Glacial melt: Coming to a sea near you
Image: Kagen McLeod
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Key concepts
Ice and water
Oceans and land
Climate change
From National Science Education Standards: Natural hazards
Introduction
Look outside. Can you see any ice? What about in the middle of summer? Believe it or not, about 10 percent of the planet's land is actually covered in ice—year round! The ice in these places, such as Antarctica or on very high mountain ranges, is usually in big pieces called glaciers or ice sheets. It can stay there if the temperature stays cool enough and enough snow falls to replace whatever ice melts off when the temperature gets above freezing.
All of that ice is made from an awful lot of water. And when that water melts, much of it ends up in the oceans. How might that affect us? We can get a fast-paced peek at this process that is going on right now with just a couple of ice cubes and some clay.
Background
Antarctica is a solid continent just like North America or Asia. Because it gets so little warmth from the sun, it is cold enough to be covered with ice all year—at least for now. (The Arctic ice around the North Pole, on the other hand, is mostly covering ocean.)
But when average temperatures rise, as is happening in many places around the world because of climate change, big blocks of ice melt more quickly than they can grow during the winter. Thus, less moisture is trapped in ice sheets, then more is found in liquid form. And a lot of this extra water ends up in the oceans, leading, eventually, to higher sea levels.
Climate change is a shift in overall global temperatures and weather, and it is already affecting ice sheets and glaciers across the globe. When ice pieces fall off landmasses, such as Antarctica or Greenland, and into the ocean, the ice melts even faster. Scientists currently predict that sea levels will be at least three feet higher by 2100.
Materials
• Small bowl
• Ice cubes
• Modeling clay
• Toothpicks
• Warm water
Preparation
• Pull off two portions of modeling clay. (Size will depend on the size of your bowl and the size of your ice cubes—they will need to be big enough for of them to hold two ice cubes on its surface and for both of them to stick out of the water.)
• Stick the clay to opposite sides of the bottom of your bowl.
• Mold one piece of clay to be flat, with a surface just large enough to hold two ice cubes. This will be Antarctica.
• Shape the other piece of clay so that it is slightly higher than the first piece—this piece will represent an ice-free continent where people live. Make some parts flat and give others hills or mountains.
Procedure
• Place two ice cubes onto the lower flat piece of clay (Antarctica).
• Start slowly pouring the warm water into the bowl until it almost reaches the top of your Antarctica clay. Your other clay continent should still have area that is mostly well above water. The water represents the ocean.
• Because the air around the ice cubes is warmer than freezing (as it is now), what do you think will happen to the ice cubes? If you were able to keep the air around the Antarctica area below freezing, how would that change what happened to the ice cubes?
• Pour just a little bit more water into the bowl so that the water level just reaches the bottom of the two ice cubes. (In Antarctica, the ice actually extends beyond the land and over part of the ocean so some of it is in contact with water.)
• Note where the water level is on your dry continent clay by placing two toothpicks vertically into the clay where the water meets the clay. Compare the flat areas with the hilly ones.
• Watch as the ice cubes start to melt. What happens to the water level in the bowl?
• As it rises, position another toothpick or two to mark the new level.
• In Antarctica, Greenland and other places where big ice sheets are surrounded by the ocean, sometimes big chunks of ice fall into the ocean after they have started to melt. To replicate this process, push one of the ice cubes into the water. (You might notice waves hitting your dry continent—although this is closer than it a neighboring continent in the real world, scientists think that a big piece of ice could cause large waves to hit land far away.)
• Watch as the two ice cubes continue to melt. Which ice cube melts faster? What happened to the water level on your dry continent? Were the flat areas affected differently than the hilly ones?
Read on for observations, results and more resources.
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28 Comments
Add CommentWith an average temperature of -50°C, Antarctica will warm to melting in 3000 years if we double the current rate of global warming. By the way, glaciers that are calving are growing, not melting.
Reply | Report Abuse | Link to this"By the way, glaciers that are calving are growing, not melting."
