Lake S41, Northwest Territories 2,000 Year Chironomid Inferred Temperature MacDonald, G.M.; Porinchu, D.F.; Rolland, N.; Kremenetskii, K.V.; Kaufman, D.S. MacDonald, G.M. Porinchu, D.F. Rolland, N. Kremenetskii, K.V. Kaufman, D.S. Air Temperature Reconstruction PAGES 2k Network PAGES Arctic 2k earth science/paleoclimate/insect|paleolimnology (total head capsules,sediment,null,count,null,insect|paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (volume,wet sediment,null,milliliter,null,paleolimnology,null,null,N,used to calculate head capsule acc. rate) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Chironomus anthracinus type) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Microtendipes sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Psectrocladius semicirculatus/sordidellus) earth science/paleoclimate/climate reconstructions|insect|paleolimnology (depth,null,null,centimeter,null,climate reconstructions|insect|paleolimnology,null,null,N,null) earth 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axis,null,null,dimensionless,null,paleolimnology,null,null,N,axis 2) earth science/paleoclimate/paleolimnology (sedimentation rate,sediment,null,centimeter per year,null,paleolimnology,null,null,N,used to calculate head capsule acc. rate) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,cf. bathophila-Parakiefferiella sp.B) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Pseudosmittia sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Pentaneurini) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Procladius sp.) earth science/paleoclimate/climate reconstructions|insect|paleolimnology (surface air temperature,midge assemblage,null,degree Celsius,Jul,climate reconstructions|insect|paleolimnology,null,null,N,null) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Sergentia sp.) earth science/paleoclimate/climate reconstructions|insect|paleolimnology (lake surface temperature,midge assemblage,null,degree Celsius,summer,climate reconstructions|insect|paleolimnology,null,null,N,null) earth science/paleoclimate/climate reconstructions|insect|paleolimnology (age,null,null,year Common Era,null,climate reconstructions|insect|paleolimnology,null,null,N,null) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Polypedilum sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Corynocera oliveri) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Corynoneura sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Paracladius sp.) earth science/paleoclimate/insect|paleolimnology (total head capsules,sediment,null,count per square centimeter per year,null,insect|paleolimnology,null,null,N,Head capsule accumulation rate) earth science/paleoclimate/paleolimnology (detrended correspondence analysis axis,null,null,dimensionless,null,paleolimnology,null,null,N,axis 3) earth science/paleoclimate/paleolimnology (biogenic silica,sediment,null,milligram per gram,null,paleolimnology,null,null,N,null) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Dicrotendipes sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Tanytarsus sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Tanytarsus lugens type) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Cricotopus sp.) earth science/paleoclimate/paleolimnology (organic matter,sediment,null,percent,null,paleolimnology,null,loss on ignition,N,null) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Cladopelma sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Cladotanytarsus mancus) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Paratanytarsus sp.) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Zalutschia species A) earth science/paleoclimate/insect|paleolimnology (identified midge,null,null,percent,null,insect|paleolimnology,null,null,N,Psectrocladius septentrionalis) earth science/paleoclimate/paleolimnology (Lake S41>LATITUDE 63.718>LONGITUDE -109.318) 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 63deg 43.11'N, 109 deg 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. STUDY NOTES: Chironomid-inferred summer air and surface water temperature, plus LOI and BSi data for Lake S41, Northwest Territories, Canada. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : MacDonald, G.M. Investigator : Porinchu, D.F. Investigator : Rolland, N. Investigator : Kremenetskii, K.V. Investigator : Kaufman, D.S. 2008-11-01 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/6198 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/nwt/s41-2008.xls https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/nwt/s41-2008.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/nwt/s41-2008.xls https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/nwt/s41-2008.txt English https://www.ncdc.noaa.gov/paleo/study/6198 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/nwt/s41-2008.xls https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/canada/nwt/s41-2008.txt MacDonald, G.M., D.F. Porinchu, N. Rolland, K.V. Kremenetsky, and D.S. Kaufman2009Paleolimnological evidence of the response of the central Canadian treeline zone to radiative forcing and hemispheric patterns of temperature change over the past 2000 yearsJournal of Paleolimnology411129-14110.1007/s10933-008-9250-2 START YEAR: 1930 cal yr BP * END YEAR: -50 cal yr BP -109.318 63.718 -109.318 63.718