# If the polar ice cap is melting... **URL:** \ **Category:** Factual Questions\ **Created:** [September 30, 2006, 5:04pm UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749 "2006-09-30T17:04:38Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 1, 2006, 11:06pm UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/21 "2006-10-01T23:06:54Z")
[QUOTE=Peter Morris] erm, very interesting, guys, but totally irrelevent. The fact is that water DOES float. Speculating about what would happen if it didn’t is a futile excercise, with no right answers. Besides, it’s not what the OP was asking about. [/QUOTE] What does that have to do with anything? GQ threads can take on a life of their own. 🙂 ---
**Author:** ![Hilarity\_N.Suze](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hilarity_n.suze/32/6223_2.png) [@Hilarity\_N.Suze](https://boards.straightdope.com/u/Hilarity_N.Suze)\ **Post date:** [October 1, 2006, 11:14pm UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/22 "2006-10-01T23:14:14Z")
Cold water is less dense, okay, so it goes to the top. But when water warms it expands and takes up more room. This sounds like a contradiction. Sorry–I don’t know a lot about this stuff–but it does to me. If it’s less dense it takes up more room, and if it expands it takes up more room. Right? ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [October 2, 2006, 12:53am UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/23 "2006-10-02T00:53:29Z")
[QUOTE=Hilarity N. Suze] Cold water is less dense, okay, so it goes to the top. But when water warms it expands and takes up more room. This sounds like a contradiction. Sorry–I don’t know a lot about this stuff–but it does to me. If it’s less dense it takes up more room, and if it expands it takes up more room. Right? [/QUOTE] It’s an anomaly. Most things contract and the density increases as they are cooled right through the freezing point and beyond. Water is anomalous. If you cool water it contracts and its density increases down to about 4 C (39.2 F). Then it starts to expand and its density decreases up to the maximum in this temperature region at about 0 C (32 F). This is why ice floats. All of this is at standard atmospheric pressure, like on the surface of a lake. The freezing point is remarkably stable to a pressure of about 500 atmospheres which corresponds to an ocean depth of a little over 16000 ft. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [October 2, 2006, 12:56am UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/24 "2006-10-02T00:56:54Z")
[QUOTE=David Simmons] It’s an anomaly. Most things contract and the density increases as they are cooled right through the freezing point and beyond. Water is anomalous. If you cool water it contracts and its density increases down to about 4 C (39.2 F). Then it starts to expand and its density decreases\*\* up to the maximum\*\* in this temperature region at about 0 C (32 F). This is why ice floats. All of this is at standard atmospheric pressure, like on the surface of a lake. The freezing point is remarkably stable to a pressure of about 500 atmospheres which corresponds to an ocean depth of a little over 16000 ft. [/QUOTE] Make the bold part read **down to the minumum**. See how easy it is to screw up? The **up to the maximum** thing would apply to the amount of expansion. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 2, 2006, 2:30am UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/25 "2006-10-02T02:30:07Z")
[QUOTE=Hilarity N. Suze] Cold water is less dense, okay, so it goes to the top. But when water warms it expands and takes up more room. This sounds like a contradiction. Sorry–I don’t know a lot about this stuff–but it does to me. If it’s less dense it takes up more room, and if it expands it takes up more room. Right? [/QUOTE] The anomaly is due to hydrogen bonding between water molecules. Below 4 C the molecules begin to arrange themselves in hexagonal formations that take up more space than liquid water. It is this factor that makes water expand as it cools below 4 C, and results in ice being less dense than liquid water. In water above 4 C the water molecules become farther apart as the water warms, like most substances. In water below 4 C the water molecules become farther apart as the water cools because of the formation of special bonds between the molecules that hold them apart. A small number of other substances also expand when they freeze; these include , gallium, bismuth, acetic acid, antimony and silicon. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [October 2, 2006, 2:44pm UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/26 "2006-10-02T14:44:20Z")
[QUOTE=David Simmons] … The OP poster then followed up with a question… [/QUOTE] Ah, I didn’t notice that it was the same person. Carry on, then. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [October 2, 2006, 3:58pm UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/27 "2006-10-02T15:58:59Z")
Calling **Hilarity N. Suze** , calling **Hilarity N. Suze** Was you question answered satisfactorily or are you more confused than ever? Inquiring minds want to know. If the answers weren’t satisfactory don’t just go away muttering about “these scintists.” Come back and bitch and say “I didn’t understand a word you wrote” or if clarification is needed ask for it or say “OK, I got it now.” If you asked the question you must have wanted an answer. Did you get one? ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [October 2, 2006, 4:53pm UTC](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749/28 "2006-10-02T16:53:18Z")
[QUOTE=grant16] then are sea levels also rapidly rising? [/QUOTE] Define “rapidly” From this post by myself: [http://boards.straightdope.com/sdmb/showthread.php?p=7753550#post7753550](http://boards.straightdope.com/sdmb/showthread.php?p=7753550#post7753550) \*The current rate appears to be almost 2mm a year, or 15 or so years to raise the sea level one single inch. [http://www.sciencedaily.com/release...51124220656.htm](http://www.sciencedaily.com/release...51124220656.htm) That rate is disputed and unclear: [http://md1.csa.com/partners/viewrec...2&setcookie=yes](http://md1.csa.com/partners/viewrec...2&setcookie=yes) Global mean sea level is a potentially sensitive indicator of climate change. Global warming will contribute to worldwide sea-level rise (SLR) from thermal expansion of ocean water, melting of mountain glaciers and polar ice sheets. A number of studies, mostly using tide-gauge data from the Permanent Service for Mean Sea Level, Bidston Observatory, England, have obtained rates of global SLR within the last 100 years that range between 0.3 and 3mm/yr, with most values concentrated between 1 and 2 mm/yr. However, the reliability of these results has been questioned because of problems with data quality and physical processes that introduce a high level of spatial and temporal variability. Sources of uncertainty in the sea-level data include variations in winds, ocean currents, river runoff, vertical earth movements, and geographically uneven distribution of long-term records. Crustal motions introduce a major source of error. … … Furthermore, not all climate models are in agreement. Opposite conclusions may be drawn from the results of other GCMs. In addition, the West Antarctic Ice Sheet is potentially subject to dynamic and volcanic instabilities that are difficult to predict. Because of the great uncertainty in SLR projections, careful monitoring of future sea-level trends by upgraded tide-gauge networks and satellite geodesy will become essential. Finally, because of the high spatial variability in crustal subsidence rates, wave climates and tidal regimes, it will be the set of local conditions (especially the relative sea-level rise), rather than a single global mean sea-level trend, that will determine each locality’s vulnerability to future SLR. " So, if the rate is 0.3mm/year, it’d take nearly 100 years to raise one inch. At the highest current estimate, it’d take 8 years to increase one inch.\* [Previous page](https://boards.straightdope.com/t/if-the-polar-ice-cap-is-melting/374749.md?page=1)