How is the notion of death or mortality presented or treated in The Great Gatsby?

Fitzgerald uses foreshadowing to point to the deaths of both Myrtle and Gatsby at the end of the novel. Myrtle will die in the Valley of the Ashes when Gatsby's car hits her, and ashes themselves are a traditional Christian symbol of death. Fitzgerald foreshadows the type of death she will experience when two cars get into an accident while trying to get out of Gatsby's long driveway after one of his parties. Nobody is killed, but the car accident is a portent of what is to come, especially when the person accused of driving one of the cars denies that he was the driver.

When Nick drives into the city with Gatsby for lunch, they pass a hearse "heaped with blooms." Nick spends time describing the seemingly inconsequential details of this funeral procession, which should alert the reader that death will reemerge as a motif. Further, the word "ghost" or "ghostly" appears ten times in the novel, mostly in conjunction with Gatsby. This associates him with death. Nick, for example, describes Gatsby's "ghostly heart" as Nick imagines that even to Gatsby, Daisy must have fallen short of his dreams. "Ghostly" is used three times in conjunction with Gatsby's parties: once during the above-mentioned accident, once when Owl Eyes laughs a "ghostly" laugh, and once when Tom and Daisy see a "ghostly" celebrity. It's also used in conjunction with his home: first, after Gatsby ends his parties, Nick "tumbles" on the keys of a "ghostly" piano. The morning of Gatsby's death, "ghostly birds began to sing among the blue leaves." As Wilson approaches to shoot him, Nick imagines Gatsby must have been floating in his pool contemplating a "new world ... where poor ghosts ... drifted fortuitously about."

Throughout the novel, broader hints of mortality weave in and out, such as the sense that Tom's glory years were during college, long behind him, and Nick's sadness as he turns 30 that the best part of life is drifting away from him. We are all getting older, closer to death, the novel says, while yearning for bygone days, beating on, "boats against the current, borne ceaselessly back into the past."