Query: “[Sea ice] also helps regulate the planet’s temperature by influencing the circulation of the atmosphere and ocean.

Relevant passages:
Earth <=SEP=> Earth ( from Eorðe -LSB- Γαῖα , Gaia -RSB- Terra ) , otherwise known as the World or the Globe , is the third planet from the Sun and the only object in the Universe known to harbor life . It is the densest planet in the Solar System and the largest of the four terrestrial planets .   According to radiometric dating and other sources of evidence , Earth formed about 4.54 billion years ago . Earth 's gravity interacts with other objects in space , especially the Sun and the Moon , Earth 's only natural satellite . During one orbit around the Sun , Earth rotates about its axis over 365 times ; thus , an Earth year is about 365.26 days long . Earth 's axis of rotation is tilted , producing seasonal variations on the planet 's surface . The gravitational interaction between the Earth and Moon causes ocean tides , stabilizes the Earth 's orientation on its axis , and gradually slows its rotation .   Earth 's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years . About 71 % of Earth 's surface is covered with water , mostly by its oceans . The remaining 29 % is land consisting of continents and islands that together have many lakes , rivers and other sources of water that contribute to the hydrosphere . The majority of Earth 's polar regions are covered in ice , including the Antarctic ice sheet and the sea ice of the Arctic ice pack . Earth 's interior remains active with a solid iron inner core , a liquid outer core that generates the Earth 's magnetic field , and a convecting mantle that drives plate tectonics .   Within the first billion years of Earth 's history , life appeared in the oceans and began to affect the Earth 's atmosphere and surface , leading to the proliferation of aerobic and anaerobic organisms . Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago . Since then , the combination of Earth 's distance from the Sun , physical properties , and geological history have allowed life to evolve and thrive . In the history of the Earth , biodiversity has gone through long periods of expansion , occasionally punctuated by mass extinction events . Over 99 % of all species that ever lived on Earth are extinct . Estimates of the number of species on Earth today vary widely ; most species have not been described . Over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival . Humans have developed diverse societies and cultures ; politically , the world has about 200 sovereign states .

Climate change (general concept) <=SEP=> Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more. In the time since the industrial revolution the climate has increasingly been affected by human activities that are causing global warming and climate change.The climate system receives nearly all of its energy from the sun. The climate system also radiates energy to outer space. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth\'s energy budget. When the incoming energy is greater than the outgoing energy, earth\'s energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling.\nThe energy moving through Earth\'s climate system finds expression in weather, varying on geographic scales and time. Long-term averages and variability of weather in a region constitute the region\'s climate. Such changes can be the result of "internal variability", when natural processes inherent to the various parts of the climate system alter the distribution of energy. Examples include variability in ocean basins such as the Pacific decadal oscillation and Atlantic multidecadal oscillation. Climate variability can also result from external forcing, when events outside of the climate system\'s components nonetheless produce changes within the system. Examples include changes in solar output and volcanism.\nClimate variability has consequences for sea level changes, plant life, and mass extinctions; it also affects human societies.

Ocean <=SEP=> An ocean ( , the sea of classical antiquity ) is a body of saline water that composes much of a planet 's hydrosphere . On Earth , an ocean is one of the major conventional divisions of the World Ocean , which covers almost 71 % of its surface . These are , in descending order by area , the Pacific , Atlantic , Indian , Southern ( Antarctic ) , and Arctic Oceans . The word sea is often used interchangeably with `` ocean '' in American English but , strictly speaking , a sea is a body of saline water ( generally a division of the world ocean ) partly or fully enclosed by land .   Saline water covers approximately 72 % of the planet 's surface ( ~ 3.6 km2 ) and is customarily divided into several principal oceans and smaller seas , with the ocean covering approximately 71 % of Earth 's surface and 90 % of the Earth 's biosphere . The ocean contains 97 % of Earth 's water , and oceanographers have stated that less than 5 % of the World Ocean has been explored . The total volume is approximately 1.35 billion cubic kilometers ( 320 million cu mi ) with an average depth of nearly 3700 m.   As the world ocean is the principal component of Earth 's hydrosphere , it is integral to all known life , forms part of the carbon cycle , and influences climate and weather patterns . The world ocean is the habitat of 230,000 known species , but because much of it is unexplored , the number of species that exist is much larger , possibly over two million . The origin of Earth 's oceans remains unknown ; oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life .   Extraterrestrial oceans may be composed of water or other elements and compounds . The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan , although there is evidence for the existence of oceans elsewhere in the Solar System . Early in their geologic histories , Mars and Venus are theorized to have had large water oceans . The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water , and a runaway greenhouse effect may have boiled away the global ocean of Venus . Compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice . Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites ; notably , the ocean of Europa is estimated to have over twice the water volume of Earth . The Solar System 's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions . Oceans may also exist on exoplanets and exomoons , including surface oceans of liquid water within a circumstellar habitable zone . Ocean planets are a hypothetical type of planet with a surface completely covered with liquid .

Sea ice <=SEP=> Sea ice arises as seawater freezes . Because ice is less dense than water , it floats on the ocean 's surface ( as does fresh water ice , which has an even lower density ) . Sea ice covers about 7 % of the Earth 's surface and about 12 % of the world 's oceans . Much of the world 's sea ice is enclosed within the polar ice packs in the Earth 's polar regions : the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean . Polar packs undergo a significant yearly cycling in surface extent , a natural process upon which depends the Arctic ecology , including the ocean 's ecosystems . Due to the action of winds , currents and temperature fluctuations , sea ice is very dynamic , leading to a wide variety of ice types and features . Sea ice may be contrasted with icebergs , which are chunks of ice shelves or glaciers that calve into the ocean . Depending on location , sea ice expanses may also incorporate icebergs .