Reply | Report Abuse | Link to thisNot necessarily. Calving only means glaciers are moving towards the sea. This *could be* because they are growing or it *could be* because they are melting and are moving faster towards the sea (on meltwater lubricant).
I love how a casual observer like you thinks they immediately know more than actual scientists in the field that take measurements and have actual data.
Great debunking, candide. I would also like to note that the average temperature of Antarctica doe not mean that EVERY part of the continent is that temperature. The West Antarctic Peninsula is warming faster than almost any other part of the world and is losing ice like crazy. West Antarctica in general is warming and losing a lot of ice as well. The reason for this disparity is partly due to the way weather patterns are interacting with the higher air temperatures, but also because the ice sheets in the West are several thousand feet lower in elevation than the ice in East Antarctica. Since the ice elevation decreases as it melts, this could be another positive and non-linear feedback that can cause ice sheets to collapse much quicker than any model can predict. This holds true for the ice sheets in Greenland as well.
Reply | Report Abuse | Link to thisOh Dear! I recently relocated, again, to live in a little 166 square mile island in the Caribbean that depends on tourism for its income. Even a small rise in sea levels will cover our sandy beaches which is a huge part of our tourism appeal. A significant rise could gobble up much of our prime seafront real estate. A large rise could inundate almost a third of our dwelling space. Poor little Barbados! btw. Poor Manhattan too, etc.. etc...!!
Reply | Report Abuse | Link to this@skeohane, please look up the Dunning-Kruger effect. You seem to be the only one who hasn't figured out that you are clueless.
Reply | Report Abuse | Link to thisThe Supplemental Material in this Bring Home Science, and others that I have seen, do not display properly in Firefox. There appear to be 3 items, the right half of the right one is truncated. Making the window wider has no effect.
Reply | Report Abuse | Link to thisIt has been widely disseminated that the rate of melt is increasing at an increasing rate. Therefore a linear calculation like the one "skeohane" is attempting is totally irrelevant and disastrously inaccurate. One only has to look at a simple chart with a line concave to the point of origin to understand why.
Reply | Report Abuse | Link to thisIn actual physical terms, a not insignificant factor is the amount of methane gas being released when an area of ice is melted. An "average" calculation doesn't take into account those above average areas of warming on the ice sheet which release their methane. Because their contribution continually feeds back into the so called average rate of melting that rate cannot remain constant, but will continue to accelerate. The "current" rate of warming is useless for predicting in such a scenario, because the current or instantaneous rate of warming is changing moment to moment. I hope this is not the kind of error that has plagued current projections to date.
If the Earth is really warming then the polar ice sheets should be increasing in size. This is because the polar regions are not heated by the sun directly. A warming Earth would cause more moisture to condense in the polar regions, which means more ice.
Reply | Report Abuse | Link to thisThe fact that moisture transfers heat to the poles should be obvious to climate scientists. But those scientists ignore the obvious. Instead, they imagine that sea level rise is due to warming. In fact, sea level rise is due to global cooling since less moisture is moving to the poles where it freezes.
The Earth's poles act like the air conditioners for the Earth. More heat means more moisture and so more ice at the poles. Moisture is the refrigerant in the air conditioning cycle of the Earth.
The idea you present ignores thermodynamics and heat transfer.
Reply | Report Abuse | Link to thisThe First Law of Thermodynamics states that Heat can be neither created or destroyed, but it may be changed into other forms, such as mechanical, sound, or light.
The Second Law of Thermodynamics states that heat only flows from a hot body to a cold body.
An air conditioner is an excellent example of putting both the First and Second Laws, and Heat Transfer Principles into practice, in the design, construction and operation of air conditioning equipment. A refrigerator or freezer works in exactly the same way except they cool food and drink in an enclosed container.
When an air conditioner cools a room, it runs a predominantly liquid phase coolant through its network of inner heat transfer pipes where room air is fan forced over and under the pipes, to the compressor. This causes the partial liquid phase - partial vapor phase coolant to compress into a mainly liquid phase, and the compressor pumps the coolant to the outer heat transfer pipes, where the heat escapes into the outside environment, and the predominantly liquid phase coolant through its network of inside heat transfer pipes, completing the cycle.
