Quantifying Growth of Pancake Sea Ice Floes Using Images From Drifting Buoys. Issue 4 (25th April 2018)

• Record Type: Journal Article
• Authors: Roach, Lettie A.; Smith, Madison M.; Dean, Samuel M.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 4(2018)
• Page Start: 2851
• Page End: 2866
• Publication Date: 2018-04-25
• Subjects: sea ice -- ocean waves -- wave‐ice interactions -- sea ice floe size -- image processing -- in situ observations; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2017JC013693
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: New sea ice in the polar regions often begins as small pancake floes in autumn and winter that grow laterally and weld together into larger floes. However, conditions in polar oceans during freezeup are harsh, rendering in situ observations of small‐scale sea ice growth processes difficult and infrequent. Here we apply image processing techniques to images obtained by drifting wave buoys (SWIFTs) deployed in the autumn Arctic Ocean to quantify these processes in situ for the first time. Small pancake ice floes were observed to form and grow gradually in freezing, low‐wave conditions. We find that pancake floe diameters are limited by the wave field, such that floe diameter is proportional to wavelength and amplitude over time. Floe welding correlates well with sea ice concentration, and the observations can be used to estimate a key model parameter for floe size evolution. There is some agreement between observed lateral growth rates and those predicted using a theoretical model based on heat flux balance, but the model lateral growth rates are too conservative in these conditions. These results will be used to inform description of lateral floe growth and floe welding in new models that evolve sea ice floe size distribution. Plain Language Summary: Sea ice, which is frozen seawater, can take many different forms depending on its surrounding conditions. If the ocean is still, it might form as large, thin sheets of sea ice. If there are waves on the ocean surface, sea ice forms as "pancake" floes—small circular pieces of ice. There are very few close‐up observations of sea ice made during freezing conditions, and even less where waves are present such that pancake floes form. This is partly due to the challenge of completing a field campaign in the cold and dark of winter, as well as the limited number of platforms capable of making observations in thin, new ice. Here we present an analysis of images captured by buoys that drift with the ice in the Arctic during freezeup. These images show how pancake floes evolve over time as a result of wave and freezing conditions. We compare observations to what different theoretical models would predict for the observed conditions. These comparisons can be used to inform the development of new large‐scale models for sea ice evolution, which is important for polar climate. Key Points: Images from drifting buoys provide the first in situ quantification of sea ice floe growth processes Lateral floe growth is limited by stress induced by the wave field Observed floe behavior agrees with theoretical models and informs model parameter choices