I am an avid reader of The Onion. For those of you who don’t know what I’m talking about please be rest assured that I’m not some sort of weirdo who looks for messages in tea leaves and the like. Perhaps the name of a vegetable is a rather unusual choice for a satirical periodical, although I would have to disagree with anyone who felt that any prior publications of this genre had set lasting precedents. The more absurd the name is the better, and as we all know, absurdity is inherent to human existence. To clarify this thought I will kindly refer you to Scientologist actors with the surname of Cruise and to pop stars who don’t know when to call it a day with the plastic surgery. Thankfully, such selfless individuals provide us with an abundance of high quality entertainment. If we feel like having a good laugh at their expense, might as well do so while reading an oddly named, hilarious publication. The Onion it is.
Because I read The Onion so frequently and with such enthusiasm, I can quote many of the memorable phrases with some degree of accuracy…maybe not with the same familiarity the Republican Supreme Court Justices display with the Ten Commandments, but then again, that would be a difficult task indeed. My obsession with The Onion rather alarms my mother who wishes I paid similar attention to the Bible of her Mennonite heritage. Unfortunately, another lifelong love of mine, the Simpsons, has ruined any hope of me ever rising before noon on Sundays. Sorry Mom. You see, humour isn’t necessarily appreciated in all church settings (recall that Mennonites don’t drink or dance), and I happen to find Our Saviour’s name humorous. Yes, blame it on Homer. Some of you may recall the episode where he is sent away by the Good Reverend Lovejoy to do missionary work (which he botches horribly I might add). As he flies away on a plane (to avoid the wrath of the fabulous PBS tag team of Big Bird and the Teletubbies) Homer repeatedly shouts out, “Save me Jebus!” Apparently he really was dreaming of dancing bears during the sermons. Anyways, enough about cartoons, religion, and my lame excuse for not going to church – let’s get back to the story. Like any other newspaper, The Onion has headlines, feature articles, editorials, and yes, even horoscopes for those who require extra assistance. When I was asked to write a piece on climate change, I immediately thought, “Ha!” (not “Eureka!” as will be explained later). I’m sure you will be very surprised to hear that a headline from the May 30, 2002 Onion issue popped into my head. Atop of a photograph of a large floating sheet of ice was the headline, “Ross Ice Shelf Embarks on World Tour.” The first time I read this I was confounded (‘real confused like’ for those Republicans). Rising global temperatures, melting glaciers, inanimate objects giving concerts…I didn’t quite know how to feel. Should I be depressed or doubled-over?
Before deciding on an answer, I thought a little research might be in order. First off, I needed to determine what an ice shelf was. A little Google action quickly took care of that problem. According to our good friends at Wikipedia, an ice shelf is a “thick floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto an ocean’s surface.” The key message I took from this definition was that an ice shelf is a floater; even before parts of it begin to circumnavigate the globe. With this in mind, a number of seemingly legitimate questions came to mind. Why are ice shelves breaking up? What are the consequences of melting ice shelves? Who will open for U2 if the Ross Ice Shelf melts? In response to the first of these queries, you will be relieved to know that ice shelves are continually undergoing calving, a process that causes them to release icebergs into the ocean . Calving allows an ice shelf to achieve a sort of mass equilibrium that is necessitated by continual snow build-up and subsequent ice formation. I think we can be fairly certain that the headline in The Onion is referring to the fact that rising global temperatures are speeding up calving, and that the overall mass of the Ross Ice Shelf is slowing being degraded as a result. Thankfully, only a small fraction of the Ross Ice Shelf is on tour for the time being.
One of the major fears of the seers of drastic climate change is that melting glaciers will cause ocean levels to rise dramatically; up to 69 meters by some accounts [Houghton et al., 2001]. To tackle the second question posed in the previous paragraph, what we really need to do is determine the effect, if any, of a melting ice shelf on sea level. For a thorough analysis of this situation, let’s do the logical thing and go back to ancient Greece.
