Overview of the MOSAiC expedition: Snow and sea ice

Abstract

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.

Sensitivity of the Arctic Sea Ice Cover to the Summer Surface Scattering Layer

“…A “SSL removal” experiment was completed in July 2020 during the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) expedition in the Central Arctic (Nicolaus et al., 2022) on relatively level ice approximately 1.6 m thick. The experimental setup is shown in Figure 1.…”

Sea ice surface temperatures from helicopter-borne thermal infrared imaging during the MOSAiC expedition

“…Besides the statistical analysis, digital image processing methods could be applied to the image data. Generally, there is a lot of potential for analysis and comparison, in particular, in the context of the broad spectrum of measurements during the MOSAiC expedition 37 – 39 . The variety of measurements taken during the expedition should motivate to compare findings among different variables to gain an improved understanding of connected processes between ocean, ice, air as well as biochemical components of the Arctic.…”

A full year of turbulence measurements from a drift campaign in the Arctic Ocean 2019–2020

“…1 ). Maps of the relative position of sampling sites on the floe, with “Ocean City” being the microstructure sampling site, can be found in the overview publications 25 – 27 . The probe was operated with an electrical winch installed at the edge of the ice hole.…”

“…Except for the two sampling gaps between legs 3/4, and 4/5, profiles were obtained on a near-daily basis. Details on the course of the expedition can be found in overview publications 25 – 27 .…”