Early warning signal of abrupt change in sea level pressure based on changing spectral exponent

Abstract When a complex system crosses its critical points, abrupt change will occur with potentially catastrophic consequences. It is therefore crucial to investigate early warning signals for such transitions. Some studies show that the changing spectral exponent could serve as an early warning signal, as a dynamical system approaches its critical transition point. However, the performance of the spectral exponent may be influenced by different bifurcation types and spectral estimation techniques. We therefore first test the performance of spectral exponents obtained from different spectral estimation algorithms in several prototypical stochastic dynamical models and find that the spectral exponent based on the Burg method outperforms other existing estimators. We then employ spectral exponents for early warning of the abrupt change of sea level pressure in the North Pacific Ocean in 1976-1977. The spectral exponents obtained by the Periodogram and Burg method show a decreasing trend since 1966, which we interpret as a warning signal hindcasting the transition. While the spectral exponent estimated by the Periodogram method is sensitive to the frequency band, the spectral exponent estimated via the Burg method exhibits a consistent trend across frequency bands. This indicates the robustness of the spectral exponent obtained from the Burg method as an early warning signal of abrupt change in sea level pressure.