In 275 BC, a military leader seized control of the independent city-state of Syracuse; no doubt inspiring future US foreign policy in Latin America. To commemorate his proclamation as king ten years later, Hiero II paid a prominent Syracusan craftsman to fashion an ornate crown out of a quantity of gold. Sometime after receiving the finished product, Hiero became suspicious of the craftsman’s integrity. Fearing that he may have been tricked, Hiero asked a scholarly relative by the name of Archimedes to determine if the crown was indeed constructed entirely of gold. In his account some two hundred years later, the Roman architect (part-time historian?) Vitruvius noted that Archimedes figured out the problem while bathing himself in a tub one day. He observed that a greater volume of bath water was displaced when he submerged a larger fraction of his body. By this same logic, Archimedes reasoned that if identical masses of silver and gold were submerged in water, the silver would displace more water because it has a larger volume (i.e. lower density). By comparing the amount of water displaced by the crown and by an equivalent mass of gold, the king would be able to determine if the craftsman had replaced some of the gold with a cheaper metal! Vitruvius goes on to state that Archimedes jumped out of the tub excitedly shouting “Eureka!” and ran home naked. No word on whether he was arrested for public exposure.
So why have I included a Greek history lesson in an article that claims to deal with climate change? Well, Archimedes is the father of hydrostatics: an “interesting” scientific field that discusses floating objects, submerged objects, and buoyant forces. As hydrostatics can be used to explain the effects of melting icebergs on sea levels, it is rather relevant to our discussion of climate change. To start off with, let’s state the obvious: frozen water floats in liquid water. If you don’t believe me, refer to my all-time most hated movie: Titanic. The problem with icebergs is that unless you are a sea-dwelling creature or a submarine, you can’t really see a whole lot of them. As has been repeatedly rediscovered over the years by lousy nautical pilots, floating ice is almost entirely submerged (89.5% to be exact).
Like any floating object, ice displaces a quantity of the liquid it is immersed in. To verify this idea of ‘displacement’ please perform the following experiment: put your Speedos on, place a dry towel by the edge of a full pool, and cannonball away! If everything goes according to plan you will have a damp towel, indicating that you ‘displaced’ water from the pool onto the pool deck. The question of the day is: How much? From earlier discussion we know that a fully submerged object will cause an equal volume of water to be displaced. This is a seemingly trivial result. Where the object is located, the water cannot be. Thus, 500 cubic centimeters of sunken pirate treasure (or a Syracusan crown for that matter) will displace exactly 500 cubic centimeters of water. The same is not true for floating objects as they displace a weight of fluid equal to their own weight. To fully understand this statement, let’s start with a few basics. Pretend you’ve just stepped onto a bathroom scale and the scale spits back some politically correct number in politically correct units (kilograms NOT pounds). One might be tempted to say, “Keep me away from that chocolate cake. I weigh too much.” In reality, you do not ‘weigh’ 60 kilograms. You have a MASS of 60 kilograms. If you know any physics nerds, engineers will do, please mention this conundrum to them and they will be more than happy to explain (if you happen to meet one at a party, it can also be a good way to avoid any potential Star Trek conversation). As I happen to have studied some physics, I will briefly discuss weight and hydrostatics – and yes, I promise not to write it in Klingon. However, if you find yourself reading this next passage and saying, “Turn down the suck,” please appreciate that while science can be very entertaining, Fubar (which you’ve probably seen far too many times by the way) has set the bar pretty high. Anyways, here we go…
Weight is a measurement of force. The strength of Earth’s gravitational field is approximately 9.8m/s2 at sea level. This means that a television thrown out of a 9th floor Gage tower window on the day of Arts County Fair will accelerate towards innocent bystanders in such a fashion that it’s vertical velocity increases by 9.8m/s during each second it is in flight (ignoring air resistance of course). I’m thinking that a direct hit from a large meteor might be a slightly more dignified way to go…although neither a TV nor a chunk of alien-encrusted space rock is likely to result in the awarding of a prestigious (and posthumous) Darwin award. Anyways, with our newfound understanding of gravity we are now in a position to quantify weight. By referring back to our 60 kg person we can determine that they exert a gravitational force of 588 Newtons (60 kg x 9.8 m/s2) on the ground. Another way of stating this same information is to say that the person has a weight of 588 N. Thus, if this person were of a floatable body composition, they would displace exactly 588 N of water if lying in a pool (face up is always preferable). Believe it or not, this seemingly trivial piece of information will allow us to determine the effect on sea level if an iceberg or ice shelf melts.
