you might enjoy the book Earth by David Bryn. I liked it because it has gravity waves and transhumanism. OOO i just remembered also voluntary reversible sterilization as like, birth control. I can't remember if the Garbage Patch was a new continent or just a city, but i think it featured in the book. I will say no more because spoilers, it's best to discover the book yourself. I think i last read it a decade ago.