Ice sheet surface processes
The Greenland Ice Sheet is a large contributor to global sea-level rise primarily due to enhanced melt at the surface of the ice sheet. We investigate key processes that are responsible for surface melt using satellite and drone remote sensing, climate modeling, and fieldwork. In these studies we have provided insight into accumulation rates, cloud radiative effects, and melt-albedo feedbacks. Papers produced in this research area have been cited in recent IPCC reports and have led to refinements in climate models used to forecast ice sheet contributions to global sea-level rise.
Ryan, J. C., Smith, L. C., Cooley, S. W., Pearson, B., Wever, N., Keenan, E., & Lenaerts, J. T. M., (2023), Decreasing surface albedo signifies a growing importance of clouds for Greenland Ice Sheet meltwater production. Nature Communications, 13(1), 1-8, doi:10.1038/s41467-022-31434-w.
Ryan, J. C., Smith, L. C., van As, D., Cooley, S. W., Cooper, M. G., Pitcher, L., and Hubbard, A. L., (2019), Greenland Ice Sheet surface melt amplified by snowline migration and bare ice exposure, Science Advances, 5(3), doi:10.1126/sciadv.aav3738.
Coastal sea ice
Coastal sea ice (also known as landfast or shorefast ice) is an important platform for communities in the Arctic. We combine remote sensing with Indigenous knowledge to understand how transportation and subsistence hunting opportunities have been impacted by diminishing coastal ice in Greenland, Canada, and Alaska. The local knowledge produced by this project provides insight into community resilience and adaptation strategies to a rapidly changing environment.
Cooley, S. W., & Ryan, J. C., (2024), Community-scale changes to landfast ice along the coast of Alaska over 2000-2022. Environmental Research Letters, 19(2), 024013, doi:10.1088/1748-9326/ad1c7b.
- Cooley, S. W., Ryan, J. C., Smith, L. C., Horvat, C., Pearson, B., Dale, B. and Lynch, A. H., (2020), Coldest Canadian Arctic communities face greatest reductions in shorefast sea ice. Nature Climate Change, 1-6, doi:10.1038/s41558-020-0757-5.
ICESat-2
NASA’s ICESat-2 mission, launched in Oct 2018, is a first-of-its-kind satellite laser altimeter that has provided unique insight into ice sheet elevation change. However, it is well-known that light scatters within ice and snow before returning to the satellite. This process, termed subsurface scattering (or volume scattering), has the potential to bias surface elevation measurements from ICESat-2 since light that scatters in the subsurface takes longer to return to sensor (so the surface appear lower than it actually is). In collaboration with scientists at Portland State and University of North Dakota, we are conducting an intensive study of subsurface scattering that includes fieldwork to the Greenland Ice Sheet in 2025 and 2026.
- Allgaier, M., Cooper, M. G., Carlson, A. E., Cooley, S. W., Ryan, J. C., & Smith, B. J., (2022), Direct measurement of optical properties of glacier ice using a photon-counting diffuse LiDAR. Journal of Glaciology, 1-1, doi:10.1017/jog.2022.34.
Drones
We use fixed-wing and multi-rotor drones to investigate snow and ice processes. Drones are useful since since they can collect data with higher resolution than satellite remote sensing and can survey beneath tree canopies and under clouds. We have used fixed-wing drones on the Greenland Ice Sheet to map surface types of the ablation zone and survey marine-terminating glaciers. We have also used multi-rotor drones in the Pacific Northwest to quantify snow depths in burned forests to understand the effects of wildfire on snowpacks.
Ryan, J. C., Hubbard, A. L., Irvine-Fynn, T. D., Doyle, S. H., Cook, J. M., Stibal, M., and Box, J. E., (2017), How robust are in situ observations for validating satellite-derived albedo over the dark zone of the Greenland Ice Sheet?, Geophysical Research Letters, 44, doi:10.1002/2017GL073661.
Ryan, J. C., Hubbard, A. L., Box, J. E., Todd, J., Christoffersen, P., Carr, J. R., Holt, T. O., and Snooke, N., (2015), UAV photogrammetry and structure from motion to assess calving dynamics at Store Glacier, a large outlet draining the Greenland ice sheet, The Cryosphere, 9, 1-11, doi:10.5194/tc-9-1-2015.
