The 'ice finger of death': why ice grows down under Antarctica

Under Antarctic sea ice, a white column of ice grows to the seabed and freezes starfish and urchins. The 'ice finger of death' is a tube of ice formed by very salty, very cold brine that leaks from freezing sea ice, sinks and freezes the seawater around it.

• Freezing seawater pushes salt into brine channels (120–156 psu at −12 °C, White Sea 2014)
• The sinking brine freezes the seawater it touches into a downward-growing tube (Martin, 1974)
• First filmed forming by BBC Frozen Planet in 2011 · called an 'inverse chemical garden' in 2013 (Langmuir)

Sources: Martin, J. Fluid Mech. (1974); Cartwright et al., Langmuir (2013); BBC Frozen Planet (2011); Scientific American
Note: scenes are AI-generated recreations.

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