Thats interesting, I was aware of the effect of freshwater supposedly slowing or shutting down the heat pump of the ocean by basically stopping the gulf stream...
As far as the ice cores, pick up a book called 2mile time machine by Richard Alley... great read on the Greenland Ice core project, and yes it is an annual record like tree rings...
There are some interesting ideas you brought up, I wasnt aware of a bunch of them and will require further review
I like this thread