Hi all! I defended my Ph.D. thesis back in 2019 and I also served as the creator and moderator for the subreddit r/FluidMechanics for a long time. I think with that I have gathered enough experience and courage to answer some of your queries. Some broad topics that I can answer questions on are:
computation fluid mechanics
scientific programming and HPC
nonlinear shallow water equations
statistical description of turbulence: spectra, energy budget etc.
Not just the Gulf stream, but the whole Atlantic Meridional Overturning Circulation (AMOC). AMOC, as you may know transports heat keeping the tropics cool, north warm and melting the Arctic. From what I understand the observations are only a few decades old, but it suggests the AMOC has been slowing down.
As an extreme case (and I repeat extreme) scenario it begs the question would it shut down or flips direction. Theoretically there are "thermohaline" circulation modes where that may happen. Paleoclimate evidence suggest that there were times that there was no AMOC and we had a PMOC (a Pacific one) instead. So many open questions...