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Saul
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There is an unexplained mystery as to why atmosphere CO2 levels varies long term (geologically) and short term (glacial/interglacial cycle.)
Contrary to what is repeated in many blogs the glacial/interglacial cycle changes of about 90ppm to 100 ppm is not due to colder oceans being able to hold more CO2.
Simple back of the envelop analysis considering the change of solubility of CO2 in water with temperature, the maximum cooling of the ocean possible (The limit of ocean cooling is freezing the entire ocean.) and the increase in CO2 due to the reduction in the area of the planet covered by plants during the glacial period (In addition during the glacial phase, many plants die due to extremely low CO2, tropical forest are converted to grasslands and vast regions of the planet are covered by ice sheets which increases atmospheric CO2 by roughly the same amount as cooling oceans.), indicates the absolute maximum explainable due to planet cooling during the glacial period 6.5 ppm. The remaining 80 ppm to 90 ppm is drop in CO2 has no explanation.
Also puzzling is C12 significantly increases during the glacial period.
Possibly the answer to this puzzle would also explain why CO2 levels have been dropping on the planet over the last 25 million years. CO2 prior to anthropic changes, were at the lowest level in 500 million years.
Has anyone seen any papers that try to explain the long term drop in CO2?
This paper explains the mystery and proves a hypothesis that wind blown dust during the glacial period (The planet is drier when it is colder. Many plants die as a result of the low CO2 during the glacial period so desertification increases.) makes the oceans more productive and that more productive ocean (algae) reduces CO2.
The paper I provide a link to was published in 2000. A more recent paper shows the CO2 changes due not correlate with wind blown dust that increase by a factor of roughly 10 times during the glacial periods. I also have a very recent power point presentation that notes this problem is close to becoming a paradox.
http://www.up.ethz.ch/education/biogeochem_cycles/reading_list/sigman_nat_00.pdf
Glacial/interglacial variations in atmospheric carbon dioxide by Daniel M. Sigman & Edward A. Boyle
Contrary to what is repeated in many blogs the glacial/interglacial cycle changes of about 90ppm to 100 ppm is not due to colder oceans being able to hold more CO2.
Simple back of the envelop analysis considering the change of solubility of CO2 in water with temperature, the maximum cooling of the ocean possible (The limit of ocean cooling is freezing the entire ocean.) and the increase in CO2 due to the reduction in the area of the planet covered by plants during the glacial period (In addition during the glacial phase, many plants die due to extremely low CO2, tropical forest are converted to grasslands and vast regions of the planet are covered by ice sheets which increases atmospheric CO2 by roughly the same amount as cooling oceans.), indicates the absolute maximum explainable due to planet cooling during the glacial period 6.5 ppm. The remaining 80 ppm to 90 ppm is drop in CO2 has no explanation.
Also puzzling is C12 significantly increases during the glacial period.
Possibly the answer to this puzzle would also explain why CO2 levels have been dropping on the planet over the last 25 million years. CO2 prior to anthropic changes, were at the lowest level in 500 million years.
Has anyone seen any papers that try to explain the long term drop in CO2?
This paper explains the mystery and proves a hypothesis that wind blown dust during the glacial period (The planet is drier when it is colder. Many plants die as a result of the low CO2 during the glacial period so desertification increases.) makes the oceans more productive and that more productive ocean (algae) reduces CO2.
The paper I provide a link to was published in 2000. A more recent paper shows the CO2 changes due not correlate with wind blown dust that increase by a factor of roughly 10 times during the glacial periods. I also have a very recent power point presentation that notes this problem is close to becoming a paradox.
http://www.up.ethz.ch/education/biogeochem_cycles/reading_list/sigman_nat_00.pdf
Glacial/interglacial variations in atmospheric carbon dioxide by Daniel M. Sigman & Edward A. Boyle
Twenty years ago, measurements on ice cores showed that the concentration of carbon dioxide in the atmosphere was lower during ice ages than it is today. As yet, there is no broadly accepted explanation for this difference. Current investigations focus on the ocean's `biological pump', the sequestration of carbon in the ocean interior by the rain of organic carbon out of the surface ocean, and its effect on the burial of calcium carbonate in marine sediments. Some researchers surmise that the whole-ocean reservoir of algal nutrients was larger during glacial times, strengthening the biological pump at low latitudes, where these nutrients are currently limiting. Others propose that the biological pump was more efficient during glacial times because of more complete utilization of nutrients at high latitudes, where much of the nutrient supply currently goes unused. We present a version of the latter hypothesis that focuses on the open ocean surrounding Antarctica, involving both the biology and physics of that region.
An opposing effect on atmospheric CO2 to that of glacial/ interglacial temperature change is provided by the increased salinity of the glacial ocean, due to the storage of fresh water on land in extensive Northern Hemisphere ice sheets. Based on the approximately 120m depression of sea level during the last ice age18, the whole ocean was about 3% saltier than it is today. All else being constant, this increase would have reduced the solubility of CO2 in sea water and raised atmospheric CO2 by 6.5 p.p.m.v. Taking the estimated temperature and salinity effects together, we would expect the atmospheric CO2 concentration of the ice age world to have been 23.5 p.p.m.v. lower. Folding in the effect of a 500 Pg C transfer from the continents to the ocean/atmosphere system, we are left with an 8.5 p.p.m.v. decrease in CO2 (Table 1). There are uncertainties in each of these effects, but it seems that most of the 80±100 p.p.m.v. CO2 change across the last glacial/ interglacial transition must be explained by other processes. We must move on to the more complex aspects of the ocean carbon cycle.
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