Always a pleasure, trying to find fault with a ribbonning image...but I'll try ;-)
Absolutely breathtaking capture of the aurora borealis. Love the front-to-back dof...or did you use focus stacking? The play of the lights on the ice especially is just fantastic; they are so fluid in the sky then look more jagged on the ice. Wonderful. Gorgeous otherworldly tones in the sky, barely any star blur...btw I assume you mean a 1/15th of a second exposure? It would seem to me that at ISO 1600 and 15 seconds you would definitely have some blown areas, but none that I can see here. Canon's ISO is the one thing about that brand that I truly envy :-)
What would I change about this image? If I were lucky enough to be there I might try something rash like a circular star blur, which would take a few minutes. If you had the lights going that night too, could make for some really trippy effects.
Keep up the great work and congrats on the yellow!