Atheism is nothing to do with life after death - it's only a lack of belief of gods.
I personally have no belief of any life after death, as that is, after all, what "death" means. While there are a zillion fantasy situations that cannot be disproven, it is nonsensical to believe them because:
a) many will be contradictory, and it is ludicrous to believe both, and meaningless to try to choose,
b) all are indistinguishable from untruth.
That's why I feel we should only accept that for which there is actually evidence, assuming we do actually care about truth.
To date, there is no reliable evidence to indicate the human consciousness can survive death, so I have no belief it does. Indeed, out current understanding of consciousness is that it is a function of the brain, so ends when the brain ceases to function.