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Fifteen Hundred Years of South China Sea Water Temperatures

Paper Reviewed
Yan, H., Sun, L., Shao, D. and Wang, Y. 2015. Seawater temperature seasonality in the South China Sea during the late Holocene derived from high-resolution Sr/Ca ratios of Tridacna gigas. Quaternary Research 83: 298-306.

In providing some important background information for their recent publication, Yan et al. (2015) write that the marine bivalve Tridacna gigas -- which has been a prominent member of Indo-Pacific coral reef communities stretching all the way from the Eocene to the present day -- can grow to over one meter in length and live for up to 100 years. In addition, they note that T. gigas possess dense aragonite shells with daily growth lines in their inner shell layer, which makes makes them "an ideal material for high-resolution paleoclimate reconstructions," citing the work of Aharon and Chappell (1986) and Watanabe and Oba (1999) in regard to this fact.

So how did the four Chinese researchers utilize this relationship? Using high-resolution Sr/Ca ratios of modern (live-caught) and fossil (dead-collected) T. gigas shells from the South China Sea, they determined that the Medieval Climate Anomaly (better known as the Medieval Warm Period) that held sway a thousand years ago during a time when the air's CO2 concentration was approximately 280 ppm, actually had summer sea surface temperatures (SSTs) similar to those of the most recent decade, by which latter time, however, the air's CO2 concentration had risen to approximately 400 ppm. And in the even more dramatic case of winter temperatures, they report that those of the Medieval Warm Period were "much warmer" than those of the most recent decade, which finding is just the opposite of what the world's climate alarmists suggest should have been the case for such an increase in the air's CO2 concentration.

References
Aharon, P. and Chappell, J. 1986. Oxygen isotopes, sea level changes and the temperature history of a coral reef environment in New Guinea over the last 105 years. Palaeogeography, Palaeoclimatology, Palaeoecology 56: 337-379.

Watanabe, T. and Oba, T. 1999. Daily reconstruction of water temperature from oxygen isotopic ratios of a modern Tridacna shell using a freezing microtome sampling technique. Journal of Geophysical Research - Oceans 104: 20,667-20,674.

Posted 11 September 2015