The Arctic is the northernmost region of the Earth and it is a polar region characterized by polar conditions climate: cold winters and cool summers. The average winter temperatures can go as low as -40°C and the coldest recorded temperature is -68°C (-90°F). Sea ice, which is formed by frozen seawater, can float on the surface because it has a lower density than seawater. Ice only emerges from the water by about 12% and can become very thick (even meters). Consequences of climate change are very evident here: in the Arctic the air temperature tends to increase faster than the average air temperature of the planet. The extension of the Arctic sea ice, which is measured every year in September, in the period between 1979 and 2016 has decreased almost 43% (an area larger than the whole Australia). Also the thickness of its ice (during the same period of time considered) has reduced considerably, bringing its volume to a reduction of almost 77%. This poses a serious threat to this particular ecosystem.

Surfaces have the ability to reflect a certain proportion of the incident radiation received by the sun. For example, snow reflects more radiation than the same surface covered by a forest. The proportion of reflected radiation is called albedo. This phenomenon is particularly important in the dynamics influencing climate change in particular at these latitudes: Snow and ice reflect a high proportion of the radiation in space (high albedo). If a surface covered by snow or ice melts because of the temperature rise, the surface below, usually darker (such as water or rocks), remains exposed and ends up reflecting much less radiation (low albedo), heating up. As a result, the temperature on Earth continues to rise, causing even more melting snow and ice and further warming. This vicious circle is known as “ice-albedo feedback” (or also “ice-albedo feedback”). The effect of ice-bed feedback plays an important role, especially in the Arctic.

The progressive melting of sea ice in the Arctic summer means that the ocean absorbs much more heat than it would if an ice cover were present. As the ocean heats up, the ice gets smaller and smaller, not only because of solar radiation, but also because warmer seawater further intensifies its melting. The melting of snow and ice increases the warming of the Earth.

A certain fluctuation in Earth’s ice cover is normal however recently the disappearance of ice especially from the poles poses a serious threat because seas levels are increasing threatening the existence of coastal areas. Most of the ice present on Earth is located in the polar and subpolar regions. There are currently two ice caps on Earth: the arctic cap including the Greenland ice, and the antarctic cap. One of the best known effects of climate change is probably the retreat of mountain glaciers and ice caps. Higher temperatures and other locally variable factors, such as annual snowfall, have some impact on glacier retreat. But mountain glaciers and ice caps represent only a small part of the global ice masses. The largest part (i.e., more than 99% of the global land mass of ice) is represented by the Greenland and Antarctic ice caps. Almost all glaciers observed globally lose mass in the long term.

Not only do glaciers retreat, but the amount of snow in the northern hemisphere decreases as well. Since 1966, an average of more than 200 km² do not receive any snow precipitation in respect to the previous year.

Antarctic is covered by the largest ice cap on Earth. Most of Antarctic’s ice is located on the mainland, while another portion floats, as an ice shelf, in front of its shores. There is so much ice in Antarctica that the melting of the entire ice cap would raise the sea level by about 58 meters.

Contrary to what happens in the Arctic, between 1979 and 2016 the surface of sea ice has increased, on an annual average, by about 0.16%. Overall, however, the ice cap is losing mass: while in East Antarctica there is a slight increase in internal ice due to an increase in snowfall, in West Antarctica the ice cap continues to melt, mainly due to the rise in seawater temperature. As a result, the speed at which ice flows from the mainland increases, causing more ice to be transported into the ocean than is formed in the snowfall. Since in many parts of West Antarctica, ice on land infiltrates deeper and deeper below sea level, as the ice recedes, the attack surface for warmer seawater increases. This phenomenon can further accelerate the melting process and consequently the speed of ice flow.
It is estimated that the total annual mass loss of internal ice from 2003 to 2016 is about 141 billion tons.

The Greenland ice cap is the second largest on Earth after the Antarctic ice cap, and it covers almost the entire land surface of Greenland and in some places it is more than three kilometers thick.

Unlike the ice of the Arctic Sea, the Greenland ice cap is not on the sea but it covers the mainland of Greenland. When it melts, the sea level rises. Scientists and climatologists affirm that If the entire mass of the ice cap is to be “lost”, this would cause the sea level to rise by more than seven meters. Between 2002 and 2016, the mass of ice lost of the Greenland ice sheet caused an annual sea level rise of about 0.8 mm, which corresponds to an average annual loss of about 280 billion tons of ice. This phenomenon is mainly caused by increased ice detachment and melting ice on the surface. It must be noted that in recent years the Greenland ice cap has lost mass at an increasing rate and the main cause is global warming.

When ice present on the mainland melts, the water produced by the melting pours into the sea, causing it to rise. If all of this ice melts, it is estimated that the sea level would rise about 66 meters.

The situation is different for sea ice and ice shelves, which are already in the water. If the water and the ice contained in it have the same saline concentration, the melting of this ice produces exactly the same amount of water that was previously displaced by the ice. But in case there is a difference in the saline concentration between sea ice and ice shelves on the one hand, and sea water on the other, the ice moves a little less water than is produced as a result of melting. In the latter case, therefore, the melting of all sea ice and ice shelves would result in a sea level rise of about 4 cm, the most important of which (about 3.6 cm) is attributable to the ice shelves.
The melting of sea ice in the Arctic therefore has a minimal impact on sea level.

Permafrost is the term used to describe a permanently frozen layer on or under earth’s surface, in this case a subsoil in which temperatures of 0°C or below are recorded for at least two years. Permafrost is formed in cold regions, such as Siberia, Canada, Alaska, or in the mountains, and covers about 24% of the surface of the northern hemisphere and it consists of soil, gravel, and sand usually bound together by ice. Permafrost stores the carbon based remains of plants and animals that froze before they decompose.

Due to global warming, permafrost rather than storing carbon could become a significant source of planet heating emissions. In fact If the permafrost melts, those animal and plant remains, which have been stored inside it for thousands of years, are again exposed to microbiological decomposition processes. These processes convert the carbon contained in plants and animals into carbon dioxide (CO₂) and methane (CH4), which can then be released into the atmosphere contributing to the so-called greenhouse effect intensifying global warming.

Higher temperatures also lead to increased plant growth, which in the short term can absorb more CO₂ than is released by thawing. However, unfortunately this does not apply in the long term, where instead we see a new temperature increase on Earth and thus a further melting of the permafrost. This vicious circle is known as “permafrost-carbon feedback”. Through this feedback mechanism, the Earth heats up faster than it would with the impact of human emissions alone.