Ice caps melting = water rising?

[pikapika!]

I've heard that if the ice caps melt the oceans will rise.

but i thought that water expands when freezing.

is this a myth?

 

[ukmicky]

It does but the ice they are talking about is sitting on land rather than the sea.

 

[Pythagorean]

I've heard that if the ice caps melt the oceans will rise.

but i thought that water expands when freezing.

is this a myth?

It just won't be proportional to the size of the ice that melts, but it will still contribute to the sea level.

 

[Langbein]

I've heard that if the ice caps melt the oceans will rise.

but i thought that water expands when freezing.

is this a myth?

It's true that most of the melting ice is on top of land, like the ice cap of Greenland.

But then for the floating ice:

Take a glass of water and put an ice cube into it. Wait until it melts. Which way did the surphase of the water in the glass move, up or down?

Where will the expanded part of the wather when freasing to ice normally be located, for a floating ice cube ?

 

[cristo]

Take a glass of water and put an ice cube into it. Wait until it melts. Which way did the surphase of the water in the glass move, up or down?

Neither.. the water level remains the same.

 

[DaveC426913]

The density of floating ice vs. water has no effect on water level. See diagram.

 

[Langbein]

The density of floating ice vs. water has no effect on water level. See diagram.

Yes, you are right. I should not speak about experiments without performing them. The volume above the surphase should be exactly the same as the expansion volume so there should be no change at all - right ?!

Shame, stupid me ..

 

[billiards]

In the short term we shouldn't be too worried about ice bergs and ice shelves melting, because they are floating so when they melt they do not contribute to sea level rise. It is grounded ice that melts that will contribute to sea level rise, the largest ice caps on Earth are grounded (e.g. Greenland, Anterctica).

Q/What is the single largest contributor to sea level rise?

A/Thermal expansion. Because when you heat water up it becomes less dense (i.e. its volume increases), and because water is a fluid, it will spread its volume evenly over the entire ocean (ignoring self-gravitational effects).

 

[Pythagorean]

Neither.. the water level remains the same.

I think he's referring to ice on land, as from the North and South (an) arctic.

 

[Plastic Photon]

Take a glass of water and put an ice cube into it. Wait until it melts. Which way did the surphase of the water in the glass move, up or down?

True, but would you say this is an appropriate analogy, to compare the Earth's oceans to a cup of water?

 

[Evo]

True, but would you say this is an appropriate analogy, to compare the Earth's oceans to a cup of water?

Ice melt from ice over water will not increase sea level, only ice melt from ice over land will have an impact and it will not be uniform, there will be variations with rises in some areas, while other areas could see a fall.

 

[Ivan Seeking]

The main concerns are the melting ice in Greenland and the Antarctic. Expansion of the water from heating is also a factor.

Evo, I was not aware of any predictions that water levels could fall in some areas. Where does this come from?

 

[Evo]

Evo, I was not aware of any predictions that water levels could fall in some areas. Where does this come from?

From the IPCC, from the EPA...

According to the IPCC, current model projections indicate substantial variability in future sea level rise between different locations. Some locations could experience sea level rise higher than the global average projections, while others could have a fall in sea level.

http://www.epa.gov/climatechange/effects/coastal/index.html

 

[billiards]

The most likely cause I can think of for the variability would be uplift and subsidence of the crust. E.g. SE England's coast will become submerged even if global sea levels do not change, the land is subsiding as mantle material diverges towards the north of Britain which is currently undergoing isostatic rebound in response to the melting of the ice cover at the end of the last glacial maximum.

 

[Andre]

Meanwhile Hudson Bay and the Baltic sea are on it's way to become land.

 

[Plastic Photon]

A rapid melt in arctic ice with an inhibited flow into the Atlantic could submerge islands in the arctic. The situation depends on whether the melting of ice is uniform or a sudden gush. I have to believe that either way, the melting of the artic ice cannot be felt uniformly throughout the world's oceans. If say for some reason, a large iceberg cuts off the Berring, and the arctic ice melts, there may be a chance the coastal regions of the Atlantic in England, North America and Europe could suddenly sea a sharp rise in ocean levels.

