3 research outputs found
Platelet Ice Under Arctic Pack Ice in Winter
The formation of platelet ice is well known to occur under Antarctic sea ice, where subice platelet layers form from supercooled ice shelf water. In the Arctic, however, platelet ice formation has not been extensively observed, and its formation and morphology currently remain enigmatic. Here, we present the first comprehensive, long‐term in situ observations of a decimeter thick subice platelet layer under free‐drifting pack ice of the Central Arctic in winter. Observations carried out with a remotely operated underwater vehicle (ROV) during the midwinter leg of the MOSAiC drift expedition provide clear evidence of the growth of platelet ice layers from supercooled water present in the ocean mixed layer. This platelet formation takes place under all ice types present during the surveys. Oceanographic data from autonomous observing platforms lead us to the conclusion that platelet ice formation is a widespread but yet overlooked feature of Arctic winter sea ice growth
Overview of the MOSAiC expedition: Snow and sea ice
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