This is where the excess heat has been going for decades. Back in the 90's we hadn't really done any deep water temp assessments and we certainly didn't have historical data for comparison. I was auditing a discussion group with a bunch of Ph.D. candidates, looking at satellite data and watching them being all baffled about where the extra energy (insolation was known, radiative loss was known, delta indicated accumulation) was going. I (non-degree candidate and therefore scum) asked if they had looked in the ocean. They said it wasn't there. I think I invented the facepalm at that point. Water has a very high specific heat, and there's a f*kload of water in the ocean. We only started measuring deep water temps around 2004, and not extensively until within the last 5 years or so. All that energy that was stored (and is still being added to) back over the last half-century or so has been cheerfully flowing along in the AMOC at depth, and is now showing up where we can notice its effects. Just watch those glaciers, baby. We're coming up on the time frame for the industrially-warmed waters from 100 years ago to start working on the edges of Antarctica. Party time.