What would happen if all the ice caps melted?

Actually thousands of square miles of ice already melted thousands of years ago which is why we have the lake we do today.

Fill a glass near to the top with water then add ice cubes to bring it up to the edge.

After all the ice melts, the level will be the SAME.

That's the biggest lie ever told

The amount by which sea levels would rise is quite alarming.  Almost all ports and coastal areas would disappear under hundreds of metres of water.  Without the reflectivity of the ice more heat would be absorbed by the earth and less radiated so we would get an anti ice age.  With vastly less arable land our food production would plummet and many currently inhabited areas would become too hot for humans.  There would need to be a substantial reduction in world population to balance living areas, food production and population.

Sea levels would rise, ocean salinity would decrease, continents would experience some rebound, Florida would disappear, and yes, we would adapt. All life would. It has before; there's no reason it won't again.

Seas would rise, less solar energy would be reflected into space

adjust what?

if all of them were to melt, global sea level would rise approximately 70 meters, flooding every coastal city on the planet,  To know just how far inland the water would go, look at a topographical map of the world and note where the current land is less than 70 meters above sea level.

Kind of depends on how fast.  That is one huge amount of water, after all.  The earth would adjust, and I have to presume that humans would as well, given that our supposedly greatest trait is our capacity to adapt, and to make habitability out of very uninhabitable conditions.

The loss of all ice cover would not end the world.  The world has done just fine with, and without, ice cover.  Neither state is new and unprecedented.

Rapid flooding would be a problem, and individuals would suffer.  But rapid flooding requires rapid melting, and that is not an easy thing to make happen.  Need a lot of heat, a very large amount of heat.  Like impact by a mini-asteroid level of heat.  Daily solar heating is not sufficient.  It could be, over long time periods, cumulatively, but the sun would have to go into major flare mode to cause major ice melting over a short term, and if that happened, ice melting would be the least of our problems.

Many part cities?would go underwater is?what would happen. That includes greater New Orleans. Much of greater New Orleans is sinking. In some areas it is sinking as fast as a half an inch or more?ever year. This based on over 60 years of like experience in New Orleans.