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Arctic sea ice has declined dramatically due to climate change. This decline impacts Arctic communities, ecosystems, international trade, and the world's climate. However, due to uncertain physical processes, climate models generally do not capture the severity of the observed decline---adding uncertainty to projections of future climate change. A major uncertainty in the Arctic sea ice component of climate models is how much heat passes through the snow on top of the ice in the winter. This heat flux controls how much ice grows each winter, impacting how much ice survives the summer melt. Snow is an excellent thermal insulator (about ten times more effective than ice), so the snow depth is a critical parameter. Wind redistribution produces highly spatially variable snow depth. Due to logistical and technological challenges, there are few measurements of snow redistribution on Arctic sea ice throughout the winter. We measured snow accumulation and redistribution on drifting Arctic sea ice from October 2019 to May 2020 on the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). In addition to traditional, manual snow depth measurements, we made approximately biweekly observations of the changing snow surface topography at cm-scale vertical accuracy on an area of approximately 0.5 km2 via Terrestrial Laser Scanning. Furthermore, we collected the first measurements of blowing snow loss into open water via cracks in the ice. Our findings suggest that less snow is lost into open water than is assumed by models. However, once the open water has refrozen into young ice, it preferentially accumulates 2.5--8 cm of wind-blown snow, decreasing the rate of ice growth. This preferential accumulation is not represented in climate models, and its omission may cause models to overestimate wintertime heat flux by 3--8% on average in the Arctic. Finally, we observed that snow redistribution from level ice to snow drifts around pressure ridges significantly reduced snow depth on level ice. For level, second-year ice at MOSAiC, this snow redistribution may have increased ice growth by 44--56%. Collectively, our findings deepen our understanding of snow redistribution on Arctic sea ice and will enable better representation of snow processes in climate models.
The following components of this dissertation were published as of the defense. Publication of other components will be completed soon.Clemens-Sewall, D., 2021a. davidclemenssewall/flake_out: FlakeOut 1.0.0. https://doi.org/10.5281/zenodo.5657286 Clemens-Sewall, D., 2021b. Snow thickness measurements on young ice in the Central Arctic during the 2019-2020 Multidisciplinary Drifting Observatory for the Study of Arctic Climate expedition. Arctic Data Center. https://doi.org/10.18739/A2XK84R5C Clemens-Sewall, D., Parno, M., Perovich, D., Polashenski, C., Raphael, I.A., 2022a. FlakeOut: A geometric approach to remove wind-blown snow from terrestrial laser scans. Cold Regions Science and Technology 201, 103611. https://doi.org/10.1016/j.coldregions.2022.103611 Clemens-Sewall, D., Polashenski, C., Raphael, I., 2021. Terrestrial Laser Scanning Data of the ROV (Remote Operated Vehicle) area on the MOSAiC (Multidisciplinary Drifting Observatory for the Study of Arctic Climate) Expedition on February 22, 2020. Arctic Data Center. https://doi.org/10.18739/A2JH3D38M Clemens-Sewall, D., Smith, M.M., Holland, M.M., Polashenski, C., Perovich, D., 2022b. Snow redistribution onto young sea ice: Observations and implications for climate models. Elementa: Science of the Anthropocene 10, 00115. https://doi.org/10.1525/elementa.2021.00115
Clemens-Sewall, David, "Oh the Places Snow Blows: Observations and Impacts of Snow Redistribution on Arctic Sea Ice" (2023). Dartmouth College Ph.D Dissertations. 131.
Available for download on Monday, January 08, 2024