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University of Bergen
Geophysical Institute

24 days of kitchen oceanography

Each day a new experiement will be posted here. Reveal what is hidden behind the windows by clicking on the arrows below.

Introduction
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Day 9
Day 10
Day 11
Day 12
Day 13
Day 14
Day 15
Day 16
Day 17
Day 18
Day 19
Day 20
Day 21
Day 22
Day 23
Day 24

Main content

Fresh water and salt water ice

Day 18
18.12.2020

Why does the pink color run off of one of the ice cubes but seeps into the other?

Isbit av ferskvann til venstre og av saltvann til høyre.
Photo:
Mirjam Glessmer, GFI

Experiment 18:

We freeze two ice cubes, one from salt water, one from fresh water. The two show very different structures: While the fresh water ice cube forms a very uniform ice structure, the salt water ice cube has a sponge-like structure. During ice formation only the water molecules freeze together as regular ice crystal. Salt is rejected from the crystal and pushed as very salty brine into channels that don’t freeze. If you drip color on the ice cubes, it can penetrate into these channels like a sponge.

Chapter 18: Fresh water and salt water ice

This type of stratification, with colder and fresher water over warmer and saltier water also occurs in the Arctic. There, the stratification is formed by both, precipitation and when sea ice melts during summer. Sea ice, even though originally formed from salty seawater, consists almost exclusively of fresh water.

Prepare for day 19:

Dissolve some food dye in water, put into ice cube tray and freezer to create colored ice cubes.