54
Water is a rather strange substance. With most substances, the solid phase is denser than is the liquid phase. This is not the case with water. Ice is less dense than liquid water. A side effect of this effect is that liquid water very close the the freezing point is less dense than is slightly warmer water. That very cool water sinks.
Liquid fresh water ...
53
Water melts at 0 °C (32 °F) but freezing is a more complicated affair. It is safe to say water gains the ability to freeze at 0 °C, but it can get much cooler before it actually does so resulting in supercooled water. Water in this state can rapidly solidify when suitable ice nuclei are introduced. For example, in convective clouds, liquid water can be ...
45
There are two ways this problem needs to be looked at. The first is more astronomy than Earth science. The Earth as an entire system is largely contained. Its gravity and magnetic field retains nearly all of its elements. Earth does lose hydrogen and helium and cosmic rays will split water molecules leading to a loss of an impressive amount of ...
38
Water has lowest EM absorption in the blue part of light spectrum and increases rapidly towards both UV and red parts of spectrum.
As a result in visible light water is blue. Same goes for the ice as it has very similar absorption spectrum.
While there is a lot of white in the picture, all of it is a thin snow cover on top of blue ice. Once the snow ...
37
When dissolved in water, salt breaks up into sodium and chlorine ions, which combine with water molecules so they cannot easily sink. However, there is a tendency for streams of fresh water to float on salt water and rise to the top. This caused problems for British submarines in the Dardanelles Straits during WW1. Moving from almost fresh water to the ...
33
What does it take to reduce the salinity?
The salinity of sea water is around 35 g/kg. There are around 1,350,000,000 km³ of water, so roughly 1.3x1021 kg of seawater (1 kg/l, which is a bit off for saltwater of course, probably by 35 g). Which contains about 4.7x1019 kg of salt.
To reduce the salinity to just 34 g/kg, you need to extract 1.4x1018 kg of salt ...
29
Just to add some further discussion to @Pont and @fre0n excellent answers.
The problem of the water needed to submerge the world during the Genesis flood have been discussed for centuries. The narrative could seem legit as traces of marine condition can be seen even in high mountains. The Biblical flood was the most logic explanation for marine fossils ...
28
How can we still lack groundwater?
That 71% of the Earth's surface is covered by oceans is completely irrelevant to the issue of fresh groundwater depletion. Salty groundwater is useless for drinking or irrigating crops.
The issue at hand is the depletion of those underground reserves of fresh water. This depletion can result from natural or human causes. ...
28
Why does the salt in the oceans not sink to the bottom?
Because there isn't any "salt", per se, in the ocean. Salt, as the compound sodium chloride (NaCl) does not exist as a solid in the ocean. It is dissolved into sodium and chloride ions (charged atoms) that exist within the ocean as a homogenous phase (that is, a "thing").
That said, water with sodium ...
25
Why doesn't 71% water of the earth dry or evaporate?
The simple answer: Because it rains.
The not so simple answer: By some estimates, the Earth has already lost about a quarter of its water, and it is predicted to lose almost all of its water in a billion or so years from now.
It rains because temperature decreases with altitude. This lapse rate means ...
24
I am interpreting your question as referring to rivers with flowing water freezing as as opposed to glaciers, which are already frozen.
Under current climatic conditions, small rivers can freeze throughout: from bank to bank, surface to river bed. I'm avoiding using the word solid as some people use that word when a river's surface has frozen from bank to ...
23
there is not enough existing water inside this geosystem IMO for such a thing to occur. Let's see these figures here:
One estimate of global water distribution
Oceans, Seas, & Bays 1,338,000,000 -- 96.54% of all water
this figure means that most of the existing water at the global scale is seawater. Sea floor is quite irregular, with some abyss like ...
21
In water wave physics, when we say that the wave "feels" the bottom, we mean that the water depth affects the properties of the wave.
The dispersion relationship for water waves is:
$$
\omega^2 = gk \tanh{(kd)}
$$
where $\omega$ is the wave frequency, $k$ is the wavenumber, $d$ is the mean water depth, and $g$ is gravitational acceleration. We ...
21
Due to convection (the cold water sinks while the warm water rises), the entire pond needs to be brought to near-freezing temperatures before the surface can freeze. With only the top of the pond in contact with the cold air, this takes a long time.
Additionally, the ground (which is not cooled by convection) will take even longer to cool down, ...
