Deep Ocean Water Probelm

[Benjitodd7]

To me there appears to be a paradox with deep ocean water. The deeper you go the colder it gets due to deminishing sunlight levels (relatively quickly the intensity becomes zero). I imagine the temperature gradually decreases nearer and nearer to zero (more precisely the melting point of salt water but lets call it zero) but what stops the water forming ice (that would then probably rise and melt before surfacing)? With ice being less dense, is there a point when very near zero degree water becomes less dense than typical water and actually starts rising? A weird sort of cold water rising convention current? Also doesn't the pressure increase of the water promote formation of ice at higher temperature or does internall friction keep things down there warmer than expected? I guess what I try to get at is doesn't deep ocean water actually increase in temperature after some depth due to cold rising or internal friction or both??? It seems to me that there must be a more interesting processes going on down there than you'd expect. Am just thinking about rubbish too much???

[Benjitodd7]

I never knew the density was maximum at 4degree so thanks for that (this said non sarcastically, and so was that...). Giving this insight I looked into graphs of water density vs temperature and discovered that saline doesn't adhear to this maximum density. This is due to the salt interfering with the formation of hydrogen bonds. Denisty increases as temperature decreases. So maybe the answer to my question is more boring and water just very gradually nears the melting point of saline from above. Looking at salinity vs depth graphs, the salinity of the water doesn't decrease to zero but I'd imagine somewhere like the artic/anit-artic are more or less fresh water??? Does the salt stay in the ice when saline freezes???

[heathfield]

Sea water and fresh water can both exist as liquids below their normal freezing temperature. This occurs when they are subjected to high pressure, and they are in what is called a 'supercooled' state. Such pressures are found in ocean depths, and even under glaciers. Salt water freezes, and retains the salt. The first mapping of northern Greenland was undertaken by an RN team in the 1920s. They moved fast, and determined the land edge by digging down and tasting the ice for salt. Only a few years ago, the US, doubting the accuracy of the RN results, carried out another survey. They were amazed to find just how accurate the RN had been!

[lord molly]

water, when in a solid form will expand. so, with the immense pressure above, the water is being crushed, and there fore cand freexe, as it would need to expand to do so.