70 Metre Rise In Sea Level?

[stilicho]

I don't see why the rate of melting should increase exponentially. Also, "one metre in twenty years" is a pretty extreme forecast - a metre this century is more mainstream. A seventy metre rise would take many centuries, if not thousands of years. We could maybe lose most of Greenland's ice in a few hundred (most of Greenland is below sea-level so once the ocean breaks in things will really get moving) but it's physically difficult to get all that ice off East Antarctica - it all has to come off one side because of the Antarctic mountain range on the other.

I thought it might increase exponentially just because natural systems appear to behave that way.

I am concerned, of course, about the loss of agricultural land and areas such as The Netherlands. But isn't adaptation to this scenario plausible?

I am interested in why you think the ice cap melting wouldn't be exponential. I tried it in a glass of water and heat does seem to reduce the size of the ice cubes faster until they are all gone.

 

[stilicho]

What do you mean by "breaks in"? As I understand it, Greenland is dished due to the weight of ice, with the centre the furthest below sea-level. It would take a lot for the ice to get into the sea, and if it melted in situ a huge lake would form.

Is that true? I thought the mass of the ice was what kept the land masses down. Is there an example of a land mass that stayed down once the ice was removed?

 

[CapelDodger]

What do you mean by "breaks in"? As I understand it, Greenland is dished due to the weight of ice, with the centre the furthest below sea-level. It would take a lot for the ice to get into the sea, and if it melted in situ a huge lake would form.

Greenland is bowl-shaped, with (as I understand it) some low points around the rim. If sea-level rises enough to push ocean water through the low-points it will speed up the ice-loss considerably. I don't think we'll be seeing that anytime soon, though.

 

[CapelDodger]

I thought it might increase exponentially just because natural systems appear to behave that way.

I am concerned, of course, about the loss of agricultural land and areas such as The Netherlands. But isn't adaptation to this scenario plausible?

I am interested in why you think the ice cap melting wouldn't be exponential. I tried it in a glass of water and heat does seem to reduce the size of the ice cubes faster until they are all gone.

If you keep the ice-cube above the melt-water (say, balanced on a bottle-cap or some such) you'll see that it melts much more slowly. Ice absorbs heat from water much more readily than from air. (If you build an ice-house the first thing you need to ensure is good drainage.)

The ice on Greenland and Antarctica is not in contact with water (except at the margins, of course). It can only gain energy from radiation and from contact with the atmosphere. If ocean-water gets under the Greenland ice that will change, of course, but that can't happen on Antarctica. A full melt of Greenland would be about seven metres, as I recall, so Antarctica holds ~ 90% of the total ice.

As to adaptation, tell that to the Dutch . A few metres and they're gone, and it's much the same for Denmark. East Anglia would be an archipelago. (Fortunately my mother and my sister's family live at one of the highest points of Suffolk, two of my nephews are into sailing, and my brother-in-law's a civil engineer so the future looks reasonably bright for them.)

 

[CapelDodger]

Is that true? I thought the mass of the ice was what kept the land masses down. Is there an example of a land mass that stayed down once the ice was removed?

The land mass will rise, but very slowly. It involves plastic deformation of the underlying rock, which will flow back under the previously depressed land. In the UK that means that Scotland is gradually rising while the South-East is sinking (as the underlying rock flows northward). The floor of the Baltic is also rising, as can be seen from beach-lines and one-time ports that are now quite far inland.

The ice-caps have been gone for ten thousand years, so as you can see the process is very slow.

 

[luchog]

hrm... looking at the map for the Seattle area, our steep, mountainous terrain means that very little will actually be affected. Seattle proper wouldn't lose more than a a bit of the waterfront and a few downtown streets.

Farther south, huge swaths of Kent and Renton would be flooded out, as would large sections of Georgetown/South Park, as well as Fremont on the north end. Many would argue that this is not necessarily a bad thing. (True Seattle natives never pass up a chance for a good Renton joke.)

