Hot answers tagged

52

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 ...


50

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 ...


26

If there is enough water underground, in a sealed reservoir (like under the concrete in the picture), as that water freezes, it will expand, putting pressure on what ever water is left unfrozen. That water will be squeezed out through what ever cracks it can find - in this case, upwards. Because the water is already near-freezing (perhaps even slightly below,...


20

The short answer is: BECAUSE THE ICE IS BLUE. Now we have to explain why it seems perfectly transparent on ice cubes and industrial ice blocks. It has to do with the fact that most transparent materials are not perfectly transparent, and instead absorb (and/or scatter) part of the light that hits them. And when the transparency is better for one specific ...


19

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, ...


17

Indeed some glaciers are growing and gaining mass due to increased precipitation (in part due to climate change and enhanced atmospheric water content). But that's the case only for glaciers in very cold places, like East Antarctica, where most glaciers appear to be growing at increasing rates (1,2). But unfortunately West Antarctica is pretty much a desert; ...


13

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.


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

This is needle ice which forms when moist soil freezes, for example during a cold night. Freezing starts at the ground surface and as ice is formed moisture gradients develop which draws water to the freezing front and growth continues. Ideal conditions may be a sub-freezing night after a rainy day or a sub-freezing night after a day of snow melt. According ...


11

This is a non-trivial issue. When you look at volume change of a glacier, you typically subtract two digital elevation models to obtain the difference between the two. First, you must differentiate between ice sheets where ice berg calving reduces volume and more ordinary glaciers with melt processes. There are of course calving glaciers as well so it is ...


11

Ice can grow up from the ground in the form of needle ice. The formation requires sufficient moisture in the ground. According to the National Snow and Ice Data Center (NSIDC) site needle ice can grow up to 40 cm in length. Needle ice are thin crystals of ice and has a very distinct look. A search on Needle Ice provides a wealth of examples of needle ice, ...


10

It doesn't stay frozen. Ice evaporates (or sublimates is the correct term) under direct sunlight, but that's at a molecular level, it doesn't melt, it goes from solid to gas under sunlight and in the cold, some of this newly formed water vapor goes back being to ice. In an absolutely dry climate, well below freezing, ice would slowly sublimate and ...


9

This picture was taken in what seem to be a small pond, of very calm water. It seem that in ideal conditions, implying but not limited to : absence of winds clean water eg: no nuclei to provide an anchor for crystal formation low temperature gradient between air and watrer (air almost near 0 °C and very slowly falling) ice grain can grow quite large. This ...


9

Is an iceberg the size of Delaware [6,451 square kilometers] actually remarkable, or something that just happens from time-to-time? In March 2000 iceberg B-15 formed which was 11,000 sq. km. and 295 km long. In October 1998 iceberg A-38 formed which was 6,900 sq. km. A Delaware size iceberg would be the 3rd largest in the past 20 years. The 1990 ...


8

This could be because the air cools and heats faster than water. Air has a lower Specific Heat than water. It may take some time for the water to freeze.


8

This phenomenon goes by a number of names: ice heave, ice shove, ice creep, ice tsunami, and I'm sure there are others. It is a consequence of the spring ice breakup coupled with strong sustaining winds on large northern lakes. The warming spring weather melts the ice close to shore first, making the ice on the lake free-floating. The ice in the middle of ...


8

Developing since 2014, the crack was projected in 2015 to lead to "the largest calving event since the 1980s," according to this report in The Cryosphere journal by glaciologists studying the region. From 2010, "Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years" says that the largest break-up event in that period ...


7

There is a decent explanation in Glacier Man Science 30 Oct 2009: Vol. 326, Issue 5953, pp. 659-661. (alternative link) Norphel’s idea was to divert the lost winter water from its course down the mountain, along regularly placed stone embankments that would slow it down and allow it to spread and trickle across a large, shaded surface depression ...


7

A first-order estimate is about 5%. This is a trickier question than it first appears because of ice shelves. Quoting from Kusky (2014): Ice shelves form where ice sheets move over ocean waters and form a thick sheet of ice floating on the water and attached to the land on one, two, or three sides. Their seaward sides are typically marked by a steep ...


7

It's called ice shove. Ice on the lake melts whiles the wind push and pile the thin sheets ashore. I don't know how common it is but I've seen it in much smaller scale in European lakes. However, this occasion made it to the news. It does indeed look rather spectacular! The fresh water of the Great Lakes in combination with cold air often create beautiful ...


7

Calculated Earth is one of the better tools for this, you can either zoom in and get various flood stages or set a specific flood stage and see what would flood, it is in metric though so you may need some conversion software to deal with the units for you, depending how familiar you are with metric.


6

According to "Permafrost, active-layer dynamics and periglacial environments of continental Antarctica" South African Journal of Science 98. pages 82-90: Only 25% of Antarctica has permafrost, as the material beneath thick ice sheets is not permafrost. The deepest permafrost occurs where there is no ice sheet. The deepest permafrost in the Antarctic is ...


6

First of all, the Earth does not receive heat from the Sun, it receives visible light that is absorbed by the surface of the Earth and then heat is re-radiated back into the atmosphere. If the surface is ice/snow, most of the light from the sun is reflected back to space. Sunlight will sublimate a little bit of the ice, but it is normally replenished at a ...


5

userLTK has explained that not all of the ice in the Antarctic stays frozen all the time. But perhaps there's a more basic view needed : sunlight in temperate areas melts all of the ice quite quickly, so why doesn't the same happen in Antarctica? There are a number of reasons, but the simplest (and probably most important?) is one of geometry, and the way ...


5

No-one has mentioned fish yet. Do you have fish or other animals in your pond? Not only do they provide a small amount of warming, their movement will help prevent ice forming.


5

Upper Mississippi river near St Paul Minnesota is closed December - March. US Army Corp of Engineers is responsible river navigation in the United States. From winonapost.com, (from 2015) the article states that all vessels need to be south of Lock and Dam 9, near Lynxville, Wisconsin. Sounds like the upper river is closed so locks can be dewatered and ...


4

The variable you need to consider to understand the problem is the pond's depth. I bet that in contrast to your pond, shallow puddles around did freeze. The water is denser at 4°C, so to freeze the surface you need to cool down the whole pond to 4°C. Otherwise, when water in the surface cools down to 4°C, it would sink and be replaced by warmer water from ...


4

In addition to the accepted answer from Casey, it is likely that the sun is warming the pond over the course of a day more than it warms the thermometer used for the temperature readings you are quoting, as thermometers are kept inside a Stevenson Screen.


4

As has been abundantly said in the comments and on meta, there is no proper answer to this question in the current state of knowledge. But indeed we can at least check if we can come up with a rough estimate (and thus try to see from where this 20% estimate comes from). Let's first look at the main known glaciations: The Current one: there is indeed a ...


4

There are a few things that come into play when you talk about the radiative forcing of clouds, or their effect on the climate budget. "Cloud" is a pretty wide-sweeping definition. Scientists are still trying to fully understand and quantify these effects. Clouds do not vary only in where they are in the atmosphere but also in their phase (ice versus mixed ...


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