This is peak...something‽

Extremely cold/dense water underneath Antarctic's floating/shelf glaciers sinks to the bottom & flows North. The sinking of the water pulls in more water under the glacier, and this interaction drives the system.

The deep cold currents split & keep heading North until they upwell in various places, and this helps to cool the environments in which these events occur.

The sudden collapse of a floating/shelf glacier would instantly shut off the system that keeps the water flowing. The upwelling may occur for a short time after, just from momentum, but the 'pressure' driving the system has been cut off.

The effected environments would suffer rapid heating; with attending biological disasters.