Why Is Antarctica So Much Colder Than the Arctic?
― Antarctica Is a "High Plateau," the Arctic Is a "Frozen Sea"
The coldest place on Earth lies deep inside Antarctica. The Arctic is cold too, but the South Pole's average yearly temperature is thought to run about 30°C lower than the North Pole's. Both are "the ends of the Earth" — so why such a huge difference? The answer lies in what's underfoot.
Look at a map and the North and South Poles sit facing each other, top and bottom of the globe. Both get low sun, and in winter the sun doesn't rise for months on end. The conditions look nearly identical.
But line up the observational records and the gap is unmistakable. Around the North Pole, winter temperatures are said to stay in the −30s°C. At the South Pole, winter temperatures routinely drop to around −60°C.
At Antarctica's Vostok Station, a reading of −89.2°C was recorded in 1983. Satellite observations have even found values in the high −90s°C on the plateau deep in Antarctica's interior. The Arctic has no record anywhere near that cold.
Just two reasons
The Antarctic continent is covered in ice averaging roughly 2 kilometres thick. The ground at the South Pole sits at about the height of Mt. Fuji's 7th–8th stage. The higher up you go, the colder the air gets.
The centre of the Arctic isn't land — it's ocean. Under a few metres of ice sits seawater that stays liquid at around −2°C without freezing. That ocean keeps sending heat up from below.
In short, Antarctica is "a block of ice high in the sky, with nothing warming it from below." The Arctic is "thin ice at sea level, with a built-in hot-water bottle." Let's look at each in turn.
How much does altitude alone cool things down?
Many people know from experience that it gets cooler as you climb a mountain. When air near the ground rises, the surrounding pressure drops and the air expands. Expanding uses up some of its own heat, so the air cools.
On average, temperature is said to drop about 6.5°C for every kilometre of altitude. The South Pole sits at roughly 2.8 km. Altitude alone works out to about 18°C colder than sea level. Try changing the altitude with the slider in Figure 1.
As shown in the bottom right of Figure 1, altitude accounts for roughly 60% of the gap. The rest of the difference comes down to a second reason.
The Arctic Ocean is a "hot-water bottle under the ice"
Seawater contains salt, so it doesn't freeze until it cools to about −1.8°C. Even when the surface of the Arctic Ocean freezes over, the water beneath stays close to −2°C. So even when the air above is −30°C, just below the ice it's −2°C.
That temperature difference drives heat slowly up through the ice. Because the ice is only a few metres thick, the amount of heat getting through isn't negligible. The left side of Figure 2 shows this.
The ground under the South Pole, as shown on the right of Figure 2, is more than 2 kilometres of ice piled on land. There's no ocean below sending up heat. Heat does leak out from the Earth's interior, but it's tiny, and the thick ice blocks it from reaching the surface anyway.
What's more, in Antarctica, snow and ice barely melt even in summer. The bright white surface reflects most sunlight, so summer warming is much weaker too. In the Arctic summer, cracks open in the sea ice, exposing darker water that absorbs sunlight.
Air that has cooled thoroughly on the Antarctic plateau is heavy, and flows down the gentle slope toward the coast. This is called a "katabatic wind," and near the coast it can blow strongly for days on end. The plateau's cold is, in effect, carried to the sea as wind.
The Antarctic ice sheet is thought to hold about 90% of the ice sitting on land worldwide. If it all melted, sea level would rise by an estimated several tens of metres. Arctic sea ice, by contrast, already floats on the ocean, so its melting barely raises sea level at all.
Summary
Antarctica is about 30°C colder than the Arctic because the South Pole sits atop an ice plateau roughly 2.8 km high. Altitude alone accounts for about 18°C of cooling. On top of that, under the Arctic ice lies an ocean that never freezes and keeps sending up heat — Antarctica has nothing like it.
The Arctic: thin ice floating on the sea.
Antarctica: a thick ice plateau reaching into the sky.
What happens under Antarctica's ice is explored in "Why Is There an Unfrozen Lake Beneath the Coldest Place on Earth?", and the mechanics of air cooling with altitude are covered in "Why Does Wind Suddenly Get Hot After Crossing a Mountain?".
- Set out two cups. Fill one with plain water, and the other with water plus about a tablespoon of salt, stirred until dissolved.
- Put both in the freezer and check every 30 minutes to see which starts freezing first.
- Even once the plain water starts to freeze, the salt water should stay liquid a while longer. That's the same reason the Arctic Ocean doesn't fully freeze even near −2°C.
It's also worth comparing high-mountain temperatures with ground-level ones on the weather forecast — you'll find the rough rule of about 6.5°C per kilometre holds up fairly well.
Want to know more? ― terms, formulas, and textbook connectionsWe mark clearly which level each part belongs to, from middle-school science to university-level coursework
- Middle schoolCovered in middle-school science
- High schoolCovered in high-school Earth Science / Physics
- High school+Advanced high-school content, or textbook sidebar material
- UniversityNot taught in high school — university-level content (meteorology, glaciology)
- ResearchNot yet settled even at university level — an active research question
Middle schoolTerms: this phenomenon has names
- Ice sheet: A continent-spanning mass of ice formed from snow piled up on land and compressed over time. Today found only in Antarctica and Greenland.
- Sea ice: Ice formed by freezing seawater. Almost all the ice covering the central Arctic is this kind.
- Lapse rate: The rate at which temperature drops with altitude. On average, about 6.5°C per kilometre.
Middle schoolHigh schoolCheck with a formula: how much does altitude alone cool the South Pole?
