I need help interpreting the poem "Pursuit from Under."

First let’s try to pin down exactly what’s going on in the narrative of the poem before we break it down further into its more poetic meaning. We have a man walking through the grass, presumably on land near his father’s estate. He remembers reading the journal of some arctic explorers who died of starvation. He pays close attention to one journal entry in which the explorers describe the behavior of a killer whale beneath the ice. He fixates on the terrifying image of this creature stalking you from the depths and rushing up to attack. He then superimposes this image, this fear, into his own life on a farm.
Now that we’ve discussed the basics, let’s get into what the poet means by all this. What is the significance of comparing the experience of the arctic explorers to the narrator’s own life? Well, the narrator seems haunted by the encroaching imminence of old age and death. For instance, in the second stanza, he mentions an ice age (usually connoting death) coming up through his feet while he is trying to emulate the way he behaved as a child, trying to hold onto things as they always were. Interestingly, it is not the blank page from the explorers’ journal (signifying their death by starvation) that scares him most. Rather, it is the entry describing the shadow of the killer whale hunting them. It is not the whale that ultimately kills them, but this specter under the ice is still what frightens the narrator the most. This could imply that he’s not so much scared of death itself but actually of the fear that the idea of death brings with it.