Greg Studen | 04/07/09 @ 2:00pm
The beauty and the austerity of the Arctic have long captured the imagination of artists and writers. Whether it's the light, the endless tracts of wilderness, or the featureless snow and ice of the far north, the Arctic has a magical quality which inspires the imagination as if we have stepped into a dream.Now that dream threatens to become a nightmare. Evidence is mounting that the the frozen north is rapidly turning into the unfrozen north. According to climate scientists, the dangers from widespread and severe Arctic melting are truly frightening for the future of our planet. Why is the Arctic meltdown so scary? To understand the answer to this question, we have to look at the role of the frozen polar regions in the heat economy of the Earth. Overall, the heat balance of our planet is maintained by a complex circulation of heat from the equator to the poles. The far north regions play the role of absorbing heat from the tropical oceans (and also, but less so, from the land). They are capable of this role because the high latitudes are subject to much less direct solar heating, and because, covered with white ice and snow, they reflect a substantial portion of their heat back into space.There are two other processes in the polar regions that are vital to understanding how global warming works. First, the Arctic is potentially a source for the production of vast amounts of carbon dioxide (CO2), the main greenhouse gas, and methane, another very powerful greenhouse gas. Both of these gases are created by the decaying, or oxidation, of organic--that is, carbon containing--compounds, chiefly plant and animal remains. In the Arctic, temperatures generally are cold enough that decay of organic material is slowed down to a crawl or stopped completely. Over time, billions of tons of organic materials have built up in an undecayed state, locked in time in the frozen soils of the permafrost. With warming, the permafrost melts, and these materials begin to decay, releasing the CO2 and methane into the atmosphere. In addition, much of the methane and CO2 that has already been created by the slow decay of plants and animals under frigid conditions is stored in waters of the polar regions. Ice has the ability to literally physically trap these greenhouse gases, which are now locked in a vast, icy storehouse. Over many years, millions of tons of these gases have been captured in ice structures at the bottom of the polar oceans, under conditions of cold and high pressure. Warming of the land and ocean waters allows the gases to escape, adding substantially to the CO2 and methane in the atmosphere.The amounts of methane and CO2 that could be generated in the Arctic by the decay of organic matter, or release from frozen stores, are extremely large. The danger is that release of these gases could trigger what is called a "runaway" process of greenhouse warming. In this situation, there is a positive feedback loop, where the gases released cause warming, which causes more gas to be released, which causes more warming...and so on until a new equilibrium in the Earth's heat balance is reached--at a much higher average temperature. Where this process might stop is not known, but scientists have projected that the overall average temperature could be 5-8 degrees centgrade (9-14 degrees Fahrenheit) warmer if the runaway effect takes hold in the Arctic. This could happen very quickly, with much of the warming by the end of the 21st century. The frozen lands of the Arctic give us an excellent example of a threshold effect, or what is commonly called a tipping point, in the process of global warming. Ordinarily, we would expect a gradual progression of effects. Winters may become shorter, and summers hotter, but they should change slowly over time. The range of various species of animals and plants may shift northward, but again a little bit at a time. In the Arctic, things are different. The problem is that water melts at 32 degrees Fahrenheit. This means that as the average temperature over large parts of the north lands rises to even a little bit above 32 degrees, ice turns to water, and the processes described above begins to release greenhouse gases on a massive scale. Melting ice also creates the large bodies of open water in the Arctic seas that absorb additional heat. Warmer waters in turn generate warm winds that blow over the land. The metabolism of decay micro-organisms in the melthing permafrost gives off additional heat. These processes set off the positive feedback loops that drive the progress of rapid warming. Already large areas of the Arctic are melting. The positive feedbacks are very powerful, and have so far raised the average temperature by 3-5 degrees centigrade in some areas. Scientists are now seeing a widespread melting of the permafrost, which is turning large areas of previously frozen ground into lakes. Methane is bubbling steadily out of these lakes. In addition, a large quantity of methane is escaping out of the Arctic ocean along the Siberian coast, as warming waters from Russia's far eastern rivers melt the ice formations that have trapped the methane deep in the ocean. Arctic sea ice is disappearing rapidly in the summertime, and summer ice may be gone by the end of the century. As the ice declines in area, the warming process is accelerating. These changes highlight the misleading implication of the seemingly small recent change in the Earth's overall average temperature, which is in the range of one degree centegrade higher over the last one hundred years. The Arctic regions are warming much faster. This will have the effect of driving the Earth's average overall temperatures upward at a considerably higher rate in the near future. As overall temperatures rise, sea levels are going up, storms are worsening over tropical regions, and patterns of drought and flood over the continents are becoming more severe. Because of the long residence times of CO2 in the atmosphere, and the power of feedback mechanisms, we are quickly approaching a point where many climate scientists believe that serious warming will be unstoppable.So the irony is that the frigid Arctic may be decisive in determining how quickly and severely the Earth warms. If we do not act soon to stop global warming, our Arctic dreams may indeed turn into nightmares.