Overview of the MOSAiC expedition: Physical oceanography
Authors: Rabe Benjamin , Heuzé Céline , Regnery Julia , Aksenov Yevgeny , Allerholt Jacob , Athanase Marylou , Bai Youcheng , Basque Chris , Bauch Dorothea , Baumann Till M. , Chen Dake , Cole Sylvia T. , Craw Lisa , Davies Andrew , Damm Ellen , Dethloff Klaus , Divine Dmitry V. , Doglioni Francesca , Ebert Falk , Fang Ying-Chih , Fer Ilker , Fong Allison A. , Gradinger Rolf , Granskog Mats A. , Graupner Rainer , Haas Christian , He Hailun , He Yan , Hoppmann Mario , Janout Markus , Kadko David , Kanzow Torsten , Karam Salar , Kawaguchi Yusuke , Koenig Zoe , Kong Bin , Krishfield Richard A. , Krumpen Thomas , Kuhlmey David , Kuznetsov Ivan , Lan Musheng , Laukert Georgi , Lei Ruibo , Li Tao , Torres-Valdés Sinhué , Lin Lina , Lin Long , Liu Hailong , Liu Na , Loose Brice , Ma Xiaobing , McKay Rosalie , Mallet Maria , Mallett Robbie D. C. , Maslowski Wieslaw , Mertens Christian , Mohrholz Volker , Muilwijk Morven , Nicolaus Marcel , O’Brien Jeffrey K. , Perovich Donald , Ren Jian , Rex Markus , Ribeiro Natalia , Rinke Annette , Schaffer Janin , Schuffenhauer Ingo , Schulz Kirstin , Shupe Matthew D. , Shaw William , Sokolov Vladimir , Sommerfeld Anja , Spreen Gunnar , Stanton Timothy , Stephens Mark , Su Jie , Sukhikh Natalia , Sundfjord Arild , Thomisch Karolin , Tippenhauer Sandra , Toole John M. , Vredenborg Myriel , Walter Maren , Wang Hangzhou , Wang Lei , Wang Yuntao , Wendisch Manfred , Zhao Jinping , Zhou Meng , Zhu Jialiang 
Published: February 2022

Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN’s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present along-drift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean.