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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME B: Data Acquisition and Processing For Scientific Knowledge and Public Awareness. : Trend and oscillations in the ice cover duration of lake mendota, wisconsin
Trend and oscillations in the ice cover duration of lake mendota, wisconsin
Author : Reza Namdar Ghanbari, Hector R. Bravo, John J. Magnuson, Randall J. Hunt, Daniel T. Feinstein, William G. Hyzer
Understanding the effect of climate variability on hydrologic variables is incomplete, and its analysis requires long time series. Lake ice cover duration data integrate effects of climate variables and have relatively long records. Singular-Spectrum Analysis (SSA) and the Multitaper Method (MTM) of spectral analysis revealed a nonlinear trend and quasi-periodic oscillations in the ice cover duration in Lake Mendota, Wisconsin. Analysis of the linearly detrended series showed significant frequencies ranging from quasi biannual to >100 years. Interannual and interdecadal signals detected are within the range of periodicity of the ENSO, PDO and NAO drivers, and sunspot activity. A smoothing procedure was used to separate low frequencies, or trend, and higher frequencies. A reconstruction of the low-pass-filtered time series that explains 95% of its variance required using 4 reconstructed components. The reconstruction showed signals centered at T = 71 and 25-27 years that could be associated with the PDO. The series showed a relatively constant trend between approximately 1895 and 1965, and a steep declining trend in the last 40 years. The reconstruction of the high frequency residuals required including 24 eigenvalues to explain 90% of the variance. The reconstruction showed signals at T = 19 and 10.5-13 years that could be associated with the PDO and NAO or sunspot activity, respectively, and signals centered at T between 2 and 7 years that could be associated with the ENSO. The results suggest a relation between the decreasing ice duration since about 1970 and the accompanying increase in Northern
Hemisphere mean annual surface temperature. This interpretation agrees with previous descriptions of observed historic changes that appear to be related to anthropogenic activity.
File Size : 569,079 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME B: Data Acquisition and Processing For Scientific Knowledge and Public Awareness.
Date Published : 01/07/2007
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