Final answer:
Maritime polar air masses are cool and moist, forming over high-latitude oceans and moderated by ocean currents like the Gulf Stream, resulting in temperate climates in regions that might otherwise experience cold conditions.
Step-by-step explanation:
The characteristic of maritime polar air masses can be best described by recognizing that they are moist and cool. These air masses form over high-latitude oceans, such as near Norway's coast within the Arctic region. Despite proximity to the poles, maritime polar regions benefit from milder conditions compared to continental polar regions due to water's ability to stabilize temperatures. For example, the Gulf Stream significantly moderates climates in Western Europe by transporting warm tropical waters northward, allowing for a temperate type C climate, contrasted with the colder type D climates of Eastern Europe. Air masses have profound effects on the global pattern of precipitation, with dry belts at approximately 30° N and S latitudes and more productive zones where cold and warm oceanic waters mix, like the Subtropical Convergence in the Southern Ocean.