The two major El Nino events correspond to a deceleration and subsequent acceleration in Earth’s rotational speed.
It is noted that NINO 1.2 SST presents only positive peaks, with little negative excursion on the downward side (in contrast to the derivative MEI index).
As such, it is not an oscillation about a neutral mean. The lag relation shows SST leading LOD changes, negating suggstions LOD is a simple causal factor.
The base line of these +ve peaks can also be related directly to LOD (rather than the rate of change shown aoove).
For details on data sources and processing see the aobve link.
MEI Multivariate ENSO Index : https://climatedataguide.ucar.edu/climate-data/multivariate-enso-index