Firstly the earth has had no glacial, mountaintop or polar ice whatsoever, none, for 90% of its history. Including the geologically incredibly recent conditions before the current ice age. Secondly if all the ice and snow in the world melted, every ounce of it, se levels would go up less than 70 meters. 90% of the current dry and arable landmass of earth would still be here. Nothing can make just "two continents" except for continental drift creating amalgamations and super continents, and that will be over tens of millions of years, and there would be roughly the same dry land and sea covered ratio.
I just mention that because a couple of the people involved in the making of this have bizarrely claimed the set up of two small remaining patches of dry land is a "warning" due to climate change, when that is absurd.
The general human premise, of an distant rare and isolated military or colonial outpost or outposts, though would be a better premise and has served a lot of good literature. Greek poet Constantine Cavafy long form poem served as inspiration for the novel "Tartar Steppe" and the recent "Waiting for the Barbarians" with Johnny Depp, Mark Rylance and Robert Pattinson.
Those are good treatments of this idea. This dumbed down "Last Sentinel" is just mind numbingly bad. The plot twists become tedious, and in fact are so telegraphed as to be cringe. No one in the film can act. And you will be checking your watch every five minutes as more and more boring and pointless filler plods by.
3/10.