Thread: Rising sea levels? Basic physics?

Can someone please explain how the sea levels will rise so dramatically if the ice caps melt?
Looking at this in laymans terms. The ice has a volume (obviously). If one puts an ice cube into a glass of water, the water will rise by the volume of the ice (again obvious). But if you take out the ice, the water will fall. But if you put the melted volume of the ice (i.e. water) back into the glass you will get roughly the same level of water again...?
Is it not the same for Global Warming?
I feel that most statistics are based on the volume of water comprising the ice caps and if they were to be added onto the sea levels already without factoring in their effect on the current sea levels...etc.

Any comments?

Barry

The ice which is of concern is the ice that is grounded on land in Antarctica and Greenland. If and when this melts it will lead directly to an absolute rise in sea level.

Yes that's what I thought, I didn't account for the land based material.
Surprisingly the media seem to focus more on the water based ice and dramatic pictures of it falling into the water...etc.

Very interesting nonetheless and thank you for the reply.

Barry

Originally Posted by Barry Flannery

Surprisingly the media seem to focus more on the water based ice and dramatic pictures of it falling into the water...etc.

the media have always been a sucker for the pretty picture

however, the shrinkage of the arctic ice, even though it won't cause a noticeable rise in sea levels, could be indicative of the shape of things to come :

1) lower albedo could cause a positive feedback loop
2) the shrinkage happens faster than models predict, indicating that if anything the current models err on the side of caution

or put another way, arctic ice is the miner's canary of global warming

Originally Posted by Barry Flannery

Surprisingly the media seem to focus more on the water based ice and dramatic pictures of it falling into the water...etc.

Thos pictures are of land based ice entering the sea. It will have an effect if the rate of infall exceeds the amount of fresh snow falling inland.

Originally Posted by Barry Flannery

Can someone please explain how the sea levels will rise so dramatically if the ice caps melt?
Looking at this in laymans terms. The ice has a volume (obviously). If one puts an ice cube into a glass of water, the water will rise by the volume of the ice (again obvious). But if you take out the ice, the water will fall. But if you put the melted volume of the ice (i.e. water) back into the glass you will get roughly the same level of water again...?
Is it not the same for Global Warming?
I feel that most statistics are based on the volume of water comprising the ice caps and if they were to be added onto the sea levels already without factoring in their effect on the current sea levels...etc.

Any comments?

Barry

You are correct to be puzzled. I'm a geologist and even I don't get it. There are many variables that determine sea levels and use caution against simple 'one on one' predictions. There is some scientific evidence of global warming although not all agree on the extent, cause, etc. This is a far cry from any good science on the 'consequences' of global warming....this enters into the realm of educated speculation. One's acceptance or not of particular consequences is more tied to agenda than science....everything from 'ho hum' to the 'sky is falling'. Just be cautious of the opinions of those who claim to juggle a thousand variables in their head and 'know' the answer (but couldn't draw you a carbon based molecule what the science debate revolves around and explain it's properties :wink: ).

Next time someone quotes a figure ask them a question like 'do you mean parts per billion or parts per trillion' and they won't have a friggin clue despite that one answer or the other makes the carbon value a thousand times larger or smaller....Or 'ask 'do you actually mean a rise centimeters and not milimeters, I read it was millimeters'. If they answer with 'I'm not sure,yu could be right but I thought centimeters' then you know they don't have a friggin clue what they are talking about as there would be no uncertaintly if the rise was 10 times greater or ten times less. Folks quote 'facts' on both sides of the global warming debate like mindless groupies in a cult.