20
The "precipitation rate" part is easy to answer, at least to a first approximation. We have 40 days and nights (960 hours) in which to raise sea level above the peak of Mount Everest (let's round up and call it 9000m). Thus, we need a precipitation rate of around 9000/960 =~ 9.4 metres per hour. For comparison, the largest rainfall ever recorded over an hour ...
19
The residue dry powder you refer to is salt.
Salt is toxic to most plants. The United Nations claims the world is already losing 2000 hectares per day of farm land to salt-induced degradation. This is land that is used to feed people.
In some situations, salt from affected lands can contaminate underground sources of drinking water, which will affect people, ...
17
Feel the bottom refers to the fact that the wave-induced velocity field extends all the way from the top of the water column to the bottom of the water column. When the wave "feels the bottom" it means that there is some interaction with the bottom boundary. A very thin boundary layer develops at the bottom where vorticity is generated due to the velocity ...
16
This is a really complex problem and would require a really detailed explanation about atmospheric circulation, meteorology and hydrology.
The short answer to your question is that water is going somewhere else. If you look at the studies about moisture recycling, among the others van der Ent et al 2014 or 2010, you can see that the precipitation that ...
16
"Transparent" is not the same as "white" : white bodies reflect most of the light while transparent bodies let the light though. Once the light enters into water, it may need to travel a long way before it has a chance to go out, and that long travel path provides more opportunities for absorption.
Water absorbs light by itself much more than snow, but ...
14
In my opinion, there is no such thing as water veins as described in this article, but, it is a fact that there is water circulation underground.
In the natural environment, water can either circulate in porous mediums (like within the small spaces between sand grains in sandy soils) or as underground streams. There is also the concept of the water table ...
14
The water in a pond is in contact with the ground and the ground is not even close to freezing even if the air temperature is 27° below freezing.
14
You're making a mistake, at least for the second case:
In the second case, the water ends up as rain, presumably within a few hundred kilometers of the evaporation point.
You cannot model a dry region (or indeed any region on earth) as a closed system for hydrological purposes. When water evaporates in a dry climate, it transports much farther than a ...
13
This is an interesting question & I've been waiting to see what answers, if any, would be written.
One affect of creating such a lake would be a localized increase in humidity in the vicinity of the new lake, but nothing that would significantly increase rainfall.
By bringing in salty sea water there could be a risk of contaminating existing ...
12
Yes, it is real. Whoever took the photo, congratulations on a very fine image.
I have never seen this texture on such a scale, but something similar can be achieved in the laboratory by creating a bubble membrane of pure super-cooled water and blowing a few dust nuclei onto the surface. A comparable geometry appears very rapidly. The size of the ice crystals ...
12
If water on Earth came from meteorites, why doesn't Mars have substantial water?
First off, that's a conjecture regarding the origin of the Earth's water rather than a known fact. A few times a year or so, a new journal article will appear that argues that the Earth's water is primordial, then another arguing that it came from comets, then yet another ...
11
What I miss in the other answers is water quality.
Even is there is sufficient water available it is often of insufficient quality for the purpose you want it for:
We often don't drink straight out of rivers
We don't irrigate with salt water
etc.
So you need to spend effort to prepare it for use. This adds to the experience of shortage.
11
I'm a regular from the Physics Stack Exchange reporting for duty.
Why this is a serious question
This is a bigger question than you might be giving it credit for. The question is ultimately similar to asking why all the air molecules in the atmosphere do not fall to the floor. Your question comes from a very solid principle in physics which could be called ...
10
The average ecological footprint of a US citizen has been estimated as 8.00 global ha.
Multiplying 8.5 million by 8.00 hectare gives 680,000 km², or around 5 times the area of New York state.
Of course, this calculation contains a lot of assumptions and simplifications. This doesn't mean you could simply allocate 680,000 km² around New York City and use ...
10
In a way, glaciers are just like frozen rivers. A good start on that topic comes from USGS. Ice (whether in a frozen river or in a glacier) is still a fluid and thus is always moving because of its own weight. A frozen river will still be a river of incredibly slow moving water.
When water is not moving, first the entire volume cools down to 4C (maximum ...
10
Leaves, mostly. Photosynthesis requires carbon dioxide, and it gets it via stomata - small controllable pores in the leaf. When the stomata open, water goes out, because the air is generally drier than the interior of the leaf. Water in the leaves is drawn up from the roots, via the xylem, using the suction from the lost water in the leaves, and also acting ...
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