It's not sea ice melting, though that happens. That changes the temperature f the sea and its salininity therefore density, so currents move about.
The water's warming so it expands - that's half that 20cm rise.
Glaciers and antarctic ice sheets are melting, adding water.
It's predicted to be 2-3 feet ( I forget, look it up) by 2100.
The last 3 inches of the rise has been only since 1980 or something.
I've been to several areas where they stick markers in at the edge of the glacier every year, and it's shocking to see, when it's like 400m metres back in a few years.
Once the ice is gone the albido (reflectance) drops so it gets warmer in the sun, and things stay melted.
You get relatively small changes in sea currents which affect the weather (as in El Nino/Nina) which affects the rainfall which disturbs something else.......... .
If the Greenland ice sheet carries on melting, adding dense cold water to the north atlantic, it's expected to divert the gulf stream, or disperse it. If it flips to another route it may never come back, because it could change the weather, yada yada yada....
We're the same latitude as Newfoundland and Labrador, = bloody cold, so without the gulf stream, chilly.
The "great" ocean currents go round just north of Antartctica, as there's not much land. Little offshoots, coriolis effect, annual temperature changes etc, contribute to currents which set weather patterns worldwide. They've been getting disturbed and moving hurricanes onshore, etc, , more is predicted. It's like there's a set of oscillations set up, which sets the normal range of variations, and by warmng things up we're giving the system a squeeze. Everything changes a bit, but here and there, things will pop. A heavier sea has more momentum, so the tides timing and range change, and on and on.
Dustbowls have happened naturally, awful. Expect things like that to be climate driven. A few dry years mean the crops fail, the animals die, the people get elephants in their farms, etc, and that's that, desert in just a few years. If you look at weather patterns that's what we've been getting, several extreme years in a row one way or another.
FLoods, famines, wars as a result, lovely. I/we won't be here. It would be interesting to pop back every 100 years or so.