Even though the North Pole and South Pole are "polar opposites," they both get the same amount of sunlight. But the South Pole is a lot colder than the North Pole. Why? Well, the poles are polar opposites in other ways too.
The main reason that the South Pole is so much colder than the North Pole is because of the strength of the winds blowing around the poles. Antarctic winds are very strong and stop warmer air from mixing with the polar air. This also happens in the Arctic, but winds surrounding the North Pole are not as strong. Because of this, warmer air from the warmer mid-latitudes is able to mix with polar air, making the Arctic warmer.
Colder Then Ice
Both polar regions of the earth are cold, primarily because they receive far less solar radiation than the tropics and mid-latitudes do. At either pole the sun never rises more than 23.5 degrees above the horizon and both locations experience six months of continuous darkness. Moreover, most of the sunlight that does shine on the polar regions is reflected by the bright white surface.What makes the South Pole so much colder than the North Pole is that it sits on top of a very thick ice sheet, which itself sits on a continent. The surface of the ice sheet at the South Pole is more than 9,000 feet in elevation--more than a mile and a half above sea level. Antarctica is by far the highest continent on the earth. In comparison, the North Pole rests in the middle of the Arctic Ocean, where the surface of floating ice rides only a foot or so above the surrounding sea.The Arctic Ocean also acts as an effective heat reservoir, warming the cold atmosphere in the winter and drawing heat from the atmosphere in the summer.Answer originally published May 5, 2003. Rights & Permissions[missing "en." translation]The SciencesOn Thin Ice?Robert A. Bindschadler and Charles R. Bentley
Warm water generally gets more dense as it gets colder, and therefore sinks. This fact may lead you to believe that ice should form on the bottom of a lake first. But a funny thing happens to water as it gets even colder. Colder than 4 Celsius (39 Fahrenheit), water begins expanding and becomes less dense as it gets colder. As a result, close to freezing, colder water floats to the top and the warmer water sinks to the bottom. The density of water as a function of temperature can be seen in the plot on the right. Eventually, the coldest water, which has floated to the top of the lake in wintry conditions, freezes to form a layer of ice. Right when the water freezes to ice, the ice becomes significantly less dense than the water and continues to float on the lake's surface.
Ice is less dense than water because of the way it forms a hexagonal crystalline structure. Each water molecule consists of two hydrogen atoms bonded to the bottom of an oxygen atom. When ice forms, the hydrogen atoms of one water molecule form weak hydrogen bonds with the top of the oxygen atoms of two other water molecules. Lining up the water molecules in this pattern takes up more space than having them jumbled randomly together (as is the case in liquid water). And because the same mass of molecules takes up more space when frozen, ice is less dense than liquid water. For this same reason, water below 4 Celsius becomes increasingly less dense as it gets colder. Close to freezing temperatures, the molecules in the liquid water begin to line up into the space-filling hexagonal structure.
Since there were no thermometers in the ice age, the researchers developed models to translate data collected from ocean plankton fossils into sea-surface temperatures. They then combined the fossil data with climate model simulations of the LGM using a technique called data assimilation, which is used in weather forecasting.
If we take two ice cubes and add salt to one of them, then put each of them at room temperature, both of the ice cubes will absorb energy from the surroundings, and this energy as we said will contribute in breaking down the bonds between water molecules.
The freezing point of water is $0 \puC$, so water-ice slush stays at $0 \puC$. If it was lower, it would stabilize at the lower temperature. By adding salt, you are lowering the freezing temperature. The mixture stabilizes there and is colder.
When you dissolve $\ceNaCl$ in water, it will have to take energy from the system to break its structure so it can dissolve in water. This is the reason the water gets colder because the salt uses the energy from the water to solve it.Now let's look at why ice melts when salt is added. This is based on a so-called colligative attribute. These attributes are only dependent on the amount of substance. When you add particles to a solvent, its vapor pressure lowers. This will result in a higher boiling point(using salt for cooking) and a lower freezing temperature for the solution.
Melting is endothermic and freezing is exothermic. We never observe water warm up when it freezes because more energy has to be lost from the system before more water freezes. When water freezes from being in cold air, the release of heat actually slows down the freezing. When you add salt to a mixture of water and ice, it causes more ice to melt by depressing the freezing point and not by adding internal energy so it actually gets colder.
