Right, so you have high insolation for some number of days. This provides heat at a rate of 300-500 W/m2 at peak, but that peak drops off, so the average insola

Right, so you have high insolation for some number of days. This provides heat at a rate of 300-500 W/m2 at peak, but that peak drops off, so the average insolation over the course of the year is low in polar areas. This is a positive feedback of open water (albedo ~.1 vs ice ~.6) and is limited by the duration of high insolation over open water. The maximum insolation is at the summer solstice (June) when there has been a smaller decline in arctic ice area (10%? http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/ http://nsidc.org/arcticseaicenews/charctic-interactive-sea-i...) By the date of low ice extent in September, the sun is getting pretty low for polar areas (low angle, low duration, low insolation - see the equinox data in your link: http://www.applet-magic.com/insolation.htm http://www.applet-magic.com/insolation.htm) Open water loses heat much more rapidly than ice-covered water, with the rate dependent on temperature, wind speed, etc. One study found open water heat flux was about 250 W/m2 vs 75 for ice pack in March/April (http://onlinelibrary.wiley.com/doi/10.1029/94JC02485/abstract http://onlinelibrary.wiley.com/doi/10.1029/94JC02485/abstrac...). I didn't find references to give averages or graphs over a year. However long the ocean remains open, it radiates excess heat at an increased rate vs ice pack - a negative feedback of open water, limited by the area and duration of open water.