X. Ice
Learning Objectives
- Appreciate the roles played by ice in global climate
- Differentiate between glacial ice and sea ice
- Gain proficiency in explaining the steps in the formation of sea ice
- Attain understanding of the difference between pack and fast ice
- Understand the process of iceberg formation
- Grow understanding of the ways that icebergs are classified
- Appreciate importance of understanding complexities of ice failure and its relationship to structural loads
- Differentiate between crushing and flexural loads in terms of mechanism, dynamics, and model equations
- Strengthen ability to explain how global ice cover is responding to climate change
Sections 1, 2, and 4 of this chapter borrow from Introduction to Oceanography by Paul Webb which is licensed under the CC BY 4.0 International License.
Ice covers about 6% of the Earth’s surface, and is responsible for some of the most beautiful and spectacular features in the oceans. Yet what is less appreciated is ice’s influence on global weather and climate. In this chapter we will examine the process of ice formation and the different types of ice that are found in the ocean. For example:
- Ice cover affects the albedo (reflectivity) of the Earth’s surface, influencing the amount of solar radiation that is absorbed.
- Ice insulates the ocean from heat exchange with the atmosphere, preventing large fluctuations in polar water temperatures. One meter of ice cover reduces heat exchange between Earth and the atmosphere by 100 times.
- Seasonal freezing and thawing of ice moderates ocean temperatures through the latent heat of freezing and fusion.
- In all of these ways, ice contributes to the differential heating of Earth’s surface, which serves as the basis for global wind and climate patterns.
In cold regions where structures are exposed to ice-covered waters, such as offshore wind turbines, oil platforms, and coastal defenses, accounting for ice loads is essential to ensure structural safety and durability. Ice-structure interactions are inherently dynamic, influenced by the complex behavior of ice under various environmental forces like wind, water currents, and temperature fluctuations. Designing structures for these conditions involves understanding and anticipating the unique forces exerted by moving ice, which can vary significantly in intensity and impact type.
Engineers face a critical challenge in designing for specific failure mechanisms in order to optimize structural resilience. By favoring bending (flexural) failure over crushing failure, for instance, structures can often absorb or redirect ice forces more effectively, minimizing the risk of severe damage. The choice between these failure modes—crushing and flexural bending—largely depends on factors such as ice thickness, structural geometry, and dynamic load characteristics. Each interaction mode requires a distinct approach for accurate modeling and analysis.
This chapter explores the primary modes of ice-structure interaction: crushing and flexural bending. Each mode presents unique demands on structures and varies based on specific ice properties and environmental conditions. Ice load models combine theoretical understanding with empirical data from laboratory tests and field observations, providing engineers with valuable tools to predict and account for these complex interactions. By delving into these models and the principles underlying ice-induced forces, this chapter aims to equip engineers with the foundational knowledge necessary for designing robust structures that withstand the challenges of ice-covered environments.
The chapter concludes with a discussion of the impacts of climate change on global ice cover.
