Global Sea Level Rise Map | Hacker News Reader

Global Sea Level Rise Map

geology.com

60 pointsperugolate32 comments

It seems to me that maps like this are not very useful, and understate the problem. They treat sea level as something that only varies over long periods of time, ignoring daily and weekly variations.

The major problem with a 1m sea level rise isn't that land which is currently 1m above sea level becomes permanently flooded. The major problem is that land which is 2m or 3m or 4m above sea level becomes flooded way more often.

Local sea levels vary with winds, tides, and perhaps more importantly storms. A smallish rise in sea level might mean that catastrophic storm surge goes from a 500-year event to a 10-year event (numbers pulled out of my nether regions, just meant to illustrate the idea).

For example, much of the damage from Hurricane Sandy was caused by its huge 13ft storm surge. If sea level rises by 1m, then a storm with only 10ft storm surge will match it, which means damage on that level will happen way more frequently, and a repeat of Sandy would be vastly more damaging.

I think what a map like this needs is a setting which shows where the (for example) 100-year flood level is now, and where it moves with the given sea level rise. This is way more complicated, of course, but would do a much better job of showing the real problems.

To see what an x-metre sea drop looks like - https://what-if.xkcd.com/53/

There used to be a place called Doggerland in Europe: https://en.wikipedia.org/wiki/Doggerland

The 200 and 500 metre maps show the Netherlands conquering much of Europe. That seems just rude.

This map is not accurate. I tested by looking at the Maldives, of which the highest point is only 2.4m above the sea level but even at 7m, the map indicates that some islands would be above the surface.

Sea rise is not distributed equally around the globe though.

https://en.wikipedia.org/wiki/Tidal_range

I happen to have visited both extremes (Caribbeans and the Bay of Fundy).

For the Rio de Janeiro region, at least, it seem it is using the top of the buildings as if it were the ground level. That makes for very optimistic forecasts.

I found a bug. According to the map, if sea levels rise by 1 meter then both Death Valley and the Salton Sea will be completely flooded. But if there's a 0 meter sea level rise, they remain unflooded. I guess relying elevation maps does not give the whole story.

"Note: Some inland depressions, such as the Caspian Sea, show inundation on the map but would not be flooded. This is because the mapping algorithm is based upon elevation and can not distinguish areas that are separated from the oceans by a ridge or other high area. Be sure that you trace a connection with the ocean before assuming the area would be flooded. "

Original: http://flood.firetree.net/

Description: http://blog.firetree.net/2006/05/18/more-about-flood-maps/

This map's default setting of a +7 meter rise would be reached in the year 4348 if sea levels continue to rise at the current rate.

(You can get current and historical sea height satellite data from http://sealevel.colorado.edu/)

There are reasons to assume that a linear fit is not smart.

If you assume the rate of melting is roughly proportional to the temperature, then we are in for an increase in rates.

But there are other things. Nonlinear ice effects - that are not very well included in IPCC projections, could cause a lot more sea level rise sooner. They are hard to predict.

http://phys.org/news/2015-09-eyes-oceansjames-hansen-sea.htm...

Because we are talking about such tiny numbers when we are talking about the current sea level rises, anything spectacular in the future has to be non linear in nature or it just would not matter.

It amazed me just how linear historical sea levels have been. Take a look at measured New York sea levels, which have been kept since before the Civil War.

http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.s...

Basically there are a few dangerous ways glaciers can react nonlinearly, raising sea level (from watching a few videos).

Perhaps best is to watch this long presentation by Eric Rignot from NASA JPL a few times, it's very fascinating and also terrifying.

https://www.youtube.com/watch?v=3p9uRxX95f4

Imagine two kilometers of glacier sitting on bedrock that's 500 meters below sea level. The glacier doesn't touch sea water because there's higher ground between it and the sea, though still below sea level, and also that's blocked by ice. If that blocking ice melts, the warm and salty water can then touch the big glacier that then starts melting and calving icebergs. Or if the glacier is on higher ground, it can start directly sliding towards the sea.

There are multiple glaciers in Greenland and Antarctica that each could contribute one meter to sea level rise, that the scientists are watching. Eric Rignot named the parts between the glacier and the sea Flood Gates.

We haven't observed ice sheet collapses, so it's hard to know how it will play out, how long it will take, one or more centuries. We also can't afford to wait and observe them and only then do something about it.

Neat! Here I thought I was sufficiently inland in South Florida. I never even considered that the Everglades would flood me out before the Atlantic did. Heck, my parents house near the beach would fare better than mine near the Everglades, and those lucky dogs would get beachfront property while mine was completely underwater!

I want this but more detailed and for sea level drops. I think due to rising water levels there is a massive amount of underwater archeological finds that havent been properly found simply due to a misunderstanding of where coastlines used to be at in the ancient past.

Relevant: https://what-if.xkcd.com/53/

People who doubt the doubt the accuracy of this map should check their brain. It is only a simulation based on some assumptions, not facts! If you do not satisfy with it, go and find 60M+ of water and pour it in your country.

Are there any predictions for the next X-years of how high the seas might rise?

In its most recent assessment report (2013), the IPCC predicts a sea level rise between 50cm and 1m by the end of the century with the CO2 emissions worst case scenario. In the best case scenario, it would be between 30 and 60 cm.

They are predicted to rise about 80cm up to 2100. If Greenland melts that's another 7.2m but that might take a while.

The currently quoted number in policy papers is around 1 meter in the next 100 years. The includes the assumption that sea level rise is accelerating beyond historical trends.

For fun, you can get sea level rise satellite data for the past 20+ years from http://sealevel.colorado.edu and run your own math. If you just naively run forward the observed rate over the last 22 years, you get 1 meter of rise in 300 years.

You can also see historical tide data for cities here http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.s...

It's important to know that tide data combines sea level information with information on how much the city is sinking. A bedrock city like NYC will give you better data on sea level rise than a city built on mud, like Venice, which is going into the water even if global sea levels were falling instead of rising.

i heard more like 0.55m in the next 100 years

You are correct. That's far more likely, and probably still too high.

The one meter over 100 years figure is the worst case number in the reports. Of course the bigger number gets the most press.

The last one hundred years have had a .10 to .20 meter rise, depending on who you ask.

Nothing to worry about then... I'm still above water and +60m, but the city centre has flooded.

Doesn't look good for the Netherlands...

Well, at least part of the Netherlands (approx. 26%) are already below sea level. And it doesn't look that bad.

Netherlands is protected by dams. The solid geology of the area has allowed for durable dams to be constructed over centuries.

Places like Florida are going to be severely hit by rising sea levels because so much of the land is porous. You can't build a dam to stop the sea if it seeps in from underground.

Just out of interest, how tall are the dams?

The dams in the famous Zuiderzee Works [1] are about 13m high, it seems.

[1] https://en.wikipedia.org/wiki/Zuiderzee_Works

Well, according to this, my house should already be under water. That's what happens when you live below the water level of the neighbouring canal...

Well, given that it predicts half of the Netherlands will be flooded with just a 1m rise in sea level, which happens about twice a day, I'm a bit sceptical.

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