Water molecules from the ice cube will diffuse into the salt solution, diluting it. Energy is required for the transition from solid ice to water: the amount of heat required to melt ice is 68.3 kcal/mole (heat of fusion). This energy comes from the salt solution, reducing its temperature. The ice cube will continue to melt (turns from solid to liquid) as long as it is not in equilibrium with the solution. The ice cube does not melt because the surrounding liquid has a lower freezing point, it melts because the surrounding solution is less than 100% water. The surrounding solution is already colder than 0C and the ice cube is still pure solid water at 0C. In other words, the driving force is a non-equilibrium of concentration. At the beginning of the experiment, there was thermal equilibrium (everything at 0C), but a concentration non-equilibrium forced the melting of ice by heat energy from the solution. Freezing point depression characterizes a solution, but is not a driving force.
In any reaction, a change in enthalpy is a measure of the heat absorbed or released during that reaction (assuming a constant pressure, yadda yadda). In general, all things being equal, things want to give off heat. By giving off heat they have a lower internal energy. Things want to go to a lower energy state. Things are lazy. It takes energy to break ice molecules free of the crystal lattice, so there is less energy stored in an ice cube than in water at the same temperature and pressure (cause I had to dump in heat to make it into liquid water). This heat that has to be added to ice to make water is called the enthalpy of fusion (or the heat of fusion). The heat of fusion of water is about 80 calories per gram, meaning that the heat required to melt one gram of ice is sufficient to heat one gram of water all the way from 0 to 80 C! Remember: melting ice requires heat (the heat comes from your drink so your drink gets colder). Making ice gives off heat, so enthalpy favors water turning to ice.
I am following this idea, but there is one thing I do not understand. If melting ice absorbs heat (read: gets hotter), and ice melts at 0 degrees C, and your ice is also 0 degrees C, then how, upon absorbing heat, does it remain ice?
Antarctica, the coldest place on Earth today, was even colder during the last ice age. For decades, the leading science suggested ice age temperatures in Antarctica were on average as much as 9 degrees Celsius cooler than the modern era. By comparison, temperatures globally at that time averaged 5 to 6 degrees cooler than today.
That paper, focusing on the South Pole ice core, found that ice age temperatures at the southern pole, near the Antarctic continental divide, were about 6.7 degree Celsius colder than today. The Science paper finds that across East Antarctica, ice age temperatures were on average 6.1 degrees Celsius colder than today, showing that the South Pole is representative of the region.
The new papers employ two techniques that provide the necessary calibration. The first method, borehole thermometry, takes temperatures at various depths inside the hole left by the ice drill, measuring changes through the thickness of the ice sheet. The Antarctic ice sheet is so thick that it keeps a memory of earlier, colder ice age temperatures that can be measured and reconstructed, Fudge said.
"In North America and Europe, the most northern parts were covered in ice and were extremely cold. Even here in Arizona, there was big cooling," Tierney said. "But the biggest cooling was in high latitudes, such as the Arctic, where it was about 14 C (25 F) colder than today."
Since there were no thermometers in the ice age, Tierney and her team developed models to translate data collected from ocean plankton fossils into sea-surface temperatures. They then combined the fossil data with climate model simulations of the LGM using a technique called data assimilation, which is used in weather forecasting.
"What happens in a weather office is they measure the temperature, pressure, humidity and use these measurements to update a forecasting model and predict the weather," Tierney said. "Here, we use the Boulder, Colorado-based National Center for Atmospheric Research climate model to produce a hindcast of the LGM, and then we update this hindcast with the actual data to predict what the climate was like."
"If we can reconstruct past warm climates," she said, "then we can start to answer important questions about how the Earth reacts to really high carbon dioxide levels, and improve our understanding of what future climate change might hold."
Or you can mix it up with a contrast bath to increase blood flow, reduce pain and swelling, and promote healing. Get two tubs or containers large enough for your painful area ready with warm and cold water. Soak in the warm tub for about 5 minutes and then plunge into the cold tub for about 1 minute. Go back to the warm for a few more minutes and then the cold for a minute. Repeat four or five times. 2ff7e9595c
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