Overview of the MOSAiC expedition: Snow and sea ice
Authors: Nicolaus Marcel , Perovich Donald K. , Spreen Gunnar , Granskog Mats A. , von Albedyll Luisa , Angelopoulos Michael , Anhaus Philipp , Arndt Stefanie , Belter H. Jakob , Bessonov Vladimir , Birnbaum Gerit , Brauchle Jörg , Calmer Radiance , Cardellach Estel , Cheng Bin , Clemens-Sewall David , Dadic Ruzica , Damm Ellen , de Boer Gijs , Demir Oguz , Dethloff Klaus , Divine Dmitry V. , Fong Allison A. , Fons Steven , Frey Markus M. , Fuchs Niels , Gabarró Carolina , Gerland Sebastian , Goessling Helge F. , Gradinger Rolf , Haapala Jari , Haas Christian , Hamilton Jonathan , Hannula Henna-Reetta , Hendricks Stefan , Herber Andreas , Heuzé Céline , Hoppmann Mario , Høyland Knut Vilhelm , Huntemann Marcus , Hutchings Jennifer K. , Hwang Byongjun , Itkin Polona , Jacobi Hans-Werner , Jaggi Matthias , Jutila Arttu , Kaleschke Lars , Katlein Christian , Kolabutin Nikolai , Krampe Daniela , Kristensen Steen Savstrup , Krumpen Thomas , Kurtz Nathan , Lampert Astrid , Lange Benjamin Allen , Lei Ruibo , Light Bonnie , Linhardt Felix , Liston Glen E. , Loose Brice , Macfarlane Amy R. , Mahmud Mallik , Matero Ilkka O. , Maus Sönke , Morgenstern Anne , Naderpour Reza , Nandan Vishnu , Niubom Alexey , Oggier Marc , Oppelt Natascha , Pätzold Falk , Perron Christophe , Petrovsky Tomasz , Pirazzini Roberta , Polashenski Chris , Rabe Benjamin , Raphael Ian A. , Regnery Julia , Rex Markus , Ricker Robert , Riemann-Campe Kathrin , Rinke Annette , Rohde Jan , Salganik Evgenii , Scharien Randall K. , Schiller Martin , Schneebeli Martin , Semmling Maximilian , Shimanchuk Egor , Shupe Matthew D. , Smith Madison M. , Smolyanitsky Vasily , Sokolov Vladimir , Stanton Tim , Stroeve Julienne , Thielke Linda , Timofeeva Anna , Tonboe Rasmus Tage , Tavri Aikaterini , Tsamados Michel , Wagner David N. , Watkins Daniel , Webster Melinda , Wendisch Manfred 
Published: February 2022

Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice–ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice.