Climate in Antarctica

In Antarctica there is a polar climate, with temperatures below freezing all year round in the large part of the territory, and for most of the year along the coasts.
According to the Köppen classification, in the first case we speak of a glacial climate (abbreviation: ET), in the second, in which the temperature slightly exceeds freezing in summer, of a tundra climate (abbreviation: EF).
In winter, from May to September (April to September at the South Pole), the lowest values in the world are reached in inland areas.
In much of the territory, summer is short and corresponds to the two months of December and January.
Instead, in the northernmost part of the Antarctic Peninsula, north of the Polar Circle, and in the surrounding islands, summer is a longer season, in fact it goes from December to February or even March.

Index

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• Ice cap and mountains
• Temperatures - South Pole, Vostok, Casey, Esperanza
• Winds
• Precipitation
• Sun, thermal inversion and optical phenomena
• Variations and trends
• When to go
• What to pack

Ice cap and mountains

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Antarctica is the coldest continent on Earth.
Larger than Europe, and roughly circular-shaped, this continent is nearly centerd on the South Pole and is surrounded by the three oceans of the Southern Hemisphere, namely, Atlantic, Pacific and Indian.
The situation is quite the opposite in the Arctic region, where there is a frozen ocean (the Arctic Ocean) surrounded by continents.



The South Pole is colder than the North Pole precisely because of this different geographical configuration, to which must be added the influence of the altitude: owing to the huge ice sheet that covers the continent (about 90% of the ice, which corresponds to about 70% of freshwater on our Planet, is found in Antarctica), the average altitude is around 2,000/2,400 meters (6,600/8,000 feet), with large areas above 3,000 meters (9,800 feet), so it is far higher than in the other continents, where it's around 700/800 meters (2,300/2,600 feet).
Because of these factors, at least in the lowest layers of the atmosphere, there is a circulation that prevents the penetration of mild ocean winds towards the interior: both air and sea currents flow around the continent with an almost circular motion, from west to east (the so-called Antarctic Circumpolar Current).
Below the ice cap, there are plains and even depressions, also caused by the enormous weight of the ice itself. However, there are mountains as well, whose highest point is Mount Vinson, 4,892 meters (16,050 feet) high, not far from the Weddell Sea.
There are also two large and partially (but permanently) frozen seas, the Ross Sea and the Weddell Sea, formed by two bays that penetrate the continent.
The total size of the ice sheet (the one that covers the mainland plus the marine one) vary from about 14 million square kilometers (5.4 million square miles) in March to about 22 million km² (8.5 million mi²) in September: in autumn, the ice advances by about 4 km (2.5 mi) a day, and at the end of winter, almost the entire continent is surrounded by sea ice. The largest iceberg that calved from the ice, was 40 km (25 mi) wide and 400 km (250 mi) long, so it was larger than Belgium.

Temperatures

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The average temperatures of the continent are extremely low. However, there are notable differences between the various areas, due to continentality, i.e. the distance from the sea, but also to the altitude.
In the coldest months, July and August, the daily average is -5/-6 °C (21/23 °F) in the South Shetland Islands, -10/-12 °C (10/14 °F) in the Antarctic Peninsula, -15/-18 °C (0/5 °F) on the coast surrounding Antarctica, while it drops below -60 °C (-76 °F) in the coldest areas of the plateau.
In the warmest months, December and January, the daily average is 1/2 °C (34/35.5 °F) in the South Shetland Islands and the Antarctic Peninsula, it ranges from -2 to +2 °C (28.5 to 35.5 °F) along the coast surrounding Antarctica, while it drops below -30 °C (-22 °F) in the coldest areas of the plateau.

At the South Pole, 2,800 meters (9,200 feet) above sea level, the average annual temperature is -48.65 °C (-55.5 °F), ranging from about -26.5 °C (-15.5 °F) in December to about -60 °C (-76 °F) in July. The lowest recorded temperature is -83 °C (-117 °F), while the highest is -12 °C (10 °F).
Here are the average temperatures.

However, the lowest temperature ever recorded in the continent, which is also the world record, belongs to the Russian station of Vostok, which is located at an even higher altitude, 3,500 meters (11,500 feet) above sea level, and further from the sea, and where the temperature reached as low as -89.2 °C (-128.6 °F) in in 1983. Here, the highest temperature ever measured is -14 °C (7 °F). The average annual temperature is -54.5 °C (-66 °F).

However, the coldest area of Antarctica, and therefore of the Earth, is larger, and includes the geometric center of the continent, where the former Soviet "Pole of inaccessibility" station is located, at 3,800 meters (12,467 ft), and where an average annual temperature of -58.2 °C (-72.8 °F) was measured. Not far away, in the 1960s, an annual average of -56.7 °C (-16 °F) was recorded in the American Plateau Station, at 3,624 meters (11,890 ft).
In colder areas, more ice has accumulated over the millennia, in the form of domes, as if they were vast mountains smoothed by the wind.
Further east of Vostok, the site known as Dome C, where the Franco-Italian Concordia station is located, at 3,230 meters (10,600 ft) above sea level, is also very cold.
However, from satellite observations, it seems that the coldest area is between the sites called Dome A and Dome F. At Dome A, located at 4,000 meters (13,000 feet) above sea level, a temperature of -93 °C (-135 °F) has been estimated.

In coastal regions, the climate is much milder. This happens because of the lower latitude (in some areas, the coasts are beyond the polar circle) and of the lower altitude (unlike in the interior, where there is a thick ice cap, here we are obviously at sea level), as well as of the influence of the sea. Here, the temperatures rarely drop below -30 °C (-22 °F) even in winter, while they can exceed the freezing point in summer.
The highest recorded temperatures ever measured on the continent is 18.3 °C (64.9 °F), recorded at the Argentine base of Esperanza (see below) in February 2020. There is then an unusually mild area, located closer to the South Pole, the McMurdo Dry Valleys, at a latitude of 77 degrees South, near McMurdo station. In this area, in the former Vanda station, located near a salt lake, on 5 January 1974, a temperature of 14.5 °C (58 °F) was recorded.
Outside the continent, on the island of Signy, belonging to the South Orkney archipelago, at 60 degrees south latitude, a temperature of 19.8 °C (67.6 °F) was recorded in January 1982.

At the Australian Casey Station, located on the coast of the Indian Ocean, at a latitude of 66 degrees south, the average temperature ranges from -15 °C (5 °F) in June to around 0 °C (32 °F) in January.

At Esperanza Base, located in the northernmost and mildest part of Antarctica, at the tip of the Antarctic Peninsula, at a latitude of 63 ° south, the temperature is even higher, in fact, the daily average ranges from a low of -10.2 °C (13.7 °F) in June to a high of 1.5 °C (35 °F) in January. The cold record is -32 °C (-25.5 °F).



Here are the average annual temperatures on the continent.

Winds

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Along with the record of low temperatures, Antarctica also holds the record of the strongest winds: winds between 100 and 200 kilometers (60 and 125 miles) per hour are not uncommon, but sometimes they even exceed 300 kph (185 mph), with maximum gusts of about 360 kph (220 mph).
The blizzard is so terrible that it is an obstacle to human activities even larger than the cold itself. It usually blows from inland to the sea, it is more intense in winter than in summer, and it is due to the huge difference in temperature (and hence in air pressure) that is generated between inland and coastal areas.
These strong winds cause a huge wind chill (the phenomenon whereby the wind makes it feel colder than the real temperature), so much so that the perceived temperature in the worst moments can be far lower than -100 °C (-150 °F).
The winds that blow from the higher elevations of the interior, and descend in altitude, finally reaching the coasts, are called katabatic. General atmospheric circulation plays a role in the formation of these winds: at high altitudes, subtropical winds blow towards the interior, in order to prevent the continent from getting even colder; then, these air masses descend downwards (subsidence), and after having cooled down above the ice cap, they move towards the exterior of the continent.
In the Dumont d'Urville station, for example, there are on average 11.6 days per month when the wind exceeds 100 kph (60 mph), with a minimum in January (of 7 days) and a maximum in August and September (of 14 days).
This station has experienced at least one episode with wind gusts above 230 kph (145 mph) in all months of the year, and the overall record, which has occurred in June, is an astonishing 324 kph (201 mph).
These cold winds, once they reach the sea, feed low pressure systems which give life to the so-called West Wind Drift, which sweeps the oceans around Antarctica: the result is a stream of water that travels from west to east at a speed of 20 Km (12 mi) per day.
On the central plateau of Antarctica, on the other hand, the wind, although it blows often, is less intense. At the South Pole, the average wind speed is 20 kph (12.5 mph), and so far, record gusts have never reached 100 kph (62 mph).

Precipitation

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Winds shape the surface of ice and snow, in a manner that reminds of sand dunes in the desert. Actually, precipitation in much of Antarctica is desert-like almost everywhere: in the interior, it's lower than 50 millimeters (2 inches) per year, and it exceeds 300 mm (12 in) only near the coasts, with a maximum of 700 mm (27.5 in) in the Antarctic Peninsula. Strange as it may seem, drought makes fires dangerous because of the limited availability of liquid water.



Looking at the last two maps, we can see that there is a correspondence between temperature and precipitation. An average temperature of -25 °C (-13 °F) roughly corresponds to an average precipitation of 400 mm (16 in), while temperatures below -55 °C (-67 °F) correspond to precipitation below 50 mm (2 in). This is explained by the fact that at -55 °C (-67 °F), the saturated vapor pressure is 30 times lower than at -25 °C (-13 °F): in other words, the air can hold much less moisture, so it's not able to produce a high amount of precipitation.
And so the coldest areas are arid, officially among the most arid in the world: precipitation in the South Pole amounts to just 2.3 mm (0.1 inch) per year, and at Vostok, it amounts to about 20 mm (0.9 in) per year, although the real quantity is higher because the snow, which is very frequent but falls mostly in the form of light sleet, is carried away by the wind, which finds no obstacles in this flat desert, except the buildings of the scientific research stations.
On the coasts, in addition to having heavier snowfalls in the long winter months, there can also be some rain in summer, when the temperature rises above freezing.

Sunshine, temperature inversion and optical phenomena

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The amount of sunshine is not very abundant in peripheral and coastal areas: in autumn and winter, the days are very short, while in spring and summer, the sun is often covered with clouds. For example, Casey Station receives just 1,150 hours of sunshine per year. Here are the average sunshine hours per day.

In the South Shetland Islands, north of the Antarctic Peninsula, there is a very low amount of sunshine, from 500 to 600 hours per year, also due to frequent fog. Further north, in the South Orkneys, the hours of sunshine drop to just over 400 per year: we are in the least sunny area of the Planet.

On the contrary, in the central part of the continent, such as the South Pole and Vostok, while it is true that the sun never rises in the long polar night, in the summer months, not only the sun is always above the horizon, but also the sky is almost always clear. So, the Vostok station, as well as the coldest, is also one of the sunniest places on the planet, with 3,760 hours of sunshine per year, despite the fact that, as we said, the sun always remains below the horizon in the winter months.

However, snow and ice reflect most of the solar radiation that reaches the ground, while in winter, the absence of sunlight causes a radiation deficit, which tends to cool down the soil.
This produces a unique temperature inversion, which, in winter, can exceed 30 degrees Celsius (55 degrees Fahrenheit) between the ground and an altitude of 1,000 meters (3,300 feet) above, also because of the warmer subtropical currents, which flow, as mentioned, at high altitudes. In July 1989, at Vostok, a difference of 34 °C (61 °F) was recorded between the ground, where the temperature was -78 °C (-108 °F) and 600 meters (2,000 feet) above, where it was -44 °C (-47 °F); the temperature was -73 °C (-99 °F) still at 8,000 meters (2,600 feet), so it was higher than at ground level.
Along with electromagnetic factors, temperature inversion causes curious optical phenomena, such as sundogs and halos around the sun or moon.
Owing to both low temperatures and strong winds, the air in Antarctica is characterized by exceptional transparency, brightness and acoustics: it is possible to spot mountains at a distance of as far as 550 km (340 mi).
The absence of objects such as trees and houses, however, makes it very difficult to evaluate the distances. Effects such as light refraction and reflection also cause frequent mirages, favored by the presence of tiny ice crystals that are continuously formed in the air because of low temperatures.



Meteorological observations in Antarctica started very late, partly because of the adverse environmental conditions. Prior to 1957-58, the International Geophysical Year, there were stations only in the Antarctic Peninsula and the Ross Sea.
But it did not take long for scientists to understand the importance of knowing the climate of the continent, in addition to the fact that it offers a privileged point of observation for the study of the past and present climate of the Earth (in fact, ice layers preserve the memory of the chemical composition of the atmosphere of past ages, from which we can deduce the air temperature), but also for the climate prediction of the future.
Phenomena such as global warming and the ozone hole, which was discovered here and here has its greatest intensity, have attracted and still attract groups of scientists who continually defy the cold and the wind to carry out their studies.

Changes and trends

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In Antarctica, temperature variations from year to year are considerable: the standard deviation of the mean annual temperature is generally around 0.61/1.56 °C (1/2.8 °F), while for example it's 0.5 °C (0.9 °F) in London.
The difference in the average temperature from one year to another can be as high as 4 °C (7 °F).
As for the trend, the South Pole does not show a clear temperature rise over time, while coastal areas show a remarkable rise of almost 0.3 °C (0.5 °F) every 10 years in the last 4 decades, with peaks of 0.5 °C (0.9 °F), i.e. more than three times the world average.
On the contrary, until not many years ago, there seemed not to be any increasing trend in temperature in the Arctic.
Contrary to what happens in the rest of the world, where glaciers are retreating both in the mountains and in the Arctic region (see Greenland and Arctic Ocean), ice extent in Antarctica has actually increased (though less than it has declined in the rest of the world).
Contrary to what one might think, even this phenomenon may be due to global warming: on the one hand, in cold regions, an increase in temperature allows for an increase in snowfall (as long as the temperature remains below freezing); on the other hand, the greater ice extent may be due to the higher speed at which the ice from the inner part of the continent slides towards the sea. However, by 2017, the Antarctic ice has also fallen to historic lows.

When to go

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The best time to visit Antarctica is summer, in December and January in inland areas, and from December to February in the Antarctic Peninsula and the northernmost islands (Southern Shetland, Southern Orkney), since it is the mildest (or rather, least cold) period of the year, and when the days are long. Along the northernmost coasts, in the Antarctic Peninsula, temperatures are around freezing or slightly below at night and above freezing during the day, while they are below freezing, even by several degrees, in the interior of the continent. In any case, snow on the ground can be be found even on the coasts, or nearby.
The peak of tourists is recorded between Christmas and New Year's, and prices are also higher during this period.
In general, however, cruises are organized from November to March. At the beginning of the period, in November and even more likely in October, it is often necessary to use icebreakers.



In summer, the days are very long everywhere. At Esperanza Base, at 63 degrees south latitude, therefore in the northernmost area, the sun always goes below the horizon at night, however, there are the white nights, in which it doesn't get completely dark even at midnight, from November 2nd to February 9th. The longest day is December 21, the southern hemisphere's summer solstice.
At the South Pole, on the other hand, there are six months of darkness and six months of light. The sun never sets between the spring equinox and the autumn equinox, i.e. from September 22nd to March 21st. In addition, summer at the South Pole is very sunny, and from November to January the sky is almost always clear.
Sea ice extent is at its lowest in February, when nearly all sea ice melts, and at its highest in September, when large portions of the sea around Antarctica, including the Weddell Sea and the Ross Sea, are frozen.
February and March are the best months for whale watching.
The closest cities from which expeditions to Antarctica depart are Punta Arenas, Chile, and Ushuaia, Argentina. However, there are also cruises that depart from Hobart in Australia or Invercargill in New Zealand.

What to pack

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Even if you travel in the summer, and even if you visit the Antarctic peninsula, which is located south of Argentina and Chile and is the mildest area, you need to be equipped against the cold. It is better to dress in layers, usually three, comfortable but warm, both for the low temperatures and for the wind, which you will experience if only on cruises and boat transfers, perhaps to spot whales. The innermost layer should be thermal, while the outermost one should be waterproof (even if it doesn't rain or snow, during expeditions in "zodiac" inflatables you get splashes and spray from the sea).
It is also necessary to bring ski gloves, a woolen hat (close-fitting so that it does not blow away with the wind, and which also covers the ears) and a neck gaiter (preferable to the scarf since it doesn't fly off). For safety, you can bring spare gloves and beanie, in case the former get lost.
When it's sunny, since, if outdoors, you are always either by the sea or in snowy areas, you need to wear sunglasses that protect against ultraviolet rays, and sunscreen is very useful as well, along with lip balm.
Bring at least two pairs of socks, one of which warmer and to be worn outdoors only.
Knee-high rubber mud boots are preferable to hiking boots, but are usually provided by the company organizing the expedition.
In general, the companies that organize the expedition have medicines available for nausea and seasickness, but it can be useful to bring your own, since you will probably need them sooner or later, especially in the Drake Strait, where the sea is often rough.

It may also be useful to bring:
Lightweight binoculars.
The water canteen is preferable to bottles of water. In general it is good to avoid disposable products, however, it is advisable to bring plastic bags to put the waste, which you will have to carry in your backpack.
Cold resistant camera with neck strap. Spare batteries and SD memory cards.
Book, e-book or podcast for long journeys (even by plane or at the airport). Pen and notebook.
Electrical adapter / converter.

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See also the temperatures month by month