To shorten the above description, physicists and engineers describe an air conditioner, refrigerator or freezer as a heat transfer pump. At the end of the day the heat has to go somewhere, and it is released to the outside environment.
Where does the heat from the moisture go at the poles? It cannot just disappear. The simplest explanation may be that the heat remains in the atmosphere above the poles, increasing the ambient polar temperatures.
The statement the earth's poles are not heated directly by the sun is incorrect. Again avoiding the Laws of Thermodynamics and heat transfer principles.
Take a look at Earth satellite image resources:
http://dbaron.org/sat/comp/#ant
Even scientists will not be in agreement as to the mechanics of global warming. None of what the article discusses happens in isolation from other regions and other Earth processes, such as the redistribution of rainfall, changing ocean currents, land inundated by rising waters, and land exposed by melting ice masses. It is simplistic and misleading to use the Antarctic/bowl of water comparison as a teaching model for something as complex and inter-related as Earth physical science.
Reply | Report Abuse | Link to thisThe issue that is being missed here is one of political indoctrination. There is an inherent assumption that any and all global warming is being caused by people.
Reply | Report Abuse | Link to thisAnd it is presented as a fait accompli to our children. Critical thinking and investigation not welcome at the SCIAM madras.
Is it not true that polar glaciers have been slowly receeding ever since the last ice age?
Reply | Report Abuse | Link to thisIs it not true that the anarctic ice cap is increasing?
If the glacier melt is as bad as what is reported, why was it necessary for the Univ. of Colorado to fabricate the amount of sea water rise?
If global warming is true, why has so many noted scientists come out against it?
If global warming is true, why did so many UN sponsored scientists fabricate false statisticts?
Global cooling is occurring. The Earth is like a steam engine in that moisture transports heat to the poles. Less moisture being trapped at the poles as ice proves that global cooling is occurring already. A condenser is not heated like a boiler. The poles are heated by condensation not by sunlight. Winter is totally dark at the poles, and so it snows almost continuously.
Reply | Report Abuse | Link to thisClaiming that the poles are heated is silly. The poles are cooled, which means the primary source of heat comes from condensation, which releases an incredible amount of heat. Ice forms at the poles, and then the ice spreads outward due to pressure. Further from the poles the ice melts, in summer.
i think the comments here indicate why global warming is now popularly called "climate change", which makes more sense to me, since some places become colder, others warmer, drier, wetter, etc. It is really the redistribution of these conditions that is occurring. Makes me wonder also: what specific set of measurements are incorporated to ascertain the planet's temperature? All previous discussions of global warming/climate change at some point refer to ocean temps as an indicator, but i can't recall ever seeing references to air temps, or temps of, say large land mass features like deserts or forests.
Reply | Report Abuse | Link to thisWhat an excellent question, auntygravity, one that very few people seem to ask. How are temperatures measured? Over the last hundred years or so it's been done with thermometers at weather stations. Over the last 30 years or so satellites measure radiation in different wavelengths. To determine temperature prior to instrument measurements, tree ring width is used (and related methods). Are there problems with the accuracy of these methods? Yes. How do you account for "heat island" effects with increasing urbanization around weather stations? How do you account for changes in satellite altitude, differences in instruments, differences in cloud cover? How do you rule out other variables (rainfall, disease, etc.) that affect tree ring growth? How do you extrapolate the huge gaps in the remarkably small number of measuring locations to derive a temperature for the whole globe? Over what time interval do you measure to determine trends? You use statistical methods to try to eliminate other effects, but the results vary based on the variables used.
