I came across this brilliant Deep Sea News blog post about oil on troubled waters. It talks at length about how a surface film of oil damps out higher frequency surface waves and only the low frequency waves can propagate. The net effect is the sea feels calmer as the breaking waves are damped out.
The same thing happens in rough seas when ice forms. I took the picture below in Bellingshausen Sea.
What you are looking at is very thin slick made up of sea ice crystals in the open ocean (called grease ice). The layer of crystals only allows the low frequency waves to propagate - so you see these odd looking slowly propagating ripples.
It does look like there is oil on the surface doesn’t it.
When the wind picks up slightly and it "tears" the grease ice slick, instantly tiny wind generated waves start to form
The effect is very clear. The next picture is an enlargement of the boundary showing the high frequency wind generated wave being damped out - and refraction at the boundary between the open water and the ice/ocean mix.
This damping out means (as you can see) that the reflectivity of the ocean surface is very different between areas that are open water, and areas that are ice covered.
That means you can easily observe it from space using satellites with radar sensors in the same way that for example oil slicks as sea can be observed. For example this shows an oil slick.
The oil spill shows up as dark - just as the sea ice does in such imagery.
There are some very interesting science papers in this area, and several pdfs showing how you can observe this effect from space