 

[billiards]

It would have to be a very rapid melting for the effects to be felt locally at the scale that you are discussing, and besides even if there were a great flood, it would soon disperse.

 

[DaveC426913]

If say for some reason, a large iceberg cuts off the Berring, and the arctic ice melts...

How would a floating iceberg cut off water flow? The water flows under it.

 

[Plastic Photon]

How would a floating iceberg cut off water flow? The water flows under it.

Think of an iceberg not as a surficial chunk of ice but as massive structure which remains largely submerged. If icebergs floa, in terms of mass, on the surface, the Titanic would not have sunk.

Has anyone considered the change in salinity of the ocean water as a major factor in ocean rise with ice cap melt in the arctic?

 

[bigdrum]

I have been looking at this type stuff all over the world. And if you look very closely at land terrain on google earth, you will notice tons of villages and cities are built in a valley or an old river bed. So when the caps do melt, obviously the water will increase. Some people say between 20 to 200 feet the levels will increase.

Whatever it may be, I only hear them (the media) speaking about the sea level.
We all know how the media omits what they want to and what the government wants them to. So won't a lot of the river systems be affected as well? I would think so.

And I'm wondering if anyone has drew up some pictures using these predictions of Earth's future. The signs are already there that the water has been been there, so why not fill in the dots and see what Earth looks like with a complete meltdown so we can begin preparing to move to higher ground.

 

[Moonbear]

A fairly recent article in Science addresses the challenges in determining what the net effect of global warming will be on the ice caps.

Measurements of Time-Variable Gravity Show Mass Loss in Antarctica
Velicogna and Wahr
Science 24 March 2006: 1754-1756

Here are some excerpts:

The Antarctic ice sheet is Earth's largest reservoir of fresh water. Accurate estimates of its mass variability, accompanied by realistic error bars, would greatly reduce current uncertainties in projected sea-level change, with obvious societal and economic impacts. There have been substantial improvements in monitoring the ice sheet in the past few years (1–3), although recent studies have provided contrasting mass balance estimates (1, 3).

Antarctic mass variability is difficult to measure because of the ice sheet's size and complexity. Previous estimates have used a variety of techniques (1), each with intrinsic limitations and uncertainties. A problem common to all these techniques is the difficulty of monitoring the entire ice sheet. Studies that rely on a single method can provide estimates for only a portion of the ice sheet, and even studies that synthesize results from several techniques suffer from sparse data in critical regions.

The most recent Intergovernmental Panel on Climate Change (IPCC) assessment estimated that the Antarctic contribution to sea-level rise during the past century was 0.2 ± 0.3 mm/year (2). The report predicted that the Antarctic ice sheet will probably gain mass during the 21st century because of increased precipitation in a warming global climate. Recent radar altimeter measurements (3) have shown an increase in the overall thickness of the East Antarctic Ice Sheet's (EAIS's) interior during 1992–2003. However, the IPCC prediction does not consider possible dynamic changes in coastal regions, and radar altimetry provides only sparse coverage of those areas (2). Detailed interferometric synthetic-aperture radar and airborne laser altimeter surveys of glaciers along the edge of the West Antarctic Ice Sheet (WAIS) show rapid increases in near-coastal discharge during the past few years (4). The overall contribution of the Antarctic ice sheet to global sea-level change thus depends on the balance between mass changes in the interior and those in coastal areas (1). The gravitational survey of Antarctica provided by the Gravity Recovery and Climate Experiment (GRACE) satellites and discussed in this paper is a comprehensive survey of the entire ice sheet and is thus able to overcome the issue of limited sampling.

Before interpreting the scaled results as ice sheet change, we had to address the issues of errors in the GRACE gravity fields and the contamination from other geophysical sources of gravity-field variability.

By fitting a trend and annual and semiannual terms to the WAIS and EAIS results, we find that most of the Antarctic mass loss comes from WAIS. After correcting for the hydrology leakage and the PGR signal, we obtain a WAIS mass loss of 148 ± 21 km3/year. The EAIS mass loss is 0 ± 56 km3/year. Because of its relatively large uncertainty, we are not able to determine whether EAIS is in balance or not.

http://www.sciencemag.org/cgi/content/full/311/5768/1754