Warming = less ice = more plankton = CO2 storage = less warming?

Just preliminary evidence here, but the British Antarctic Survey has found that the way melting ice allows more sunlight to shine in the ocean spurs significant blooms of tiny marine creatures. Those phytoplankton, in turn, eventually die and sink to the ocean bottom, taking carbon with them.
That means a symptom brought on by greenhouse gases, the melting of the ice, could spur a phenomenon that reduces the levels of those same greenhouse gases in the atmosphere.
Bad news: it doesn't look like the effect is anywhere nearly dramatic enough to offset the overall buildup of greenhouse gases.