Slightly off topic - in the Sub-Polar Gyre, an argo float has observed (I believe for the first time this season) the mixed layer reaching below 1000m depth - and it goes right down to 1600m.
(This is effectively the floor - below roughly 1600m there is an abrupt increase in density across the whole SPG)
Float ID 4902396, Date 20180221, Time 0900, Lat 57.700N, Long -53.635E, Salinity ~34.85, Temperature ~3.1C at the surface increasing to ~3.2C at 1600m.
FWIW I think this is happening later in the season. Compared to last year anyway. (Is the whole SPG surface anomalously fresh this year?). But this Argo profile verifies the cold spot in this location at 1000m depth on Mercator Ocean.