Mica Lake, Alaska 9,000 Year Diatom Isotope Data Schiff, C.J.; Kaufman, D.S.; Wolfe, A.P.; Dodd, J.; Sharp, Z. Schiff, C.J. Kaufman, D.S. Wolfe, A.P. Dodd, J. Sharp, Z. PAGES 2k Network PAGES Arctic 2k earth science/paleoclimate/paleolimnology (delta 18O,diatom,null,per mil,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (depth,null,null,meter,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (biogenic silica,sediment,null,percent,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (organic matter,sediment,null,percent,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (age,null,null,calendar year before present,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (Mica Lake>LATITUDE 60.95>LONGITUDE -148.15) The oxygen isotope ratios of diatoms (d18Odiatom), and the oxygen and hydrogen isotope ratios of lake water (dW) of lakes in south Alaska provide insight into past changes in atmospheric circulation. Lake water was collected from 31 lakes along an elevation transect and diatoms were isolated from lake sediment from one lake (Mica Lake) in south Alaska. In general, dW values from coastal lakes overlap the global meteoric water line (GMWL). dW values from interior lakes do not lie on the GMWL; they fall on a local evaporation line trajectory suggesting source isotopes are depleted with respect to maritime lakes. Sediment cores were recovered from 58 m depth in Mica Lake (60.96N, 148.15W; 100 m asl), an evaporation-insensitive lake in the western Prince William Sound. Thirteen calibrated 14C ages on terrestrial macrofossil samples were used to construct an age-depth model for core MC-2, which spans 9910 cal years. Diatoms from 46, 0.5-cm-thick samples were isolated and analyzed for their oxygen isotope ratios. The analyses employed a newly designed, stepwise fluorination technique, which uses a CO2 laser-ablation system, coupled to a mass spectrometer, and has an external reproducibility of 0.2%. d18Odiatom values from Mica Lake sediment range between 25.2 and 29.8%. d18Odiatom values are relatively uniform between 9.6 and 2.6 ka, but exhibit a four-fold increase in variability since 2.6 ka. High-resolution sampling and analyses of the top 100 cm of our lake cores suggest large climate variability during the last 2000 years. The 20th century shows a +4.0% increase of d18Odiatom values. Shifts of d18Odiatom values are likely not related to changes in diatom taxa or dissolution effects. Late Holocene excursions to lower d18Odiatom values suggest a reduction of south-to-north storm trajectories delivered by meridional flow, which likely corresponds to prolonged intervals when the Aleutian Low pressure system weakened. Comparisons with isotope records of precipitation (dP) from the region support the storm-track hypothesis, and add to evidence for variability in North Pacific atmospheric circulation during the Holocene. STUDY NOTES: d18O diatom, biogenic silica, and organic matter from Mica Lake, Alaska, USA NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Schiff, C.J. Investigator : Kaufman, D.S. Investigator : Wolfe, A.P. Investigator : Dodd, J. Investigator : Sharp, Z. 2008-11-01 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/6202 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/mica2008.xls https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/mica2008.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/mica2008.xls https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/mica2008.txt English https://www.ncdc.noaa.gov/paleo/study/6202 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/mica2008.xls https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/mica2008.txt Schiff, C.J., D.S. Kaufman, A.P. Wolfe, J. Dodd, and Z. Sharp2009Late Holocene storm-trajectory changes inferred from the oxygen isotope composition of lake diatoms, south AlaskaJournal of Paleolimnology411189-20810.1007/s10933-008-9261-z START YEAR: 9454 cal yr BP * END YEAR: -44 cal yr BP -148.15 60.95 -148.15 60.95