As the temperature of the ocean changes the isotopic composition of the ocean

As the temperature of the ocean changes the isotopic

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As the temperature of the ocean changes, the isotopic composition of the ocean will change. We can measure this by looking at fossil organisms (shells). We can measure the isotopic ratio from these shells and minerals, and therefore can find the composition of the sea water- from there we can find temperature. The measure of proportion o18/o16, gives a temperature measure. ° -Lows: ice ages. Interesting point: we’re in the middle of an ice age right now. ° -Within ice ages, there are periods of interglacial periods (temporary warming before deep freeze). ° -4 major ice ages going back 500M years. ° ° CO2 content on earth °
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° ° ° -CO2 content has been much higher in the past. ° -Because we’re in the middle of an ice age. ° -The fuss: humans are increasing it very rapidly ° - There has been time when the whole planet has been free of ice (even at poles). ° Other times, the whole earth has been covered by ice. ° ° Temperature on Planet Earth ° ° °
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° -For the last 15k years, the temperatures have been climbing, and then they go flate. Prediction: much higher. ° -The concern: we’rve had a million years of modest fluctuations, and then not its taking off because of us. ° ° CO2 Concentration vs. Temperature: ° ° ° -Tracked remarkably well. ° -Dating comes from ice precisely ° -Complete record of the deltao18 (the proportion of 18 to 16, which tracks temperature perfectly. Tracks ocean temperature. ° -They measure the CO2 content (because air gets trapped) ° ° -Reason for concern: Over 400k years, there’s been a predictable pattern (up to 280 ppm). Now CO2 concentrations are high. -If temperature is going to follow CO2, we’ll have all sorts of impacts. ° ° -Why is the CO2 oscillating? As it gets colder, CO2 dissolves more easily into the oceans. Consequently, the CO2 composition of the atmosphere is lower. As you increase temperature, CO2 is released from the ocean. The driver is temperature (for the last 400k years), when temperature is high, CO2 in the atmosphere is high, visa versa. ° ° POW camper prediction:
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° ° ° -There are 100k year intervals, they have to do with eccentricity, tilt and precession (effect of spinning the top). Sufficient to explain temperature changes. ° -prediction: warms up to a peak, drops sharply. ° -In an inter-glacial period, we gradually warm up, at some point we drop quickly. ° ° Causes of Current Global Warming CO 2 , Solar Activity or Both? ° ° -Beyond 1980, CO2 levels rise, following the temperature, but solar activity doesn’t play as much of a role (past 1970). ° ° ***What are we worrying about?
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° 1) We’re worry about the rate of change, reason: when we have global warming, ice turns to water. ° -Sea level rises, affects cities close to the ocean- just a few m increase would be catastrophic. ° -Even during interglacials, sea levels can rise up to 100m. It would wipe out all coastal towns and cities.
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  • Fall '09
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