What is the tone of the first eight lines?

In the first eight lines of Christina Rossetti's sonnet "Remember," this tone is solemn, somber, and melancholic. The narrator is asking her beloved to remember her after she dies.
The tone is supported by the slow-moving lines. Repetition, for instance, slows down the first two lines as the speaker repeats the haunting words "gone away . . . gone . . . away," which toll like a funeral bell. Further, the repeated phrase "remember me" in the first, fifth, and seventh lines also tolls like a bell and sounds like a ghostly refrain, slowing down the poem.
The image of "the silent land" also adds to the solemn tone of these lines: silence is somber, and the term "silent land" refers to the land of death and the grave, a melancholy subject.
Finally, in the last line of this part of the sonnet, the solemnity of the dead one's separation from the living is emphasized in the words of address to the beloved:

It will be late to counsel then or pray.