| Lesson 8: Climate History and Ice Ages |
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How has climate changed in the past (ice ages) On the short time scale (within a year) Antarctica is very sensitive to changes in the seasons. This image was taken from David B. Reusch's web site at Penn State University. The animation shows sea ice concentrations over a year. Highest concentrations are shown in red and purple. Another good place to look at changes in sea ice can be found at the Discovery Channel (this one takes a while to load, but you can look at monthly changes). What is climate and how does it differ from weather? Why is it that Antarctica may be particularly sensitive to changes in climate? Antarctica is a large continent and plays a key role in both ocean circulation and temperatures. But exactly how do oceans circulate water? When water gets colder the molecules in water move closer together and become more packed or dense. If this water is more dense than the surrounding water then it will sink. As it does this warmer water from below rises and takes its place. This is called upwelling. During the process of upwelling a lot of nutrients from depths rise to the surface and when they are exposed to light, grow algae, phytoplankton and zooplankton. Fish love this phenomenon because they can eat all of these things, and humans love it too because it makes it easier to find and catch the fish. The image below illustrates the importance of Antarctica in global circulation (taken from Discovery Channel Online).
Experiment 1 You will need:
Fill one of the flasks with really cold tap water. Fill the other flask with really hot tap water and then add some dye to it. Very carefully put the cold water flask on top of the hot water flask with a piece of cardboard in the middle. When you feel you can handle the excitement pull the cardboard out as carefully as possible trying to keep both flask necks together. What happens to the dyed water? In lesson 2 you learned that a climate warming event (like the one that we are currently in) may not necessarily result in melted polar caps. So sea level change due to ice melt may not actually occur to a significant degree. However, sea level may still rise as temperature increases in ocean water result in a "swelling" of the earth's oceans. Why do you think this happens? (Remember what was mentioned before about the molecules of water when water cools.) You can conduct your own experiment to see how sea level would rise due to temperature increases. Experiment 2 You will need:
Fill the flask completely with dyed, COLD water. Cork the flask and stick the tube and the thermometer in the water. Measure the temperature of the water and record it along with the water level in a chart. Turn on the heat lamp and then record water temperature and level every 2 minutes. Can you relate this experiment to sea level rise in areas like Bangladesh and Florida? Below are three images of Florida. The first image is what Florida looked like 20,000 years ago. At that time sea level was roughly 120 metres below what it is today. The second image shows what Florida would look like with a 5 metre rise in sea level, and finally the third image shows Florida submerged as sea level rises to roughly 51 metres.    Images are from William Haxby, Adjunct Research Scientist at the Lamont-Doherty Earth Observatory |
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There is considerable debate concerning how Antarctica reacts to climate changes. Many researchers believe that Antarctica has been deglaciated (all of the ice melted) as recently as 3 million years ago. These researchers belong to a group called the non-stabilists and they believe that the Antarctic ice sheet has undergone significant melting and regrowth over time. They base these beliefs on fossil evidence found in the Transantarctic Mountains. The fossils that they've found are that of a bush that exists today in temperate environments like South America and New Zealand. Other researchers, the stabilists believe that there is considerable debate as to the age of these fossils and the sequence of events that brought them to Antarctica. 
