Wouldn't erosion cause sea levels to rise?

[Ecky]

My background as a geologist inclines me to say, "most likely yes". Sea level rise will, on average, slightly increase erosion. Erosion will slightly increase sea level. I couldn't tell you the magnitude of these changes, but my bet is that on a human timescale, eroding land will have a much smaller effect than melting water.

[Xist]

Originally Posted by freebeard

Your linky-dinky is unresponsive to the question

Not the first sentence?

"Erosion and sediment transported by wind, water, and ice can deliver sediments to the ocean and, although the impact is seemingly small, when averaged globally, a significant volume of sediment is delivered, and this can displace an equally significant volume of water."

Ecky,

Yay! I was right about something!

[freebeard]

Oh, come on. Sea level is a datum line.

The reducto ad absurdum: If all the terrain above sea level eroded into the depths would sea level be higher or lower than it is now?

[Xist]

It would be sea level.

[freebeard]

By Jove, I do believe he's gotten it.

[NeilBlanchard]

Originally Posted by jamesqf

That's just plain wrong. Sea level is defined WRT gravitational equipotential surfaces (plus a small contribution from the centrifugal force of Earth's rotation), NOT distance from the center of the Earth. If the sea level was 8000' higher south of the equator, the water would flow north until the levels equalized.

Did you read the link? It is all about how measuring mountains above sea level is not very accurate, in telling us how tall they actually are above the center of the earth - or how close they are to space.

There is about 2.5 miles of ice on Antarctica. We have the GRACE satellites that can measure gravity very accurately.

[jamesqf]

Originally Posted by NeilBlanchard

Did you read the link? It is all about how measuring mountains above sea level is not very accurate, in telling us how tall they actually are above the center of the earth - or how close they are to space.

Yes, I read the article - skimmed it, rather, because I'd seen similar before. The problem is that it's what I might call junk science news, like "supermoons": something that is factually true, perhaps even sort of interesting, but absolutely irrelevant for any practical purpose.

Just to note: those equatorial mountains aren't closer to space, because space is defined either as lack of atmosphere (for practical purposes) or for legal purposes as the Kármán line, which is 62 miles/100 km above sea level. And sea level, of course, is defined as the approximately oblate spheroid that's a gravitational equipotential surface.

The same principle holds for Antarctica (and Greenland, or anywhere there are tall mountains, deep basins, or rocks of different density). Yes, they have gravity, but that gravity defines the (non-spheroidal) equipotential surface that is sea level. So the water there is not 8000' higher: it's all at the same* gravitational potential.

*Neglecting the small effects of winds, currents, and the like.

[freebeard]

What NASA has to say on the subject:

https://vesl.jpl.nasa.gov/research/sea-level/

[Xist]

Distance from the center of the Earth?

[freebeard]

What happened between #14 and #19? You were so close, go back and reread #17:

Originally Posted by amesqf

And sea level, of course, is defined as the approximately oblate spheroid that's a gravitational equipotential surface.