Flood/drought variability in the Yangtze Delta and association with the climatic changes from the Guliya ice core: A wavelet approach

Correlativity between flood/drought variability in the Yangtze Delta and temperature/precipitation changes reconstructed from the oxygen isotope (δ18O/δ16O) and ice accumulation were detected using continuous wavelet transform, cross-wavelet and squared-wavelet coherence approaches. Research results indicate that: (1) significant wavelet variance fluctuations occurred during 1115–1315 AD and 1415–1715 AD; in terms of larger time scales, the significant wavelet variance fluctuations can be identified during 1115–1315 AD and 1715–1865 AD; (2) cross-wavelet analysis and wavelet coherence analysis demonstrate concurrent correlations between flood/drought variability in the Yangtze Delta and temperature changes reconstructed from the Guliya ice core, but are varying over time and in different time scales. Generally, relatively stable relations are found in the larger time scales and ambiguous ones in the shorter time scales; (3) in-phase relations in 4–8-year time scales and anti-phase relations in 8–16-year time scales are identified between flood/drought variability in the Yangtze Delta and temperature changes reconstructed from the Guliya ice core. The correlativity between flood/drought changes and precipitation changes reconstructed from the Guliya ice core is relatively weak and ambiguous without obvious changing patterns.