The Arctic's persistent windows of open water are engines of global climate

Countries & Cities · Published 15 October 2026 Swipe more like this →

In short: In the frozen polar seas, polynyas are semipermanent areas of open water surrounded by sea ice. These features, first identified by 19th-century explorers, are not just gaps in the ice. They act as dynamic engines that produce new ice and potentially drive global ocean currents through the rejection of salt.

Derived from a Russian word for a natural ice hole, these features are categorized into two primary types: coastal and mid-sea. Coastal polynyas typically lie just beyond landfast ice—ice anchored to the coast—and are often created by strong winds pushing ice away from the shoreline. Polar explorers first adopted this term in the 19th century to identify navigable sea sections. These areas can remain partially or totally ice-free despite being in regions usually covered by frozen sheets.

Mid-sea polynyas occur more sporadically in the middle of the pack ice, often triggered by specific atmospheric conditions like polar cyclones or cold fronts that push ice in opposite directions. These areas are not merely gaps in the ice; they are dynamic centers of ice production. One famous example is the Weddell Polynya, which was first observed in September 1973. This specific feature has recurred in several subsequent years, including 2017.

Latent heat polynyas, specifically, are formed by katabatic winds driving ice away from a fixed boundary. This process creates a cycle where new ice forms in the open water and is then herded downwind to consolidate with the existing pack ice. Because of this high rate of production, latent heat polynyas are considered major sources of sea ice, particularly in the Antarctic. Beyond ice formation, polynyas play a critical role in global oceanography. They are potential sites for dense water production. As sea ice forms rapidly within a polynya, it rejects salt into the surface waters. This brine becomes dense and sinks, potentially driving the thermohaline circulation—the global The process of brine rejection occurs because the high ice production rates within these zones push salt into the surface water. Scientists are currently investigating whether Arctic polynyas contribute enough dense water to significantly influence global circulation. Additionally, these areas are active sites for the formation of frazil, grease, and pancake ice.

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