The growth and structure of sea ice

Question 1

In cold waters, what parameter is most important for density (stratification)?

Answer 1

In cold water, salinity matters most for density

Question 2

Mention 6 properties of water:

Answer 2

1. Highest density at 4◦C
2. Solid phase has lower density than liquid phase
3. Very high boiling point
4. Very high melting point
5. Highest heat capacity of all liquids
6. Very high latent heat

Question 3

In terms of what is

• frazil?
• nilas?
• rafting?
• Pancake ice?
• Grease?(?)

Answer 3

Frazil: As the ocean water begins to freeze, small needle-like ice crystals called frazil form. These crystals are typically 3 to 4 millimeters in diameter. Because salt doesn’t freeze, the crystals expel salt into the water, and frazil crystals consist of nearly pure fresh water

Nilas: Forms during calm conditions. It is a thin sheet of smooth, level ice less than 10 centimeters thick; appear darkest when thin. Depending on the thickness; one have dark and light nilas.

Rafting: Currents or light winds often push the nilas around so that they slide over each other, a process known as rafting.

Pancake ice: If the ocean is rough, the frazil crystals accumulate into slushy circular disks, called pancakes or pancake ice, because of their shape. A signature feature of pancake ice is raised edges or ridges on the perimeter, caused by the pancakes bumping into each other from the ocean waves.

Grease:

Question 4

Does ice grow faster in the basal plane or in the c-axis?

Answer 4

Ice growth much faster (≈100 times) along basal plane than along c-axis

Question 5

What can you say about the shape of consolidated pancake ice?

Answer 5

Bottom topography of consolidated pancake ice is very rough

Question 6

What is the bulk salinity?

Answer 6

Bulk salinity is the salinity of a melted sea-ice sample.

φ: Fraction of pure ice

(1−φ): Fraction of liquid brine

Sbr: Brine salinity (depends only on temperature)