Polar ice cap

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**Earth’s Polar Ice Caps:**
– Earth’s polar ice caps have changed dramatically over the last 12,000 years due to varied solar energy absorption.
– The North Pole is covered by floating pack ice over the Arctic Ocean.
– The Greenland ice sheet covers about 1.71 million km and contains about 2.6 million km of ice.
– Winter Arctic ice extent has decreased about 4.2 percent per decade since 1979.
Antarctica’s ice sheet covers an area of about 14.6 million km and contains between 25 and 30 million km of ice.
– Portions of the Arctic ice that do not melt seasonally can get very thick, up to 3–4 meters thick.
– The area covered by Arctic sea ice ranges between 9 and 12 million km.
– Between 1979 and 2009, the overall average ice coverage declined from 8 million km to 5 million km.
– The Greenland ice sheet contains about 2.6 million km of ice.

**Antarctica and the South Pole:**
Antarctica’s ice sheet covers an area of about 14.6 million km and contains between 25 and 30 million km of ice.
– Around 70% of Earth’s fresh water is contained in Antarctica’s ice sheet.
– The sea ice coverage of Antarctica has a slightly positive trend over the last three decades.
Antarctica’s sea ice extent exceeded 7.72 million square miles in 2014.
– The increase in Antarctic sea ice extent could be due to the reduction in the salinity of the Antarctic Ocean.

**Mars and Polar Ice Caps:**
– Mars has polar ice caps primarily made of water ice with a few percent dust.
– Frozen carbon dioxide makes up a small permanent portion of Mars’ polar ice caps.
– In both hemispheres of Mars, a seasonal carbon dioxide frost deposits in the winter and sublimates during the spring.
– Data collected in 2001 from NASA missions to Mars show that the southern residual ice cap undergoes sublimation inter-annually.
– Fluctuations in Mars’ orbit are causing changes in its ice caps.

**Pluto’s Polar Ice Cap:**
– NASA’s New Horizons mission discovered a polar ice cap on the dwarf planet Pluto in 2015.
– The polar ice cap on Pluto is composed of methane and nitrogen ices.
– The feature on Pluto was confirmed to be an ice cap by the Alice ultraviolet imaging spectrometer.
– The ice cap on Pluto consists of frozen methane and nitrogen.
– New Horizons’ flyby of Pluto in July 2015 provided data confirming the presence of the ice cap.

**Historical Data and Predictions:**
– Since the late 1970s, the Arctic has lost an average of 20,800 square miles of sea ice per year.
– The Antarctic has gained an average of 7,300 square miles of sea ice per year since the late 1970s.
– The Arctic has been losing around 50 cubic kilometers of land ice per year.
– In September 2012, sea ice reached its smallest size ever.
– The rate of warming in the Arctic over the last 20 years is eight times the rate of warming over the last 100 years.

Polar ice cap (Wikipedia)

A polar ice cap or polar cap is a high-latitude region of a planet, dwarf planet, or natural satellite that is covered in ice.

Polar ice cap on Mars, seen by the Hubble Space Telescope

There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land, but only that it must be a body of solid phase matter in the polar region. This causes the term "polar ice cap" to be something of a misnomer, as the term ice cap itself is applied more narrowly to bodies that are over land, and cover less than 50,000 km2: larger bodies are referred to as ice sheets.

The composition of the ice will vary. For example, Earth's polar caps are mainly water ice, whereas Mars's polar ice caps are a mixture of solid carbon dioxide and water ice.

Polar ice caps form because high-latitude regions receive less energy in the form of solar radiation from the Sun than equatorial regions, resulting in lower surface temperatures.

Earth's polar caps have changed dramatically over the last 12,000 years. Seasonal variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the Sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to climate change.

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