I'm thinking out loud here about a rating system for melt seasons and I'll use 2019 as an example. I'll consider it similar to evaluating a baseball player where a guy like Mike Trout is considered the best because he does so many things well, but is not necessarily the best in any single attribute
Ultimately, ice melts as a new result of it's intersection with heat. There are a lot of ways that can come about.
1. Atmospheric Heat (2019 score 8.5 / 10)
Plenty of early season heat. Recent scorching heat off Siberia. Consistency in terms of maintaining a positive anomaly throughout.
2. Ocean Heat (10 / 10)
The Pacific side is off the charts and the Atlantic is sporting a 0.5C positive anomaly.
3. Insolation / Albedo Reduction (8.5/10)
A fair amount of high pressure systems and early season open water.
4. Wind damage (6 / 10)
The Beaufort cyclone is a good example of this. Turned the gyre into rubble. Exposed a lot of surface area to ocean heat. We've also seen a tailwind pushing Laptev open water toward the pole and are now seeing Pacific water coming through the Bering Strait.
Not in the league with the 2012 GAC.
5. Export - Wind and Current (10/10)
Nares has been open. Fram has been steady. Perhaps the most important feature of the season has been the wind assisted push of ice to warm water to the Beaufort, Barents and Fram.
6. Rain (1/3)
Not much rain to speak of this year.

7. Starting Point (4.5 / 5)
2019 started the year from a low max. Less work to do.
8. Intangibles / Momentum (2/2)
Here's a category that gives the reviewer a little bit of leeway. I'll give 2019 some bonus points for strong momentum and no letup.
All in all, we come up with a score of 50.5 out of 60 possible and that is for a season that is ranking among the leaders in many categories.
This is just a straw man / food for thought. It's clear that there is a challenge in evaluating a season and benchmarking vs prior years. A system like this is intended to steer the focus toward the root causes of the end result and is easily accessible in terms of understanding.
No pride of ownership here. If someone sees a useful variant of this, feel free to run with it.