Final answer:
The Arctic Circle is the latitude in the Northern Hemisphere at 66.5 degrees north where the sun can stay above or below the horizon for a full day during the solstices, defining the 'land of the midnight Sun.' A change in the Earth's tilt would alter the location of the Arctic Circle and the severity of seasons.
Step-by-step explanation:
The Arctic Circle is the southernmost latitude in the Northern Hemisphere at which the sun can remain continuously above or below the horizon for 24 hours; this phenomenon is known as the polar day during the summer solstice and polar night during the winter solstice. At approximately 66.5 degrees north latitude, the Arctic Circle marks the boundary of the 'land of the midnight Sun.' The Earth's tilt of 23.5 degrees to the ecliptic plane determines the position of the Arctic Circle. If this tilt were reduced to 5 degrees, the Arctic Circle would be at 90 degrees minus 5 degrees which equals to 85 degrees north latitude. As a result, the seasonal changes would be milder, and regions within the Arctic Circle would experience less variation in day length and direct sunlight exposure during the year.
If Earth's axial tilt were 16 degrees, the Arctic Circle would be at 74 degrees north latitude, and therefore the difference between it and the Tropic of Cancer, which would be at 16 degrees north latitude, would be 58 degrees. This change in tilt would also lead to milder seasons compared to the current tilt of 23.5 degrees.