The correct option is Deformation of ice sheets due to mounting pressure.
Explanation
The Ice Cap Climate, designated as EF in the Köppen climate classification system, is primarily found in the interior of Greenland and Antarctica. It is characterized by permanent ice cover where the average temperature of the warmest month never rises above 0°C (freezing point).
Detailed Analysis:
- Deformation of ice sheets due to mounting pressure is Correct: In Ice Cap regions, snow accumulates over millennia. The immense weight of the overlying snow compresses the lower layers, transforming them into ice. Under this mounting pressure, the ice sheets behave plastically and deform, leading to the outward flow of glaciers. This physical deformation is a fundamental characteristic of the ice cap environment.
- Growth of mosses and lichens is Incorrect: The growth of mosses and lichens is characteristic of the Tundra Climate (ET), not the Ice Cap Climate. In EF zones, the surface is permanently covered in ice and snow, preventing any vegetation growth.
- Temperatures rising above freezing point in summer is Incorrect: The primary distinction between Tundra (ET) and Ice Cap (EF) climates is the summer temperature. In Tundra climates, the warmest month averages between 0°C and 10°C. In Ice Cap climates, the temperature remains below freezing even in the warmest month.
- High precipitation throughout the year is Incorrect: Polar regions are often referred to as "cold deserts." The extremely low temperatures mean the air has very little capacity to hold moisture, resulting in very low precipitation levels throughout the year.
Key Takeaway:
The Ice Cap Climate (EF) is defined by permanent freezing temperatures (warmest month < 0°C), a complete absence of vegetation, and the deformation of accumulated ice sheets due to pressure, distinguishing it from the Tundra Climate (ET).