One pole is an ocean, the other is a continent
This is the difference that explains almost everything else. The ARCTIC is a sea with land around the edges: reach the NORTH POLE and you are standing on floating ice a few metres thick, with four kilometres of water underneath. Antarctica is the reverse — a continent buried under ice up to four kilometres deep, with sea around it.
So the south is far colder, because thick ice on high ground holds cold better than a thin skin over a comparatively warm ocean. It is also why the Arctic has land mammals and Antarctica essentially does not, and why the sea ice is a hunting platform rather than a place — the polar animals that use it are walking on frozen ocean.
Melting sea ice does not raise the sea
Put an ice cube in a full glass of water and let it melt. The glass does not overflow. Floating ice already pushes aside exactly its own weight in water, so when it turns back to liquid it fills precisely the space it was displacing — and the same is true of every FLOE and ice CAP drifting on the Arctic Ocean.
What does raise the sea is ice sitting on land: the Greenland sheet, and every GLACIER sliding down a valley. That water is not in the ocean yet. The distinction is one to hold on to, because the loss of Arctic sea ice matters enormously for other reasons — WHITE ice reflects sunlight, dark water absorbs it, so melting speeds up its own melting — just not for that one.
An igloo works because snow is mostly air
Fresh SNOW is around ninety per cent trapped air, which makes it a surprisingly good insulator — closer to a woolly jumper than to the solid ice it becomes when crushed. Build a dome out of it and body heat alone can hold the inside forty degrees warmer than the BLIZZARD outside.
The design does the rest. The entrance tunnel sits below the living floor so the COLD air, being heavier, pools there and cannot climb in. The sleeping platform is built high, because the warm air rises to meet it. And the dome shape means every block leans on its neighbours, so a well-made one will hold the weight of a standing adult on the roof.
The lights are the sun arriving late
The AURORA is not weather. It is particles thrown off the sun, caught by Earth's magnetic field and funnelled down towards the POLAR regions, where they slam into the atmosphere and make the gas glow. That funnelling is what shapes the display into a ring around the magnetic pole rather than letting it appear wherever it fancies.
The colours tell you what was hit and how high up. Oxygen high in the atmosphere glows red, oxygen lower down the familiar green, nitrogen blue and purple below that. The rest of the grid is the ordinary business of being that far north: FROST and an ICICLE, the CHILL of the WIND, driving SLEET, a FROZEN TUNDRA too cold for trees, and an ICEBERG that FREEZE-s from snowfall on land and shows a tenth of itself above water.