Which geographical area is most notably icy and covers much of Greenland?

The Greenland ice sheet is the most notably icy geographical area that covers much of Greenland. This massive ice sheet is the second-largest body of ice in the world, surpassed only by Antarctica. It plays a critical role in the global climate system, acts as a significant water reservoir, and is a key component of Earth's cryosphere.

The ice sheet can reach depths over 3 kilometers in some areas and contains approximately 7% of the world's fresh water. Due to its size and characteristics, it is a significant focus for climate change studies, as it is melting at an accelerated rate due to global warming, contributing to rising sea levels.

In contrast, the other choices represent different geographical features or locations. The Canadian Shield refers to a large area of exposed Precambrian igneous and metamorphic rocks that covers parts of Canada and the northern United States. Arctic coastlines describe the coastal regions of the Arctic Ocean, which include various landforms but do not represent a single, continuous icy expanse like the Greenland ice sheet. Qaanaaq is a town in northern Greenland, but it represents only a small area and does not encompass the extensive icy regions associated with the predominant ice sheet. Thus, the Greenland ice sheet is the clear and most suitable answer.