Sunlight Absorption on the Greenland Ice Sheet Experiment (SAGE) – Tracing black carbon from emissions to deposition

• Main Authors: Polashenski, Chris, Soja, Amber Jeanine, Thomas, Jennie L., Dibb, Jack E., Choi, Hyun-Deok, Flanner, Mark, M, Bergin, Michael H., Casey, Kimberly, Chen, Justin, Courville, Zoe, Lai, Alexandra, Schauer, James J., Shafer, Martin M., Ward, Jamie Lynn
• Other Authors: Dartmouth College Hanover, NASA Langley Research Center Hampton (LaRC), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute for the Study of Earth, Oceans, and Space Durham (EOS), University of New Hampshire (UNH), National Institute of Aerospace Hampton (NIA), Department of Atmospheric, Oceanic, and Space Sciences Ann Arbor (AOSS), University of Michigan Ann Arbor, University of Michigan System-University of Michigan System, Department of Civil and Environmental Engineering Durham (CEE), Duke University Durham, Earth Science System Interdisciplinary Center College Park (ESSIC), College of Computer, Mathematical, and Natural Sciences College Park, University of Maryland College Park, University of Maryland System-University of Maryland System-University of Maryland College Park, University of Maryland System-University of Maryland System, NASA Goddard Space Flight Center (GSFC), Massachusetts Institute of Technology (MIT), ERDC Cold Regions Research and Engineering Laboratory (CRREL), USACE Engineer Research and Development Center (ERDC), University of Wisconsin-Madison, Environmental Chemistry and Technology Program, University of Michigan System
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2016
• Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Greenland; Ice Sheet
• Online Access: https://insu.hal.science/insu-01418732

International audience The SAGE project seeks to understand the impact of light absorbing impurities on the Greenland Ice Sheet (GrIS). In general, the project has found that black carbon and dust concentrations in snow were low in the dry snow zones of the GrIS during 2012-2014 and that their concentrations do not appear to be trending relative to observations of these concentrations in snow over recent decades. We provide a revised analysis of MODIS albedo trends on the GrIS using new collection 6 data. These indicate that observed albedo of dry snow is not substantially trending. Sensor drift which had been present in collection 5 data has been substantially removed and the observed albedo of dry snow on the GrIS is now showing near zero trend.Episodic enhancements in BC deposition are, however, found in specific layers in our extensive snow pit observations. These peak enhancements include concentrations of up to ~40 ng/g BC and would have reduced the albedo of the snow by 0.01-0.02. If timed correctly, the deposition of such a layer could be an important factor in initiating a melt-albedo feedback. Here we present an overview of synthesis work seeking to trace the formation of such a layer back to emission sources and call attention to multiple presentations making up the project. Collectively, the work traces a specific enhanced deposition event occurring on the northwest region of the ice sheet in early August 2013 to source fires in Canada. We summarize the multi-modal approach including remote sensing of aerosols, atmospheric trajectory modeling, chemical transport modeling, and coupled Earth system modeling. The emission, transport, and deposition of the enhanced event is observed and predicted by these tools and we find general agreement between these several modes of sensing and predicting. Further investigations explore other events where BC was emitted and even transported over the ice sheet but did not cause deposition events, resulting in no BC signature in the snow. We also show the spatial ...