We'll estimate how much of the gap between the North and South Poles' average annual temperatures is explained by altitude alone. We'll also calculate how much heat rises up through Arctic sea ice.
| As symbols | T ＝ T0 − Γ × h |
| In words | Temperature at altitude ＝ sea-level temperature − lapse rate × altitude |
| Where it comes from | When air rises, the surrounding pressure drops and the air expands, using up its own heat to do so (adiabatic expansion). Γ is the average cooling rate, including the effects of water vapour. |
| Heat through sea ice | q ＝ k × ΔT ÷ d (the heat conduction formula: heat flow is proportional to the temperature difference and inversely proportional to thickness) |
| T0 | Temperature at sea level (°C) |
| Γ | Lapse rate (°C/km). Averages about 6.5 |
| h | Altitude (km) |
| q | Heat passing through per square metre per second (W/m²) |
| k | Thermal conductivity of ice (W/(m·K)) |
| ΔT, d | Temperature difference across the ice (°C), and ice thickness (m) |
| North Pole average annual temperature | estimated at about −18°C |
| South Pole average annual temperature | estimated at about −49°C |
| South Pole altitude | about 2.8 km (2835 m) |
| Lapse rate | about 6.5°C/km (international standard atmosphere) |
| Thermal conductivity of ice | about 2.2 W/(m·K) |
| Sea ice thickness (example) | 2 m |
| Top and bottom of winter sea ice | about −30°C and −1.8°C |
| Gap between the two poles' average annual temperatures | 49 − 18 ＝ 31 (°C) |
| Cooling from altitude (Γ × h) | 6.5 × 2.8 ＝ 18.2 (°C) |
| Share of the gap explained by altitude | 18.2 ÷ 31 ≒ 0.59 |
| Remainder not explained by altitude | 31 − 18.2 ＝ 12.8 (°C) |
| Temperature difference across sea ice | 30 − 1.8 ＝ 28.2 (°C) |
| Conductivity × temperature difference | 2.2 × 28.2 ≒ 62 |
| Divide by 2 m thickness (q) | 62 ÷ 2 ＝ 31 (W/m²) |
| Per tatami mat (about 1.6 m²) | 31 × 1.6 ≒ 50 (W) |
Altitude alone explains roughly 60% (about 18°C) of the gap between the two poles. The remaining 13°C or so owes a great deal to the heat the Arctic Ocean keeps sending up from under the ice — about 50 watts per tatami mat's worth of floor. That's like a small light bulb left burning under the floor all winter.
High schoolHigh school+Radiation and "temperature inversions"
High schoolThe ground and snow release invisible infrared radiation, losing heat to space (radiative cooling). Water vapour and clouds in the air catch some of that radiation and send it back down. On Antarctica's high plateau, the air is thin and has very little water vapour, so heat escapes to space more easily.
High school+On the winter Antarctic plateau, the snow surface is the coldest point, with slightly warmer air just above it — a "surface inversion layer." Under these conditions, the usual idea that "higher means colder" doesn't apply right at the surface. The estimate in the main text uses the average cooling behaviour of the atmosphere as a whole, as a rough guide.
UniversityHeat budgets and heat conduction through sea ice
Polar temperatures are governed by the surface heat budget — the balance of net radiation, sensible heat, latent heat, and conductive heat from the ground or ocean. In the Arctic, conductive heat through sea ice, plus large amounts of heat escaping through cracks (leads) in the ice, warm the winter surface. Cooling with altitude is treated using the dry and moist adiabatic lapse rates and standard-atmosphere models. Satellite observations of Antarctica have reported surface minimum temperatures around −98°C in small hollows on the plateau.
📖 For the derivation of the formulas and further reading: "Lapse rate" (Japanese Wikipedia) / Satellite measurements of ultralow surface temperatures in East Antarctica (Scambos et al., 2018)
ResearchWhat's still not fully understood
- How low can surface temperatures actually go? The high −90s°C values found by satellite are thought to appear after several consecutive clear, calm days. Where the theoretical lower limit lies is still being investigated.
- How does thinning Arctic sea ice change winter cold? The thinner the sea ice, the more easily heat passes through from the ocean. This is thought to be one reason Arctic warming is outpacing the global average, though estimates of how much vary by study.
- Why is warming harder to detect in Antarctica's interior? West Antarctica and the Antarctic Peninsula show a clear warming trend, but on the interior plateau the picture is still mixed, and debate continues.
In other words, even this article reflects only "what's understood so far." In particular, treat the "what fraction is due to altitude" figure as a rough guide based on average atmospheric behaviour, not a precise fact.
Textbook connections (by level)
| Level | Subject / unit | Where in this article |
|---|---|---|
| Middle school | Science — weather and its changes (cloud formation) | Why air cools at higher altitude |
| High school | Earth Science Basics — atmospheric structure and heat budget | Lapse rate, radiative cooling |
| High school+ | Earth Science — temperature inversions | Surface inversion layer on the Antarctic plateau |
| University | Meteorology / glaciology (heat budgets, sea ice) | Estimating heat conduction through sea ice |
| Research | Polar climatology | Minimum surface temperatures, pace of Arctic warming |
| ― | Everyday connections | Predicting mountain temperatures, why salt water resists freezing |
- Wikipedia, "Antarctic ice sheet" (南極氷床, Japanese)
- Wikipedia, "Sea ice" (海氷, Japanese)
- Scambos, T. A. et al. (2018) Ultralow Surface Temperatures in East Antarctica From Satellite Thermal Infrared Mapping: The Coldest Places on Earth. Geophysical Research Letters
- Japanese Society of Snow and Ice (日本雪氷学会), ed., New Dictionary of Snow and Ice (新版 雪氷辞典), Kokon Shoin (古今書院)
- Yoshimitsu Ogura (小倉義光), General Meteorology (一般気象学), University of Tokyo Press (東京大学出版会)
※This article is a general-audience science explainer. The figures given are rough estimates meant to aid understanding. Actual temperatures vary by observation site and year.