 

[BenBurch]

hrm... looking at the map for the Seattle area, our steep, mountainous terrain means that very little will actually be affected. Seattle proper wouldn't lose more than a a bit of the waterfront and a few downtown streets.

Farther south, huge swaths of Kent and Renton would be flooded out, as would large sections of Georgetown/South Park, as well as Fremont on the north end. Many would argue that this is not necessarily a bad thing. (True Seattle natives never pass up a chance for a good Renton joke.)

As long as you lose Federal Way, too, you can consider it a benefit.

 

[CapelDodger]

Farther south, huge swaths of Kent and Renton would be flooded out, as would large sections of Georgetown/South Park, as well as Fremont on the north end. Many would argue that this is not necessarily a bad thing. (True Seattle natives never pass up a chance for a good Renton joke.)

True Londoners never pass up a Kent joke (lots of that will go), and as for Essex, well, only comedians will miss it.

Things don't look too clever for Cardiff in the long term, though, unless Torchwood can come up with something.

 

[rjh01]

At least Australia will be safe from floods. That is occurring to the link provided. Mind you I think Australia may suffer badly from lack of rainfall due to climate warming.

 

[stilicho]

As long as you lose Federal Way, too, you can consider it a benefit.

Is that sort of like Wetaskiwin's "Auto Mile"?

http://www.pbase.com/poundstone/image/68851273

Capeldodger: I admit my "experiment" has its drawbacks. But is the rate of sea ice loss increasing now while the rate of ice cap loss is steady? And does the sea ice loss have a bearing on sea levels?

 

[macdoc]

Sea ice loss has no bearing on sea levels.

Only net glacial mass loss does. ( and tundra melt )

For Greenland it's been as high as 220 cu km in 2005 and varies a bit year to year.

Globally it's maybe 3 x that.

There is a bit too much concentration on near term sea level rise but it's canary as once set in motion - positive feedbacks make complete melt just about inevitable and we can never mitigate that - the energies are too great as we are seeing with the Arctic cover drop.

Many feel Greenland IS gone but still any complete melt is millenia away unless we get into the 6 degrees C global rise then the sea level rise is the least of our concerns.

 

[TrueSceptic]

Is that true? I thought the mass of the ice was what kept the land masses down. Is there an example of a land mass that stayed down once the ice was removed?

Yes, but how quickly does isostatic rebound take place? And if the ice stays where it is, melted or not, the weight is not being removed, is it?

 

[TrueSceptic]

Greenland is bowl-shaped, with (as I understand it) some low points around the rim. If sea-level rises enough to push ocean water through the low-points it will speed up the ice-loss considerably. I don't think we'll be seeing that anytime soon, though.

I can't see that happening either.

 

[macdoc]

The greater risk to ocean infiltration is in the western Antarctic.

http://en.wikipedia.org/wiki/West_Antarctic_Ice_Sheet

 

[Damien Evans]

I wonder: is there another country with a higher %age of its population living on the coast, i.e. with x miles of the sea (where x is, say 5 or 10 miles)?

At least they have plenty of land to move into.

Most of which is also very low lying.

We'd be running to the dividing range.

 

[TrueSceptic]

Most of which is also very low lying.

We'd be running to the dividing range.

+14 m makes little difference. Is there a way of seeing the effects of higher rises?

 

[BenBurch]

Is that sort of like Wetaskiwin's "Auto Mile"?

Except with massage parlors, streetwalkers, and a plentiful crack supply... Unless its gotten better in the last decade...

 

[Damien Evans]

+14 m makes little difference. Is there a way of seeing the effects of higher rises?

Little difference? There'd be well over 2 million displaced from Melbourne alone.

 

[Megalodon]

+14 m makes little difference. Is there a way of seeing the effects of higher rises?

Depends what you mean by little... +1 would flood a number of cities only in North Germany.

 

[TrueSceptic]

Most of which is also very low lying.

We'd be running to the dividing range.

Little difference? There'd be well over 2 million displaced from Melbourne alone.

That was in response to the above, which is about land to move into, not the population affected.