Post by L Roebuck on Jan 22, 2007 13:56:40 GMT -5
When the mites go up…
Filed under: Climate Science Paleoclimate— group
It doesn’t seem obvious really. Going underground into caves, removing stalagmites and analysing their isotopic composition isn’t the first thing you would do to look for past climate information. But for nearly 40 years, there has been an active, and growing research community that investigates the climate records preserved in these archives. Stalagmites have recently received high profile use in climate reconstructions, for example records from China and Norway have featured in Moberg’s last millennium temperature reconstruction; in a northern hemisphere temperature reconstruction of the last 500 years and even been debated here on RealClimate. So it seems timely to review why on (or even under) earth should research go underground to look at surface climate.
To do that, we need briefly to explain how stalagmites are formed. Most simplistically, to grow a stalagmite you need water, and that water has to be saturated with carbon dioxide. Then this water drips from a cave roof, the carbon dioxide in the water will 'degas' into the atmosphere, and as part of that process calcium carbonate will form, which will form a stalagmite. Both the presence of water, and the fact that the water is saturated with carbon dioxide, can provide information about the surface climate. The water was, at one time in the past, surface rain or snow, and should contain information about that rain or snow through the composition of its isotopes. And the carbon dioxide saturation comes, not from the atmosphere, but the soil above the cave. Soil carbon dioxide concentrations are orders of magnitude greater than atmospheric, and there is a complex relationship between the concentration of soil carbon dioxide in cave drip waters, temperature and soil moisture.
Full Article
Filed under: Climate Science Paleoclimate— group
It doesn’t seem obvious really. Going underground into caves, removing stalagmites and analysing their isotopic composition isn’t the first thing you would do to look for past climate information. But for nearly 40 years, there has been an active, and growing research community that investigates the climate records preserved in these archives. Stalagmites have recently received high profile use in climate reconstructions, for example records from China and Norway have featured in Moberg’s last millennium temperature reconstruction; in a northern hemisphere temperature reconstruction of the last 500 years and even been debated here on RealClimate. So it seems timely to review why on (or even under) earth should research go underground to look at surface climate.
To do that, we need briefly to explain how stalagmites are formed. Most simplistically, to grow a stalagmite you need water, and that water has to be saturated with carbon dioxide. Then this water drips from a cave roof, the carbon dioxide in the water will 'degas' into the atmosphere, and as part of that process calcium carbonate will form, which will form a stalagmite. Both the presence of water, and the fact that the water is saturated with carbon dioxide, can provide information about the surface climate. The water was, at one time in the past, surface rain or snow, and should contain information about that rain or snow through the composition of its isotopes. And the carbon dioxide saturation comes, not from the atmosphere, but the soil above the cave. Soil carbon dioxide concentrations are orders of magnitude greater than atmospheric, and there is a complex relationship between the concentration of soil carbon dioxide in cave drip waters, temperature and soil moisture.
Full Article