175296.fig.005
Figure 5: Fourier analysis (using Best Exact N composite algorithm) of the detrended Svalbard 1912–2010 winter (DJF) and summer (JJA) series. The amplitude of the winter signal is larger than the summer signal. The winter record is dominated by three periods of about 69.7, 25.9 and 16.7 yr length, all with amplitude greater than 1.7°C. The summer record is dominated by three periods of about 80.7, 26.4, 16.8, and 13.7 yr length, all with amplitude about 0.3°C or higher. The grey tone indicates increasing amplitude within each record. The stippled lines (white solid line for summer data) indicate peak-based critical limit significance levels. Only frequencies lower than 0.45 yr−1 are shown.