| PALEOLIMNOLOGY |
Late Holocene storm-trajectory changes inferred from the oxygen isotope composition of lake diatoms, south Alaska.
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Schiff, C.J.,Kaufman, D.S.,Wolfe, A.P.,Dodd, J.,Sharp, Z. 2008 Late Holocene storm-trajectory changes inferred from the oxygen
isotope composition of lake diatoms, south Alaska. Journal of Paleolimnology
| Data Coverage |
North: 60.95 * South: 60.95 |
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West: -148.15 * East: -148.15 |
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Altitude: 3 m |
Start Year: -7504 cal yr BP * End Year: 1994 cal yr BP
Data: Please Cite Data Contributors!
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Summary: 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 (60.96°N,
148.15°W; 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.
More Info on Paleolimnology |
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Complete XML Record: noaa-lake-6202
(Last Revised: 2009-02-11 )
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