How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

A 380-Year History of Drought in Eastern Canada
Girardin, M-P., Tardif, J., Flannigan, M.D. and Bergeron, Y.  2004.  Multicentury reconstruction of the Canadian Drought Code from eastern Canada and its relationship with paleoclimatic indices of atmospheric circulation.  Climate Dynamics 23: 99-115.

What was done
The authors developed a 380-year reconstruction of the July monthly average of the Canadian Drought Code (CDC, a daily numerical rating of the average moisture content of deep soil organic layers in boreal conifer stands that is used to monitor forest fire danger) from 16 well replicated tree-ring chronologies from the Abitibi Plains of eastern Canada just below James Bay.

What was learned
Among other things, Girardin et al. report that "cross-continuous wavelet transformation analyses indicated coherency in the 8-16 and 17-32-year per cycle oscillation bands between the CDC reconstruction and the Pacific Decadal Oscillation prior to 1850," while "following 1850, the coherency shifted toward the North Atlantic Oscillation."

What it means
The authors say their results lead them to suggest that "the end of [the] 'Little Ice Age' over the Abitibi Plains sector corresponded to a decrease in the North Pacific decadal forcing around the 1850s," and that "this event could have been followed by an inhibition of the Arctic air outflow and an incursion of more humid air masses from the subtropical Atlantic climate sector."  In this regard, they note that several paleo-climatoogical and paleo-ecological studies have suggested that "climate in eastern Canada started to change with the end of the 'Little Ice Age' (~1850)," citing the works of Tardif and Bergeron (1997, 1999), Bergeron (1998, 2000) and Bergeron et al. (2001), while further noting that Bergeron and Archambault (1993) and Hofgaard et al. (1999) have "speculated that the poleward retreat of the Arctic air mass starting at the end of the 'Little Ice Age' contributed to the incursion of moister air masses in eastern Canada."

This substantial group of reports clearly places the "beginning of the end" of the Little Ice Age in the Abitibi Plains of Canada fully half a century before what is suggested by the Mann et al. (1998, 1999) reconstruction of Northern Hemispheric temperature over the past millennium.  Hence, it represents yet another set of studies that testifies against the validity of that faulty representation of earth's temperature history.

Bergeron, Y.  1998.  Les consequences des changements climatiques sur la frequence des feux et la composition forestiere au sud-ouest de la foret boreale quebecoise.  Geogr. Phy. Quaternary 52: 167-173.

Bergeron, Y.  2000.  Species and stand dynamics in the mixed woods of Quebec's boreal forest.  Ecology 81: 1500-1516.

Bergeron, Y. and Archambault, S.  1993.  Decreasing frequency of forest fires in the southern boreal zone of Quebec and its relation to global warming since the end of the 'Little Ice Age.'  The Holocene 3: 255-259.

Bergeron, Y., Gauthier, S., Kafka, V., Lefort, P. and Lesieur, D.  2001.  Natural fire frequency for the eastern Canadian boreal forest: consequences for sustainable forestry.  Canadian Journal of Forest Research 31: 384-391.

Hofgaard, A., Tardif, J. and Bergeron, Y.  1999.  Dendroclimatic response of Picea mariana and Pinus banksiana along a latitudinal gradient in the eastern Canadian boreal forest.  Canadian Journal of Forest Research 29: 1333-1346.

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1998.  Global-scale temperature patterns and climate forcing over the past six centuries.  Nature 392: 779-787.

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1999.  Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations.  Geophysical Research Letters 26: 759-762.

Tardif, J. and Bergeron, Y.  1997.  Ice-flood history reconstructed with tree-rings from the southern boreal forest limit, western Quebec.  The Holocene 7: 291-300.

Tardif, J. and Bergeron, Y.  1999.  Population dynamics of Fraxinus nigra in response to flood-level variations, in northwestern Quebec.  Ecological Monographs 69: 107-125.

Reviewed 24 November 2004