The Polar Regions are the areas that surround Earth's geographic North and South Poles. The area surrounding the North Pole is called the Arctic and includes almost the entire Arctic Ocean and northern areas of Europe, Asia, and North America. The area surrounding the South Pole is called the Antarctic and includes the continent of Antarctica and parts of the surrounding Southern Ocean.
Right at the Poles, the Sun shines for half the year and it is dark for the other half of the year. This makes a year like one long day. The Sun rises in spring, reaches its highest point in the sky in summer, and sets in autumn. So the Sun is visible only during the warmer months of the year. When the Sun is visible during summer at the South Pole, it is the dark winter months at the North Pole. The time when the Sun is continuously in the sky is called Polar Day.
At the Arctic and Antarctic Circles there is one full day when the Sun does not set and one day when it does not rise. The Sun does not set on the summer solstice (June 21 in the north and December 21 in the south) and does not rise on the winter solstice (December 21 for the north and June 21 for the south). In the weeks prior to the winter solstice, the number of hours with sunlight become fewer and fewer until on the winter solstice when the Sun does not rise at all for a day. After the winter solstice the amount of daylight increases each day until the summer solstice when the Sun does not set at all for one day.
High in the thermosphere layer of Earth's atmosphere, energized particles that come from the Sun follow Earth's magnetic field lines toward the Poles. The gases of the upper atmosphere light up with the added energy. The display is called the aurora. It can only be seen at high latitudes and is called the Northern Lights in the Northern Hemisphere and the Southern Lights in the Southern Hemisphere.
In the mesosphere of Earth's atmosphere, below the thermosphere and above the stratosphere, noctilucent clouds form in the Polar Regions. This is much higher in the atmosphere than typical clouds, but noctilucent clouds are not typical clouds. The word noctilucent means to glow, and these clouds do glow blue in color when they are lit from below by the setting Sun.
The ozone layer, located in the stratosphere layer of the atmosphere, shields our planet from harmful UV radiation. However, during the 20th Century pollutants destroyed a large amount of ozone. Most of the ozone destruction happened in the part of the stratosphere that is over Earth's Polar Regions. There are now a number of ozone holes, areas where the amount of ozone is only about a third of what it used to be, including a very large hole over Antarctica.
Less solar energy gets to the poles making for lots of cold weather. However, even though both poles get the same amount of sunlight, the North Pole is less cold and has different weather than the South Pole. This is because the North Pole is over the Arctic Ocean, which is less cold than Antarctica and its thick layer of ice. Antarctica is the coldest continent on Earth. It has some of the harshest weather on the planet with high winds and low precipitation. Weather events happen in the troposphere layer of Earth's atmosphere, which is about half as thick at the poles as it is at the equator.
The oceans that are in the Polar Regions are a bit different from other oceans on Earth. There is often sea ice at their surface, especially during the winter months. And those chilly waters are home to some unique marine life.
Seawater from Polar Regions can be denser than seawater from other places. This is because seawater in the polar oceans is cold, and this makes it denser. It can also become saltier than other seawater during the winter when sea ice freezes at the ocean surface removing some of the freshwater to make the ice, which concentrates the salts. The denser seawater sinks to the bottom of the ocean. It travels out of the Polar Regions in slow currents that travel around the bottom of the world's oceans as part of the pattern of global ocean circulation called thermohaline circulation.
Frozen water is found in many different places on Earth. Snow blankets the ground at mid and high latitudes during winter. Sea ice and icebergs float in the chilly waters of polar oceans. Ice shelves fringe lands in Earth's Polar Regions. Glaciers and larger ice sheets move slowly over land in Polar Regions. Glaciers are also found on high mountaintops around the world. The soils of Polar Regions, called permafrost, are filled with frozen water. Together, these different types of frozen water are known as the Earth's cryosphere. Approximately three-quarters of the world's fresh water are frozen in the cryosphere.
Animals that can survive in the Arctic Ocean are adapted for this extreme environment. Some have a special substance within their bodies that prevents their blood from freezing. Others are covered with think layers of fat and fur to keep them warm. Arctic Marine Life
The polar oceans are warming up as Earth's climate changes. Scientists are studying how the polar oceans, the sea ice at their surface, and the marine life within them, are changing in response to recent climate change. They have found that sea ice in the Arctic Ocean is melting so quickly that by the year 2040 there may not be any sea ice in the Arctic during summer months. The melting sea ice threatens Arctic Ocean species such as polar bears. In the Antarctic, scientists are studying the effect of less sea ice on the penguin breeding season.
If it gets warm enough that polar oceans are warmer and sea ice no longer forms, the seawater would not be as dense and would not flow down to the ocean bottom, potentially slowing or stopping global ocean circulation. If the oceans stopped their pattern of global circulation, many aspects of our planet would change including regional climates, the severity of weather events, and marine ecosystems.