GIGNAC, L. DENNIS*, LINDA A. HALSEY, AND DALE H. VITT. L. Dennis Gignac, Faculte Saint-Jean, University of Alberta, Edmonton, AB T6G 2E1, L.A. Halsey and D.H. Vitt, Biological Sciences, University of Alberta, Edmonton, AB T6G 2E1. - Evaluating GCM outputs for 0ka BP and 6ka BP using the distribution of Sphagnum-dominated peatlands in North America.
A model was constructed that projects the presence or absence of
Sphagnum-dominated peatlands in climatic space using two variables:
mean annual temperature (MAT) and mean annual total precipitation
(MATP). The climatic variables in the model were then coupled to those
measured at weather stations in order to plot the projected
distribution of Sphagnum-dominated peatlands in North America. The
projected distribution was then compared to the current bog and poor
fen distribution that was reconstructed from the abundance of Sphagnum
spores in cores obtained from lake sediments. That comparison
revealed that the Sphagnum-dominated Peatland Distribution Model
(SPDM) had an accuracy of 90%.
The the climatic variables in
the SPDM were then coupled with the reconstruction of the current
climate (0ka BP) produced by two General Circulation Models (GCMs).
The resulting geographic projections were then compared to the current
distribution of Sphagnum-dominated peatlands. Results indicated that
the accuracy of the Canadian Climate Centers (CCC) GCM output varied
between 77 and 82% while the General Fluid Dynamics Laboratory (GFDL)
GCM had an accuracy of 56%. Errors for both GCMs were mostly located
in areas immediately east of the Rocky Mountains and in north-eastern
North America. The SPDM was then coupled with the GCM
reconstructions for the climate at 6ka BP and the resulting geographic
distribution was compared to the distribution of Sphagnum-dominated
peatlands that was reconstructed from Sphagnum spore counts in lake
sediments for the same time period. Results indicated that the CCC
output had an accuracy of 70% while the GFDL output was 45% accurate.
Errors produced by the changes in climate between 6ka BP and 0ka BP
(anomalies) projected by both GCMs were also evaluated. The accuracy
for the CCC GCM anomalies was 69% while the GFDL anomalies accuracy
was equal to 40%.
Key words: bogs, climate reconstruction, General Circulation Models, poor fens, Spahgnumspores, Sphagnum abundance