Let’s pretend we have a large tub of water, into which we drop a block of ice weighing 30 N. For simplicity, we will assume that the ice and the water are of the same elemental composition (pure H2O with no chlorine, metal ions or other troublesome contaminants). For all of you budding thermodynamicists out there, understand that the ice will be liquefied as it has been placed into contact with heat reservoirs (i.e. air and water). Logic tells us that thermal energy will flow from the heat reservoirs to the ice, increasing both the temperature of the ice and the entropy of the universe in the process! Upon melting, the 30 N block of ice will become 30 N of water. As this water has the same volume as the water that was originally displaced, the level of the water in the tub will not change after the ice melts! In reality, the situation for ice shelves is slightly more complicated. Coleridge’s The Rime of the Ancient Mariner provides us with some valuable insight as to the composition of seawater: “Water, water, every where/ Nor any drop to drink.” As you are well aware and have no doubt guessed, the glittery-eyed Mariner is alluding to the fact that seawater contains salt, which makes it bad for drinking but good for curing Albatross. The Ross Ice Shelf, on the other hand, is comprised of pure water with little to no salt content (ice crystals like to arrange themselves in regular formations – any salt crystals present are gradually pushed out). So unlike the example previously discussed, ice shelves and the water in which they float have different compositions. This will require us to perform some additional analysis to determine if a change in sea level occurs when the floating ice melts.
If a 30 N block of ice floats in a tub of seawater, 30 N of seawater will be displaced. When the block melts, 30 N of freshwater (just over 3 litres) will be mixed in with the seawater, displacing an equivalent volume. The freshwater is essentially ‘replacing’ the seawater that was displaced by the ice. To determine whether or not the water level in the tub will rise or fall, all we need to do is compare the volume of 30 N of seawater with the volume of 30 N of freshwater (note that any weight of 30 N at the Earth’s surface corresponds to a mass of 3.06 kg). If the seawater has a larger volume, the water level in the tub will drop after the ice melts; the converse statement is also true. As seawater is denser than freshwater due to its salt content, 3.06 kg of seawater will occupy a smaller volume than 3.06 kg of freshwater. Thus, the water level in the tub will rise when the block of ice melts because the smaller volume of seawater is ‘replaced’ by a larger volume of freshwater! If we assume that the tub used in this example has a surface area of one square meter, the actual increase in the water level will only be a fraction of a millimeter. This leads us to the rather mundane conclusion that a floating block of ice such as an ice shelf or an iceberg won’t exactly cause a flood of Biblical proportion when it melts.
Let’s recap…I told you that there is enough water stored in all of the glaciers on Earth to raise the sea level by up to 69 meters if they were to melt. We then went on to prove that of this 69 meters, the maximum contribution of floating ice shelves and icebergs would be a few millimeters. With this in mind, a logical question might be, “Then what is causing the estimated sea level rise to be so large?” The answer is quite simple: land ice. Antarctica and Greenland are covered in massive ice sheets. If these glaciers were to melt, all of the runoff would directly increase the volume of water held in the world’s oceans, accounting for over 99% of the predicted increase [Houghton et al., 2001]. As the volume of ice held in mountainous glaciers and ice caps is so much smaller than that held in the ice sheets, the predicted rise due to their melting would account for the remainder (about 0.5 meters) [Houghton et al., 2001].
So what is the take-home message?
Even if all of the icebergs and ice shelves in the world were to melt, the direct impact on sea level would be an increase of a few millimeters at most. There are even some who believe that we would see a drop in sea level if this were to occur. Water is densest at 4oC and by liberating molecules of water from ice through the melting of floating glaciers, the total population of molecules at this temperature is bound to increase, leading to denser, more compact oceans. This might even be true, but by arguing about whether the sea will rise or fall by 5 or 6 millimeters, we are really missing the point. The fact of the matter is that while the slow destruction of the Ross Ice Shelf isn’t going to kill us, it is ultimately a sign of things to come. I ended up laughing at the ‘World Tour’ headline, but I probably shouldn’t have; climate change is happening around us and there is really nothing all that humorous about it. Today we are dealing with melting icebergs and ice shelves that aren’t causing significant changes in global ocean levels. But what about tomorrow? If we don’t act now to develop a more sustainable approach to life, the land-bound ice sheets in Greenland and Antarctica will eventually melt due to rising global temperatures and the consequences will be severe; nations will be flooded, disease will be spread, and countless lives will be claimed. At this time, we cannot afford to apathetically hide in the shadows like T.S. Eliot’s Hollow Men. We need action, and all of the global community would be wise to ratify and implement the Kyoto protocol immediately. Maybe it doesn’t contain all of the answers, and maybe it doesn’t go far enough, but it is a start that we can build on. Oh, and by the way, I still haven’t heard from Bono; it appears as though he is rather annoyed with Canadians at the moment.
2. Houghton, J.T. et al. Intergovernmental Panel on Climate Change Report. Climate Change 2001: The Scientific Basis. Cambridge University Press, 2001.
3. The story of Archimedes and the Golden Crown can be found at this website