. Reager, Alex Gardner, Himanshu Save, E. R. Ivins, Sean Swenson, Carmen Böening, Christoph Dahle, D. N. Wiese, Henryk Dobslaw, M. E. Tamisiea, I. Velicogna
Nature Climate Change, Volume 9, Issue 5

Time-resolved satellite gravimetry has revolutionized understanding of mass transport in the Earth system. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has enabled monitoring of the terrestrial water cycle, ice sheet and glacier mass balance, sea level change and ocean bottom pressure variations and understanding responses to changes in the global climate system. Initially a pioneering experiment of geodesy, the time-variable observations have matured into reliable mass transport products, allowing assessment and forecast of a number of important climate trends and improve service applications such as the U.S. Drought Monitor. With the successful launch of the GRACE Follow-On mission, a multi decadal record of mass variability in the Earth system is within reach.