This area of the world is one of only a few places where the underlying ocean column is marginally stable enough that this process can occur in the open ocean and lead to convective chimneys going down 2000 to 3000 meters. (realclimate.org)
So if there were no halocline in the Arctic Ocean, the entire ocean column would have to cool to -1.8 C before its surface could freeze (Note 11.5). (www-das.uwyo.edu)
Quick recovery is consistent with the Southern Ocean - centric picture of the global overturning circulation (Fig. 4; Talley, 2013), as the Southern Ocean meridional overturning circulation (SMOC), driven by AABW formation, responds to change in the vertical stability of the ocean column near Antarctica (Sect. 3.7) and the ocean mixed layer and sea ice have limited thermal inertia. (realclimate.org)