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MCMLXXXII t1_j1hwuqq wrote

The usual reason for coastal flooding is low atmospheric pressure. We might not even think of it but air has mass and it is usually weighing down on the oceans and keeping it compressed. The air when there is low pressure is less dense so there is less weight pushing down on the seas. This causes the previously compressed water to expand and that is why the sea level rises slightly. This is most notable during times of hurricanes as they are very large low pressure systems.

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fruit__gummy t1_j1i6ukz wrote

I’m not sure the water “decompresses”, I think it’s more like, higher pressure regions of the ocean push up lower pressure regions of the ocean. Think hydraulic pistons etc.

Water is pretty incompressible. If it wasn’t, a gallon of water at the bottom of a swimming pool would weigh more than a gallon from the top, but this isn’t actually true in real life

So water isn’t actually “expanding”, it’s just being pushed up by regions of the ocean with higher atmospheric pressure

I could be wrong but this is my understanding

Edit: actually pretty much every part of your comment is wrong lmao. Why do you speak with such authority on things you have no clue about

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HElGHTS t1_j1kyc6d wrote

I think the parent comment is using "compressed" to mean "being forced elsewhere" as opposed to the more typical "being forced into having less volume" which would be exactly what you're also saying. I don't condone imprecise language but I'll give the benefit of the doubt because it's pretty intuitive that water is hardly compressible.

Think about using a compression bandage or compression socks. You're not literally compressing, you're just squeezing the flesh and it goes elsewhere.

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fruit__gummy t1_j1l5129 wrote

I think OPs use of the word “expand” means they were using your second definition of compress. Also don’t compression bandages cause your veins to compress/reduced cross sectional area?

Also they are just straight up wrong about this being the cause of the flooding, as other commenters have pointed out

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nasty_brutish_longer t1_j1i6xf2 wrote

Sort of. High pressure areas of a storm can "bulge" seas into low pressure areas, but most surge force by far is from wind moving in the same direction.

Atmospheric pressure is absolutely a thing on this planet, but the difference between typical high and low pressure systems isn't that great compared to the total mass of air.

*Edited to add link and remove "compress." As another poster points out, water is essentially incompressible.

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HudsonRiverMonster t1_j1iulcb wrote

Confidently wrong. It rained and snowed a lot, this is storm water from the Hudson Valley flowing out into the sea. Combined with the tides, that drives up the river level much more than a dip in atmospheric pressure. This isn’t a tropical storm, and that’s not how tropical storms cause storm surge anyway.

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_switch360_ t1_j1kezht wrote

Hey the Science guy wanted to sound smart about decompression of water to impress the chicks.

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_switch360_ t1_j1iapgy wrote

Or the torrential rain that caused extensive runoff up river because of the snow melt.

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