Model Predictions of Wave Overwash Extent Into the Marginal Ice Zone

• Published in: Journal of geophysical research. Oceans Vol. 127; no. 10
• Main Authors: Pitt, Jordan P. A., Bennetts, Luke G., Meylan, Michael H., Massom, Robert A., Toffoli, Alessandro
• Format: Journal Article
• Language: English
• Published: 01.10.2022
• Subjects: marginal ice zone; overwash; sea ice; waves
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2022JC018707

In the marginal ice zone (MIZ), where ocean waves and sea ice interact, waves can produce flows of water across ice floe surfaces in a process known as wave overwash. Overwash potentially influences wave propagation characteristics, floe thermodynamics, and floe surface biological and chemical processes. However, the extent of the MIZ affected by overwash and its dependence on prevailing wave and ice conditions is unknown. In this paper, we propose a model of overwash extent caused by irregular incoming waves into a MIZ consisting of a random floe field. We validate the overwash extent model against laboratory experiments. We use the model to study mild to extreme incoming waves to floe field characteristics of the spring–summer ice retreat and autumn–winter ice advance and with compact ice edges. Overwash is typically predicted to extend a few kilometers and is generally greater for the autumn–winter advance than the spring–summer retreat. The model predictions provide a basis for improved understanding of the impacts of ocean waves on the ice cover. We also apply the model to incoming waves and a floe field with a diffuse ice edge representative of conditions during a field experiment, predicting overwash extents up to 16 km. During the field experiment, the wave and ice floe properties were intermittently monitored by a camera system, demonstrating how the sparse field data available on overwash can be advanced. Plain Language Summary Wave overwash is the flow of water across the surface of a thin floating body due to passing waves. It is an important process in the marginal ice zone (MIZ) where sea ice floes and ocean waves interact. Overwash reduces the energy of ocean waves, removes snow from, and wets the sea ice surface, which can drive growth or melting. Water left on the sea ice surface can host organisms and affects chemical processes taking place there. Overwash is pervasive in laboratory experiments where it has been measured and studied. In contrast, there are few reports of overwash in the field and the extent of its occurrence has not been measured. We propose a model to predict the region of the MIZ in which overwash occurs. We use the model to compare overwash extents for MIZs associated with the spring–summer ice retreat and autumn–winter ice advance for calm to energetic wave conditions, including the conditions observed during a winter Antarctic icebreaker voyage. For field conditions, the model predicts that overwash typically extends at least several kilometers into the MIZ, indicating that it likely contributes to the ice edge evolution. Key Points A mathematical model is proposed for the extent of wave overwash of ice floes in the marginal ice zone (MIZ) based on coupled floe–wave motions Frequent overwash is predicted up to 16 km from the ice edge during a voyage into Antarctic MIZ composed of pancake ice Wave overwash is predicted to be a persistent feature of the outermost MIZ, likely contributing to the evolution of the ice edge