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Comment by jackcarter | Hacker News Reader

Won't post-glacial rebound counteract rising sea levels?

Unfortunately no, not here. The metaphor I've heard is continent as couch cushion: the glacier was "sitting" on the upper part of North America, pushing up the edges. Now that weight is gone, the coasts are dropping slightly.

Ah, that’s interesting and believable. Do you know where you heard that?

I found this article, which talks about a slightly different effect: If Antarctic ice melts more quickly than arctic ice, then the Antarctic land rebound will shove southern-hemisphere water north, raising sea levels in the northern hemisphere. The opposite effect happens if arctic ice melts before Antarctic ice.

https://www.theguardian.com/commentisfree/2018/oct/01/cities...

The article doesn't even mention the effect of gravity, which is also significant. Ocean water is currently gravitationally attracted to the ice caps, and when an ice cap disappears, all that "bunched up" water will spread around the globe. This effect reduces sea level rise in a large area around the ice cap, and increases it everywhere else.

This other article in The Guardian does mention it: https://www.theguardian.com/environment/ng-interactive/2018/...

Here the Woods Hole oceanographers talk about it without the couch analogy:

https://www.whoi.edu/news-release/why-is-sea-level-rising-hi...

If it's sitting on top, wouldn't it push down? Or do you mean upper as in north?

It’s fantastic and even mildly hilarious that this is a real effect at such a massive scale.

It depends on where you are. If you were underneath the ice sheet (which is Long Island and further north), then you are rebounding since the ice was pushing down on you. If you were further south, then you are slowly sinking due to the rebalancing of weight.

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