Influence of polynyas on deep water formation

Polynyas are primarily open water sea ice free areas surrounded by sea ice, formed by either strong winds or oceanic currents that drives away the sea ice. There are two types of polynyas: coastal polynyas (very thin ice present) and open water polynyas (no sea ice). For both types of polynyas, it is the direct contact between the atmosphere and the water that leads to the formation of deep water. Indeed, the water will cool much faster in polynyas thanks to the absence of sea ice or the presence of very thin sea ice, thus the water will be denser and even more so with the salinity released from the surrounding sea ice. The two main areas for deep water production are the North Atlantic (North Atlantic Deep Water (NADW)) and the Southern Ocean (Antarctic Bottom Water (AADW)).