The Earth is divided into climate zones based on latitude and solar energy received. The polar zones are the planet’s high-latitude regions, characterized by a lack of warm summers and located around the North and South Poles. The continent located almost entirely within the Southern Polar Zone is Antarctica. Its placement dictates intensely cold temperatures and distinct cycles of light and darkness throughout the year.
Defining Earth’s Polar Zones
The polar zones are defined by geographical lines related to the Earth’s orbit and axial tilt. The planet’s axis is tilted at approximately 23.4 degrees relative to the plane of its orbit, which causes the seasons by changing which hemisphere receives the most direct sunlight. The boundaries of the polar zones are marked by the Arctic Circle in the north and the Antarctic Circle in the south.
These circles are located at approximately 66° 33’ North and 66° 33’ South latitude. Any location poleward of these lines experiences at least one day per year when the sun remains continuously above the horizon and at least one day when the sun remains continuously below the horizon. The Arctic region is primarily an ice-covered ocean surrounded by landmasses, while the Antarctic region is centered on a continent.
Antarctica: The Continent of the South Pole
Antarctica is the fifth-largest continent on Earth, covering over 14 million square kilometers. Nearly 98% of the continent is covered by a massive, permanent ice sheet. This ice sheet is the largest on Earth, holding about 90% of the world’s total ice volume and 70% of its fresh water.
The continental nature of Antarctica is a significant difference from the Arctic, which is mainly an ocean covered by sea ice. The sheer weight of the Antarctic ice sheet has depressed the underlying continental bedrock more than 2.5 kilometers below sea level in certain areas. Averaging about 1.9 kilometers thick, the ice forms a high-altitude polar plateau, making Antarctica the continent with the highest average elevation.
Unique Climatic Features of the Polar Zone
The polar location of Antarctica results in a climate characterized by extreme cold and very low precipitation. The continent holds the record for the lowest measured temperature on Earth, −89.2 °C, recorded at the Vostok Station. Because solar energy arrives at an oblique angle and is spread over a larger area, the polar regions receive the weakest solar radiation.
The large amount of snow and ice also reflects much of the weak sunlight that does arrive, further contributing to the frigid temperatures. This environment is classified as a polar desert because of its minimal annual precipitation, averaging only about 166 millimeters per year. The extreme cold means that nearly all precipitation falls as snow, and weather fronts rarely penetrate far into the continent. The cycle of light and darkness, known as the photoperiod, is also a defining feature. Poleward of the Antarctic Circle, winter brings continuous darkness, while summer features the “midnight sun,” where daylight is continuous for 24 hours.