Figure 3. Results of wavelet analyses revealing the nonstationary fluctuations through time of the eel catch data as well as climate indices.
The left panel represents the wavelet power spectrum and the right panel indicates the global power spectrum averaged over the time series for (a) log10(eel catch), (b) winter precipitation at the eel spawning area, (c) summer NEC bifurcation, (d) summer Niño3.4 index, (e) winter QBO index, (f) winter NPGO index, (g) winter PDO index, (h) winter NPI index, (i) summer WPO index, and (j) winter sunspot numbers. The vertical axis represents period (years). The local wavelet power spectrum provides a measure of the variance distribution of the time series according to time and for each periodicity; high variability is represented by red, whereas blue indicates a weak variability. The solid black contour encloses regions of greater than 95% confidence for a red-noise process with a lag-1 coefficient, and the white dashed line area indicates the cone of influence where edge effects become important. For the global power spectrum, periods corresponding to the peaks are indicated.