In the winter, how come water nearest to land is more likely to be frozen than open water?

I was on a plane and I saw that water near land was frozen, but when out in the open it was still liquid. Why?


land will get to temps below freezing and the near shore has less mixing with the open water (when water gets near freezing, it tends to mix with other water and distribute the lower temperature across a large volume, thus "raising" the temp in the immediate location of heat loss). this is most obviously seen in flowing streams. Also, it is easier to maintain the solid structure where there is less physical agitation that could break up any solid that does try to form. Zones with little wave action will freeze faster. Part of that is the mixing thing in process, and part the mechanical destruction of any "sheets" which might form. There is also a modest "nucleation" problem. The ice likes to have a solid surface to start its crystallization. Same thing with snow, actually. Snow forms around dust particles in the air. Once the ice forms a layer, then more ice forms on top of it (outward in the case of shoreline ice).


Shallow water will get colder and freeze much more readily than deeper waters. Shallow water doesn't hold as much energy as deeper waters and at low temperatures ice will form where it's the coldest first. The properties of water are very unique and neat.


It's because the land is solid and acts more of a heatsink than the water.