What is the effectiveness of the repetition of "is" in lines 1-4 in the poem "Dover Beach"?

Arnold’s poem represents a doubt in both faith and
society, a theme common to the Victorian era. In the first and second stanzas, Arnold
describes the beachsetting in terms of poetic techniques: The rhythm and cadence of the
ocean createa mood. He remarks how Sophocles once heard in those same sounds “athought,”
as if poetic thought cannot help but arise from observations on nature.But Arnold’s
crisis of faith makes it impossible for him to see the landscape asanything but symbolic
of the loss of faith which he believes is breaking apart thesociety of his time.
The repetition of "is" allows the poem to shift from the realistic to the symbolic with
an extreme sense of subtleness. Without the repetition, the shift would be forceful, and
not what Arnold was looking for. This shift from the realistic to the symbolic allows
him to express his idea that a loss of faith is symbolic  for the world, is much more
dramatic and thought evoking.