The mystery of ice
4th August, 2015
Asking someone 'what is ice?' may seem like a relatively simple question. There is a good chance you will receive lots of answers along the lines of 'frozen water'. However, the truth is that ice, especially that forming on large expanses of open water, can take on many different and incredibly beautiful forms.
These different forms of ice are defined into categories by The World Meteorological Organisation depending on their origin, size and shape. Some of the more unique and fascinating types of ice include:
- Frazil Ice
Frazil ice resembles slush and is the first stage in sea ice formation. It will generally form on open, turbulent and supercooled waters such as rivers, lakes and oceans. Supercooled water occurs when the water surface loses heat quickly and frazil ice therefore commonly forms on clear nights, when the temperature has fallen below -6°C (21°F). Strong winds or the flow of the water will cause the supercooled water on the surface to mix at all depths and the small frazil ice crystals get dragged from the surface to the bottom where they quickly multiply in number. As the ice crystals grow in size, they adhere to objects in the water and over time accumulate together and block the water.
- Grease Ice
When a thin layer of frazil ice crystals become clumped together they form what is known as grease ice. This is the second stage in the formation of sea ice and gets its name because the water's surface resembles an oil slick.
- Pancake Ice
Depending on the local conditions which impact upon the formation of ice, pancake ice consists of round pieces of ice which vary in diameter from 30 centimetres to 3 metres. Each 'pancake' can be up to 10 centimetres in thickness and will commonly have elevated rims as a result of collisions. One of the most common ways in which this is formed is on water covered in grease ice.
- Bergy Bits
Most of you will be familiar with an iceberg, but bergy bits maybe less so. They will usually rise between one and four metres out of the water and are small icebergs, fragments of an iceberg or pieces of floeberg which are in the latter stages of melting. Whilst 'bergy bits' may sound like a cute name, they pose considerable danger to shipping due to being a lot more difficult to spot than larger icebergs.