[dangirsh]

I think the image is trying to convey that there's a rising immediately near the glacier due to the tectonic plate lifting up. Then there's a falling due to reduced gravitation. What's not shown would be (much further away) a rising due to increased water volume.

I agree that the image is a bit confusing.

[strogonoff]

I think the green line is the sea level after the melting, since it is labeled Final Sea Level. It does not show a fall, only a rise, next to the glacier.