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Reconstruction of Ob River, Russia, discharge from ring widths of floodplain trees

•Tree-ring data from the Lower Ob River Basin has a signal for river discharge.•Low growth reflects cool air temperatures, driven partly by high water levels.•December-July discharge was reconstructed from tree rings back to 1705.•Extremes in discharge on the Ob occurred prior to the start of the ga...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) 2016-12, Vol.543, p.198-207
Main Authors: Agafonov, Leonid I., Meko, David M., Panyushkina, Irina P.
Format: Article
Language:English
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Summary:•Tree-ring data from the Lower Ob River Basin has a signal for river discharge.•Low growth reflects cool air temperatures, driven partly by high water levels.•December-July discharge was reconstructed from tree rings back to 1705.•Extremes in discharge on the Ob occurred prior to the start of the gaged record.•Reconstructed Ob River discharge is characterized by large multi-decadal swings. The Ob is the third largest Eurasian river supplying heat and freshwater to the Arctic Ocean. These inputs influence water salinity, ice coverage, ocean temperatures and ocean circulation, and ultimately the global climate system. Variability of Ob River flow on long time scales is poorly understood, however, because gaged flow records are short. Eleven tree-ring width chronologies of Pinus sibirica and Larix sibirica are developed from the floodplain of the Lower Ob River, analyzed for hydroclimatic signal and applied as predictors in a regression model to reconstruct 8-month average (December-July) discharge of the Ob River at Salekhard over the interval 1705–2012 (308yrs). Correlation analysis suggests the signal for discharge comes through air temperature: high discharge and floodplain water levels favor cool growing-season air temperature, which limits tree growth for the sampled species at these high latitudes. The reconstruction model (R2=0.31, 1937–2009 calibration period) is strongly supported by cross-validation and analysis of residuals. Correlation of observed with reconstructed discharge improves with smoothing. The long-term reconstruction correlates significantly with a previous Ob River reconstruction from ring widths of trees outside the Ob River floodplain and extends that record by another century. Results suggest that large multi-decadal swings in discharge have occurred at irregular intervals, that variations in the 20th and 21st centuries have been within the envelope of natural variability of the past 3 centuries, and that discharge data for 1937–2009 underestimate both the variability and persistence of discharge in the last 3 centuries. The reconstruction gives ecologists, climatologists and water resource planners a long-term context for assessment of climate change impacts.
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2016.09.031