‘Blacked fingertips’ gives me an image of the narrator trying to move his fingers, having difficulty doing so, then looking down at his blackened and disfigured fingers.
‘The mountains held me in thrall’ this gives me an image of the narrator being surrounded by mountains on all sides, with what feels like, to them, there is no escape from them.
‘I gazed across at the icy white sweep of Sarapo’ This makes me think that the narrator is looking longingly at the summit of the Sarapo, one of the mountains around their campsite.
‘Bitter’,bitter was added because it adds feeling and depth to the compared to just have ‘feelings’, it makes it easier for us,the reader, to connect with the feelings of the narrator.
‘Deep’,deep means very intense or extreme, this was included to helps us understand just how tired and exhausted the narrator was, and therefore how rejuvenated he was the next day.
‘Sweep’, sweep is a word that gives us an image in our heads, I believe that it was used to give us a clear image of how the mountain, Sarapo, looked.