How does rising atmospheric CO2 affect marine organisms?

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The Medieval Warm Period in Southern Greenland
Norgaard-Pedersen, N. and Mikkelsen, N. 2009. 8000 year marine record of climate variability and fjord dynamics from Southern Greenland. Marine Geology 264: 177-189.

What was done
Working with a sediment core retrieved in August 2006 from the deepest basin of Narsaq Sound (6056.200'N, 4609.300'W) in southern Greenland, the authors measured and analyzed several properties of the materials thus obtained from which they were able to infer various "glacio-marine environmental and climatic changes" that had occurred over the prior 8,000 years.

What was learned
Norgaard-Pedersen and Mikkelsen report that their coarse fraction and magnetic susceptibility data, along with their ice-rafted debris data, reveal the existence of two periods (2.3-1.5 ka and 1.2-0.8 ka) that "appear to coincide roughly with the 'Medieval Warm Period' and 'Roman Warm Period'," while they identify the colder period that followed the Medieval Warm Period as the Little Ice Age and the colder period that preceded it as the Dark Ages Cold Period.

What it means
Citing the works of Dahl-Jensen et al. (1998), Andresen et al. (2004), Jensen et al. (2004) and Lassen et al. (2004), the two Danish scientists say that "the cold and warm periods identified in [those researchers' studies] appear to be more or less synchronous to the inferred cold and warm periods observed in the Narsaq Sound record," providing ever more evidence for the reality of the naturally-occurring phenomenon that governs this millennial-scale oscillation of climate that has now been identified throughout the world (see the Interactive Map and Time Domain Plot of our Medieval Warm Period Project for a panoramic view of where (and when) this particular warm node of the oscillation has been observed).

Andresen, C.S., Bjorck, S., Bennike, O. and Bond, G. 2004. Holocene climate changes in southern Greenland: evidence from lake sediments. Journal of Quaternary Science 19: 783-793.

Dahl-Jensen, D., Mosegaard, K, Gundestrup, N., Clew, G.D., Johnsen, S.J., Hansen, A.W. and Balling, N. 1998. Past temperatures directly from the Greenland ice sheet. Science 282: 268-271.

Jensen, K.G., Kuijpers, A., Koc, N. and Heinemeier, J. 2004. Diatom evidence of hydrographic changes and ice conditions in Igaliku Fjord, South Greenland, during the past 1500 years. The Holocene 14: 152-164.

Lassen, S.J., Kuijpers, A., Kunzendorf, H., Hoffmann-Wieck, G., Mikkelsen, N. and Konradi, P. 2004. Late Holocene Atlantic bottom water variability in Igaliku Fjord, South Greenland, reconstructed from foraminifera faunas. The Holocene 14: 165-171.

Reviewed 18 November 2009