How Sea Ice Works
In September 2026 Antarctic sea ice peaked at its third-lowest winter maximum in the satellite record, while Arctic ice reached a minimum tied for tenth-lowest. This film explains how sea ice works: why salt water freezes at minus 1.8 degrees, how slush becomes pancakes and then floes metres thick, how freezing squeezes out salt and helps feed deep ocean circulation, why the two poles behave so differently, how a white surface reflects sunlight and a dark one absorbs it, how satellites measure the ice through clouds, and why melting sea ice does not raise sea level. Freeze the sea, watch brine sink, switch between the poles, and melt the mirror.
The frozen mirror
An ocean that freezes and thaws every year.
Colder than zero
Salt water needs extra cold to freeze.
Pancakes on the sea
From needles of ice to a solid lid.
Salt that sinks
Freezing at the surface stirs the deep ocean.
Mostly below the surface
Floes collide and pile up.
Mirror-image poles
Geography decides how the ice behaves.
A white shield
How much sunlight bounces straight back.
Melting feeds melting
A loop that amplifies warming at the poles.
Microwave eyes
A record that began in 1978.
A shrinking summer
The twenty lowest years are the last twenty.
A sudden turn
Decades of slow growth, then sharp losses.
The ice in your glass
Floating ice is already displacing its weight.
An open Arctic
What the climate assessment projects.
Breathing ice
Growing and shrinking with the seasons.
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