| PALEOLIMNOLOGY |
Paleolimnological evidence of the response of the central Canadian treeline zone to radiative forcing and hemispheric patterns
of temperature change over the past 2000 years.
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MacDonald, G.M.,Porinchu, D.F.,Rolland, N.,Kremenetskii, K.V.,Kaufman, D.S. 2008 Paleolimnological evidence of the response
of the central Canadian treeline zone to radiative forcing and hemispheric patterns of temperature change over the past 2000
years. Journal of Paleolimnology
| Data Coverage |
North: 63.718 * South: 63.718 |
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West: -109.318 * East: -109.318 |
Start Year: 20 cal yr BP * End Year: 2000 cal yr BP
Data: Please Cite Data Contributors!
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Summary: Instrumental climate records from the central Canadian treeline zone
display a pattern of variation similar to general Northern Hemisphere
temperature trends. To examine whether this general correspondence
extends back beyond the instrumental record, we obtained a sediment
core from Lake S41, a small lake in the Northwest Territories
of Canada at 63°43.11'N, 109°19.07'W. A radiocarbon-based chronology
was developed for the core. The sediments were analyzed for organic-
matter content by loss-on-ignition (LOI), biogenic-silica content (BSi),
and chironomid community composition to reconstruct July air temperature
and summer water temperature. The paleolimnological records were compared
with records of atmospheric CO2 concentration, solar variability, and
hemispheric temperature variations over the past 2000 years. The results
of the analyses suggest that widely-documented long-term variations in
Northern Hemisphere temperature associated with radiative forcing,
namely the cooling following the medieval period during the Little
Ice Age (LIA), and twentieth century warming, are represented in the
central Canadian treeline zone. There is also evidence of a brief episode
of warming during the eighteenth century. As evidenced by LOI and BSi,
the twentieth century warming is typified by increased lake productivity
relative to the LIA. Depending upon the measure, the increased productivity
of the twentieth century nearly equals or exceeds that of any other period
in the past 2000 years. In contrast, the rate of chironomid head capsule
accumulation decreased and remained low during the twentieth century.
Although the chironomid-inferred temperature reconstructions indicate
cooling during the LIA, they present no evidence of greatly increased
temperatures during the twentieth century. Warming during the twentieth
century might have enhanced lake stratification, and the response of the
chironomid fauna to warming was attenuated by decreased oxygen and lower
temperatures in the hypolimnion of the more stratification-prone lake.
More Info on Paleolimnology |
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Complete XML Record: noaa-lake-6198
(Last Revised: 2009-02-11 )
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| http://www.ncdc.noaa.gov/paleo/ |
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