1. PIOMAS = Pan-arctic Ice Ocean Modelling and Assimilation
Mid September
An exponential fit is in good agreement with model predictions. There is a 50% chance of a few days with almost no ice in September After that the zero happens earlier and the restoration later every year. This will increase methane release to overtake CO2 as the main climate driver.
NOAA
There are lots of real ice thickness measurements to compare with the PIOMAS model predictions. There is an underestimate of thick ice and an overestimate of thin ice so reality is worse than PIOMAS.
Surface melting exposes layers of black carbon and volcanic ash with much lower reflectivity than fresh snow. We can multiply the solar input by the change in reflectivity to get numbers in watts per square metre in remaining ice and the surrounding land mass. The mid-summer input at the North Pole is 100 watts/m2 more than at the equator.