As the Arctic continues to rapidly change, one of the most influential changes is the rapid decline of the Arctic sea ice. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition was designed to study this declining sea ice, to explore the responsible processes, and to understand the implications of this change on the ecosystem, circulation patterns, and other global processes. MOSAiC was a year-long, international expedition that drifted with the central Arctic sea ice. This project was one of many coordinated efforts to observe the Arctic atmosphere-sea ice-ocean system from the perspectives of physical, chemical, and biological processes.  The project was specifically designed to quantify the thermodynamic and dynamic drivers of variability in the sea ice. 

During the year-long field expedition, the collaborative research team deployed a collection of observing systems across an array of four primary nodes with spacing of approximately 15 km. Each node included a Seasonal Ice Mass Balance Buoy, an Autonomous Ocean Flux Buoy, and an Atmospheric Surface Flux Station (or equivalent meteorological tower). Additionally, a large network of position buoys was deployed at various scales across the domain. Collectively, these systems made measurements to quantify most of the key components of the sea-ice, upper-ocean, and lower-atmosphere energy and momentum budgets, as well as sea ice movement and deformation on various scales.  The measurement array faced challenges during the year due to the extreme conditions and sea ice dynamics, resulting in some limitations to the distributed measurements, particularly during the second half of the expedition. Nonetheless, the project still assembled some of the most comprehensive observations of this type in the central Arctic, including successful measurements during the rarely observed central Arctic winter. Quality-assured data products have been publicly archived at the Arctic Data Center and have already been broadly utilized by the climate research community.

Scientifically, the project has supported key advances in understanding multi-scale sea ice deformation and its variability seasonally and in relation to atmospheric and oceanic stresses. These observations represented the first time this variability was tracked with high temporal resolution over a full ice growth and melt cycle. The sea ice mass balance was measured for different types of ice, revealing winter ice growth rates of less than one centimeter per day and summer melt rates as large as a few centimeters per day. The snow thermal conductivity was found to be about 0.41 W m^-1 K^-1, which is one third larger than the value assumed in many models. Measurements in the ocean have shown the importance of ice-ocean form drag and large-scale barotropic flow for momentum transfer across the coupled ocean-ice-atmosphere system. Additionally, it was found that vertical ocean heat fluxes across the pycnocline were highly episodic and typically less than one W m^-2. Atmospheric radiative and turbulent heat fluxes were found to frequently oppose each other, intermittently modulated by the presence of leads in the sea ice. The partitioning of atmospheric energy fluxes is constrained by the snow and sea ice thermal conduction, which is dependent on snow-ice physical properties and thicknesses. Near-surface observations were used to successfully derive the annual evolution of surface roughness, supporting improved characterization of, for example, atmospheric momentum transfer to the sea ice. Observation-based, energy budget process relationships have been used to evaluate a suite of operational and research-grade coupled forecast models, revealing significant deficiencies in their representation of clouds, boundary layer processes, and/or snow and ice thermal properties. The data and researchers at part of this collaborative project have already contributed to more than 60 publications, with more to come.

The project’s impact beyond science has been significant. The team has used the excitement of the expedition and the compelling nature of the Arctic to reach broad public and educational audiences. Activities have included curriculum development for audiences from K-12 to college levels, public lectures, and key roles in a MOSAiC documentary film, among others. Through these impacts, the project’s science has been used as a mechanism to raise societal awareness of the changing Arctic system and its global implications.

Last Modified: 11/26/2023
Modified by: Donald K Perovich