Diminishing ice cover has increased political and economic competition for resources inside the Arctic Circle. This means more submarine operations, which are doubly claustrophobia-inducing, as a sub can only surface where the ice is comparatively thin. In an emergency, finding the nearest hole in the ice is essential, and this has spurred the development of a new type of forecast.
There are two types of hole in the ice, known as leads and polynyas. Leads are long fractures, gigantic cracks caused by ice sheets moving apart. Ultimately, they are due to wind or ocean currents pushing areas of ice in different directions. Leads are generally transient, as the seawater freezes over quickly when exposed to the cold air.
Polynya is the Russian word for an ice hole, and it describes an area of open sea produced by an upwelling of warm water. This melts the ice cover above and creates a gap in the ice which typically remains in place for longer than a lead.
As part of their Arctic Cap Nowcast/Forecast System (ACNFS), the US National Ice Centre produces a Flap (Fractures Leads And Polynya) forecast for submarine operations, based on satellite imagery. This shows current conditions and predicts areas of open water five to seven days ahead; having a prediction before they sail is useful, as a submerged submarine cannot receive radio updates.
The Flaps forecast has a claimed accuracy of around 88% and may prove vital for future Arctic operations.