Some quotes from https://www.science.org/doi/10.1126/sciadv.adz2555
I feel are particularly important.
Both, for understanding the #AMOC situation 17 to 11 million years ago (short: Ma), and for understanding the weaknesses in #EquilibriumClimateSensitivity when it is in part derived from such periods as the mid Miocene, in low CO2 ppm but high "global mean °C".

* open/close ocean throughways are "difficult to date with the precision"

Roughly coinciding changes:
* deepening of the Greenland-Scotland Ridge (GSR) [near Iceland; important location for today's AMOC down-welling]
* altered Canadian Arctic Archipelago (CAA) gateways
* closure of the Central American Seaway (CAS), [ie Panama]
* shallowing of the Tethys Seaway [Indian Ocean to Mediterranean]
* Antarctic ice sheet (AIS) retreated substantially during the MCO