Which all doesn't matter at all because it'll recover afterwards. Framing it as an ecological disaster is just a way to engage all the people who are prone to worrying about the environment.
How much damage has to happen before the global environment becomes unrecoverable?
The fact is the majority of penguin species today have declining populations. Those are not recovering. A couple of million of them getting wiped out is unlikely to help reverse that downward trend.
Where the damage in question consists of dumping freshwater into the sea? It would take more water than exists in the world to do irrecoverable damage that way. Try to avoid learning about rivers.
Fresh water has a different density than salt water, and ice melting in the artic and antarctica is resulting in a huge influx of fresh water that can disrupt ocean currents [2]. These currents currently distribute a lot of heat around the world, and them stopping would result in places like europe getting much colder, while other regions would become much hotter (and with the warmer oceans, probably also have extremer hurricanes).
[1] https://www.nationalgeographic.org/media/earths-fresh-water/
[2] https://wikipedia.org/wiki/Shutdown_of_thermohaline_circulat...
That is a _very_ odd definition of a disaster. The Earth recovered from several mass extinction events. Does that mean that they were not in point of fact, disasters? That nothing is a disaster?
It is a localised disaster. Not all disasters have to be on the global scale to have relevance.