Existence of a second structural break in the variance of F_ovS (ORAS5)

Ascertain whether a second structural break exists in the variance of the ORAS5‑derived F_ovS time series, as suggested by the cumulative sum of squared trend residuals analysis, and determine if this putative break reflects a real change in variability.

Background

Using the ORAS5 product for F_ovS (1958–2022), the paper applies an HP‑filter to estimate the trend and examines the cumulative sum of squared residuals to assess variance changes. A clear structural break is identified in the late 1990s, with higher variance thereafter.

The author notes a possible second change—likely a variance decrease—visible in the cumulative plot, but states it is too early to conclude whether this apparent break is real, leaving its existence as an open question.

References

However, it is too early to say whether the possible second structural break at about is real or not.

— A new indicator for the AMOC strength still gives no indication of an imminent collapse (2402.16600 - Reschenhofer, 26 Feb 2024) in Section 2 (Assessing the usefulness of the indicator F_ovS), discussion around Figure 1.c