Reply | Report Abuse | Link to thisWhat an excellent question, auntygravity, one that very few people seem to ask. How are temperatures measured? Over the last hundred years or so it's been done with thermometers at weather stations. Over the last 30 years or so satellites measure radiation in different wavelengths. To determine temperature prior to instrument measurements, tree ring width is used (and related methods). Are there problems with the accuracy of these methods? Yes. How do you account for "heat island" effects with increasing urbanization around weather stations? How do you account for changes in satellite altitude, differences in instruments, differences in cloud cover? How do you rule out other variables (rainfall, disease, etc.) that affect tree ring growth? How do you extrapolate the huge gaps in the remarkably small number of measuring locations to derive a temperature for the whole globe? Over what time interval do you measure to determine trends? You use statistical methods to try to eliminate other effects, but the results vary based on the variables used.
Reply | Report Abuse | Link to thisSurveys indicate that the more people understand about climate science, the less likely they are to attribute global warming/climate change mainly to human activity and the less they are worried about its impact. Why? Because it becomes clear that a.) the science--even the measure of temperatures--is far from settled, b.) climate science has been heavily politicized by alarmists wanting to force their version of environmental policy on the rest of us, and c.) the current warm climate is far more conducive to abundant life on earth than the previous, periodic glacial periods. So by all means, let's teach our children as much as we can about climate science so they can make informed policy decisions when they grow up.
Reply | Report Abuse | Link to thisi'm aware of the various ways meteorological measurements are taken: my question was why ocean temperature is commonly the only measurement referred to in discussions of global warming/climate change, which you did not answer. the "alarmists" you refer to are no more guilty of forcing their agenda on us than are profiteering commercial interests who's only concern is to sell consumer goods to us at the expense of depleting natural resources, degrading the environment and creating enormous waste disposal problems. Hundreds of billions more of advertising $$ are spent promoting an "exploit/consume/discard" economy than are spent on advertising promoting environmental causes and awareness. It seems incongruous to talk about teaching our children about climate science, while simultaneously claiming climate scientists have an "alarmist" bias. No study of climate science and climate change can be valid and useful if it ignores the effect the activities of 8 billion humans have on climate and environment. Given enough time, climate change is inevitable with or without human intervention. But it is within our ability to both be better prepared for it, and to mitigate our contribution to it.
Reply | Report Abuse | Link to thisSo much mis-information here.
Reply | Report Abuse | Link to this"Is it not true that polar glaciers have been slowly receeding ever since the last ice age?"
No, that is not true. The ice ages are driven by shifts in the Earth's orbit called Milankovitch Cycles. These cycles occur over ten's of thousands of years, with the primary cycle taking about 44,000 years. The warm peak of the current cycle was about 6000 years ago. So the emergence from the last ice age ended about 6000 years ago and since then we have been in a gradual cooling, not warming period. A new ice age is due to start in about 10,000 years. None of that has anything to do with the present sharp warming caused by extra CO2 in the atmosphere produced from burning fossil fuels. Jere is one of many studies on the subject.
http://dx.doi.org/10.1126%2Fscience.194.4270.1121
"Is it not true that the antarctic ice cap is increasing?"
No, that is not true. Antarctica is losing over 100 giga-tons of ice per year.
More mis-information:
Reply | Report Abuse | Link to this"If the Earth is really warming then the polar ice sheets should be increasing in size. This is because the polar regions are not heated by the sun directly."
No, the Earth's axis tilts 23.4 degrees. This causes the poles to be in complete darkness in the winter and to have all day sun in the summer. So, far from "not being heated directly by the sun" as you state, in the summer time the poles are heated continuously, 24-hours a day, by the sun.
Climate science is filled with misconceptions. Earth's climate is self-stabilizing. For example, as Earth warms, more vapor circulates towards the poles of the Earth. This causes an increase in ice and snow at the poles, which causes more reflection of sunlight, which prevents overheating.
Reply | Report Abuse | Link to thisSelf-correcting systems oppose change. This means sea level must rise as the Earth cools. This causes more sunlight to be absorbed by water and land (less reflection by ice).
Snow falls at the poles and then the snow spreads outward. The ice then melts in summer as it spreads outward. The poles are heated by condensation not by sunlight. Winter is totally dark at the poles. Since oceans are rising, this is proof that less ice is forming at the poles, which indicates less heat transport towards the poles, which occurs as the Earth cools (global cooling).
