Forfjorddalen, Norway 1000 Year Tree Ring d13C Cloud Cover Reconstruction Young, G.H.F.; McCarroll, D.; Loader, N.J.; Gagen, M.; Kirchhefer, A.J.; Demmler, J.C. Young, G.H.F. McCarroll, D. Loader, N.J. Gagen, M. Kirchhefer, A.J. Demmler, J.C. Arctic Oscillation (AO) Little Ice Age (LIA) Other Hydroclimate Reconstruction PISY Pinus sylvestris L. Scots pine Scotch pine earth science/paleoclimate/tree ring (delta 13C,latewood alpha cellulose,null,per mil VPDB,null,tree ring,composited|corrected,isotope ratio mass spectrometry,N,corrected for the decrease in atmospheric δ13C values due to the rise in CO2 caused by fossil fuel combustion since the beginning of the industrialization) earth science/paleoclimate/tree ring (number of samples,null,null,count,null,tree ring,null,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (cloud cover,null,null,percent,null,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (cloud cover,null,null,percent,null,climate reconstructions|tree ring,filtered,null,N,20-year filter) earth science/paleoclimate/tree ring (age,null,null,year Common Era,null,tree ring,null,null,N,null) earth science/paleoclimate/tree ring (delta 13C,latewood alpha cellulose,one standard deviation,per mil VPDB,null,tree ring,composited|corrected,isotope ratio mass spectrometry,N,corrected for the decrease in atmospheric δ13C values due to the rise in CO2 caused by fossil fuel combustion since the beginning of the industrialization) earth science/paleoclimate/tree-ring (Forfjorddalen13C>LATITUDE 68.6>LONGITUDE 15.7333) Cloud cover currently represents the single greatest source of uncertainty in General Circulation Models. Stable carbon isotope ratios (d13C) from tree-rings, in areas of low moisture stress, are likely to be primarily controlled by photosynthetically active radiation (PAR), and therefore should provide a proxy record for cloud cover or sunshine; indeed this association has previously been demonstrated experimentally for Scots pine in Fennoscandia, with sunlight explaining ca 90% of the variance in photosynthesis and temperature only ca 4%. We present a statistically verifiable 1011-year reconstruction of cloud cover from a well replicated, annually-resolved d13C record from Forfjord in coastal northwestern Norway. This reconstruction exhibits considerable variability in cloud cover over the past millennium, including extended sunny periods during the cool seventeenth and eighteenth centuries and warm cloudy periods during the eleventh, early fifteenth and twentieth centuries. We find that while a generally positive relationship persists between sunshine and temperature at high-frequency, at lower (multi-decadal) frequencies the relationship is more often a negative one, with cool periods being sunny (most notably the Little Ice Age period from 1600 to 1750 CE) and warm periods more cloudy (e.g. the mediaeval and the twentieth century). We conclude that these long-term changes may be caused by changes in the dominant circulation mode, likely to be associated with the Arctic Oscillation. There is also strong circumstantial evidence that prolonged periods of high summer cloud cover, with low PAR and probably high precipitation, may be in part responsible for major European famines caused by crop failures. STUDY NOTES: A 1010-year stable carbon isotope chronology from Forfjorddalen on the Vesterålen archipelago of northwestern Norway was produced from Pinus sylvestris L. (Scots Pine). Individual isotope series were corrected for changes in, the isotopic ratio and concentration of, atmospheric CO2 over the industrial period (since AD1850). The mean isotope series was calibrated against observed percentage cloud cover from Tromsø, over the period AD1890-2001 (R2, 0.46). The mean isotope series was then scaled to Tromsø cloud cover to produce a 1010-year reconstruction of percentage cloud cover. See Young et al. (2010; 2012) for full details. Forfjorddalen, Forfjord, Vesterålen, Northern Norway: 68°48'N, 15°44'E IITRDB005 NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Young, G.H.F. Investigator : McCarroll, D. Investigator : Loader, N.J. Investigator : Gagen, M. Investigator : Kirchhefer, A.J. Investigator : Demmler, J.C. 2012-07-31 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/13179 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/norway/forfjorddalen2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/norway/forfjorddalen2012.xls https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/norway/forfjorddalen2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/norway/forfjorddalen2012.xls English https://www.ncdc.noaa.gov/paleo/study/13179 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/norway/forfjorddalen2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/isotope/europe/norway/forfjorddalen2012.xls Young, G.H.F., D. McCarroll, N.J. Loader, M. Gagen, A.J. Kirchhefer, and J.C. Demmler. 2012. Changes in atmospheric circulation and the Arctic Oscillation preserved within a millennial length reconstruction of summer cloud cover from northern Fennoscandia. Climate Dynamics, Vol. 39, pp. 495-507. DOI:10.1007/s00382-011-1246-3. START YEAR: 990 AD * END YEAR: 2001 AD 15.7333 68.6 15.7333 68.6