What's a word that means, "someone who alerts others in an emergency or alerting in general,"? i thought, 'alerter,' was a real word lol.

Along the sea-sands damp and brown the traveller hastens toward the town, what is the effect of the enjambment in these two lines? it emphasizes the idea that each line is a separate thought. it creates a rhyme scheme between the two lines. it encourages the reader to pause between the two lines. it strengthens the connection between the two lines.