Sea Shorts: Lifting the fog... or is that mist?

There’s something beautiful about early morning fog over the ocean. The water is often calm, the air cool and still. But are you sure that’s fog you’re looking at and not mist?

How fog and mist are born

Both fog and mist are created by water vapour which cools and condenses onto tiny particles (like dust or ice), forming tiny water droplets that stay suspended in the air. The sea is always throwing water into the air, and that water contains tiny salt crystals. These salt crystals become the linchpin for water vapour to condense on. But salt isn’t the only type of ‘cloud condensing nuclei’ or ‘cloud seed’ to create coastal fog. Back in 2008, Dr Frithjof Küpper and a team of scientists discovered that when the brown kelp species Oarweed (Laminaria digitata) gets stressed, they release iodine to ‘detoxify’. The resulting iodine particles also act as a cloud seed!

Regardless of the type of cloud seed, fog and mist are essentially just very low lying clouds The key difference between mist and fog is in the density of water droplets, with fog having a higher density than mist.

Fortunately to tell the difference between the two you don’t need to start doing some fancy scientific experiment to measure the density of water droplets. All you need to do is know how far you can see through it. Officially, the internationally agreed boundary where mist ends and fog starts is 1,000 meters. If you can’t see beyond 1,000 meters then it’s fog. If you can, it’s mist.

An early morning ocean view at Newfoundland’s Bonavista Peninsula - with mist (not fog!). Credit: Samantha Andrews/Ocean Oculus.

An early morning ocean view at Newfoundland’s Bonavista Peninsula - with mist (not fog!). Credit: Samantha Andrews/Ocean Oculus.

Foggiest Place in the world

Fun fact - the foggiest place in the world is just off the coast of Newfoundland, Canada in an area of the Atlantic Ocean called the ‘Grand Banks’. Here, the somewhat frigid Labrador Current meets the balmy Gulf Stream. It isn’t the meeting of the currents per per se that causes the fog, but rather the air temperature and moisture content of the air above them. The air above the Gulf Stream is warmed by the current - and has a fair bit of moisture in in. The air above the Labrador Current on the other hand is cooled by the current. When the two air-masses meet, the Labrador Current air cools the Gulf Stream air, causing its water vapour to condense and voila - the area is 'blessed with over 200 foggy days each year.

The warm Gulf Stream meets the cold Labrador Current at the Grand Banks. The result - over 200 days of fog each year! Credit:  Treeman/Wikipedia  ( CC BY 2.5 )

The warm Gulf Stream meets the cold Labrador Current at the Grand Banks. The result - over 200 days of fog each year! Credit: Treeman/Wikipedia (CC BY 2.5)

The Sea Shorts series offers tiny glimpses into all things ocean and coastal. Read more Sea Shorts and other stories here.