Vapor content of air increases very rapidly with temperature increase. But the rate of ice melting increases linearly with temperature increase.
The Earth now have so much heat in it that's why cleaning the environment is now really needed and because NASA has had their space shuttle system stopped, they decided to conduct an environmental cleanup drive. Though they are not spending money putting people into space, NASA will still be innovating. The innovation is going to be aiming into groundwater, not into space. The environmental cleaning will take decades to clean up, as it took years to cause. The spending budget for the cleanup is getting close to $1 billion. The proof is here: <a title="Huge spending budget for NASA's environmental cleanup" href="http://www.newsytype.com/9617-nasa-spending-billions-environmental-cleanup/">NASA will be spending billions on environmental cleanup</a>.
Reply | Report Abuse | Link to thisWe live about 50 meters from the ocean. There has been zero rise in seal levels. We spend a month each winter in Maui, also no rise of levels.
Reply | Report Abuse | Link to thisThe Chicken Littles are at it again
"Surveys indicate that the more people understand about climate science, the less likely they are to attribute global warming/climate change mainly to human activity and the less they are worried about its impact."
Reply | Report Abuse | Link to thisOnly if you exclude actual climate scientists in favor of idealogues and paid propagandists.
http://merchantsofdoubt.org
Here we have peer-reviewed scientific methods of measurement used over decades versus the 'jellyroll' method of measurement allegedly used during one month a year. I don't care whether you use metric or imperial jellyroll units -- I'll stick with the science.
Reply | Report Abuse | Link to thisGlaciers may be shrinking far faster than meltwater suggests.
Reply | Report Abuse | Link to thiswater can exist in three states (ice,liquid,vapour), and change from any one state to another. Sublimation is when ice evaporates. Very little research has been done on this phenomenon. To measure sublimation, you have to weigh surface ice at regular intervals, and ensure melt-water is captured seperately.
Ice packs around the world (perma frost) have received jolts of radiation causing internal rot (melting)! Cold of winter does not penetrate this ice.
Reply | Report Abuse | Link to thisRecent longatudinal eratic tipping of the earth that immediately changes it's exposure to moon and sun.
http://forums.randi.org/showthread.php?t=162045&page=3
Skohane and R.Blakely have the right idea ... Science is sooooooooooo hard! Oh, sure, science may be "factual." But is it Biblical? That's the correct test. Michelle Bachmann says so, for crying out loud. How much more credibility do you need? But the way, did you know that the word "science" cannot even be found in the bible? Ditto for "global warming." I rest my case. See how easy and satisfying that was? Myth-based cultures have been around for a lot longer than the fact-based cultures of the stinking, hippy scientists. Today's Republican party continues the proud traditions of common sense science, pointing out that the Earth cools every night after the sun goes down. Also, far from being endangered, polar bears are doing just fine in zoos around the world. And, it's a known fact that, with 4 percent of the world's proven oil reserves, America can easily drill our way to energy independence, since we only consume 20 percent of the world's oil now. How is that possible, you ask. Once again, I ask you to remind your two blinders, math and science. Then place your hands over your ears, throw open you pie hole, and repeat it, loudly, over and over. "Drill, baby, drill." This technique has worked for decades for the God-fearing Republicans, who are poised to completely transform Congress into a faith-based enterprise. Life will be so much simpler then. All this fuss about irreversibly polluting the Oglalla aquifer with spills from the Keystone pipeline? Who needs an aquifer named after Indians, anyway? It's probably firewater. Dirty, stinking welfare water. There's plenty of water in the grocery stores. I just brought home a couple six packs, and even recycled the cute, empty bottles. Talk about Green! Win-win. Keep fighting the good fight, Skohane and R.Blakely. Push comes to shove, just unconceal your conceal carry, and pump a couple rounds skyward. That tends to quiet down the room. America has most of the missiles, and Republicans have most of the guns. Now there's some meaningful math for you.
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