Arctic Sea Melting Enhancing the Effect of Global Warming in High Latitudes
The world warmed by about 0.7°C in the 20th century. Every year in this century has been warmer than all but one in the last century (1998). If carbon-dioxide levels were magically to stabilize where they are now (almost 390 parts per million, 40% more than before the industrial revolution) the world would probably warm by a further half a degree or so as the ocean, which is slow to change its temperature, caught up. But CO2 levels continue to rise. All this affect the ice pack in the Arctic. As temperature rises, ice melts. This causes many problems. A change to the reflectivity on the surface of the earth; which is called the albedo, affects the amount of solar radiation absorbed by the Earth. As Arctic sea ice continues to melt it exposes open water which is less reflective and causes the albedo to decrease. The reduction in albedo allows more light to be absorbed by the ocean. As the ocean water warms, more heat is added to the air creating a positive feedback and driving Arctic temperatures ever higher. The reduction in sea ice is having a significant impact on arctic ecosystems. The Arctic sea is home to a wide variety of wildlife, including polar bears, arctic foxes, seals, walruses, and whales, fish species such as Arctic cod and char, and sea birds such as guillemots, auks, and eiders. Geoscientists all agree that the Arctic has been and will continue to be dramatically impacted by global warming and the other way around. A great amount of the surface in the Arctic is underlain by permanently frozen ground called "permafrost". They highest layer experiences seasonal thawing. Through research recent studies have shown that climatic warming my result in a 12 to 15% reduction in the area covered by permafrost and a 15 to 30% increases in the thickness of the active layer. As temperature rises permafrost melts, releasing stored carbon, but just as importantly, methane. Increased warming results in more permafrost melting pushing the earth system ever forward into a future enhanced greenhouse environment. When permafrost melts, water collects in small ponds on the surface increasing the heat gain nearly ten-fold. The additional heat continues to melt the underlying permafrost causing it to collapse and increasing the size of the pond. This positive feedback further degrades the permafrost. As we know carbon dioxide makes up a greater proportion of the atmosphere by volume, but methane absorbs energy much more efficiently. Increased warming in the atmosphere from the arctic permafrost melting at high latitudes may cause an increase in the release of methane from bogs. Methane release from organic decomposition in wetlands coupled with carbon dioxide from melting permafrost will drive greenhouse gas levels higher, creating warmer temperatures.
It is likely that greenhouse-gas-induced Arctic warming is one of the major factors for the significant decline in sea ice area and thickness observed in many Arctic seas over the past few decades. General circulation computer models of the atmosphere project that greenhouse warming will occur more intensely over the Arctic in the future than any other part of the planet, largely because melting snow and ice will replace lighter surfaces with darker tundra and ocean surfaces, lowering the albedo, decreasing the sunlight reflected from the Arctic, and so accelerating the warming trend. The warming observed so far over much of the Arctic land masses is only a small fraction of the intense 8-16 degree Celsius increase in winter temperatures projected by computer models if greenhouse gas levels double over the next few decades. What effect would a greenhouse gas doubling have on the Arctic ice pack? This is a difficult question because Arctic warming will have complex effects on air and ocean circulation, clouds and precipitation. Nevertheless, most computer models project a dramatic decline in Arctic...
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