Preliminary analysis of the annual component of the polar motion over 180-year data interval

TL;DR

This study analyzes 180 years of Earth's polar motion data to identify trends in the annual component, revealing increasing amplitude and phase shifts, and correlating these with hemispheric temperature differences.

Contribution

It introduces a novel long-term analysis of the Earth's polar motion's annual component using singular spectrum analysis and Hilbert transform techniques.

Findings

Amplitude of annual oscillation increased from ~60 mas to ~90 mas.

Phase shift of approximately 45 degrees observed over 180 years.

Correlation between amplitude and hemispheric temperature differences.

Abstract

The paper presents preliminary results of studying variations in the annual component in the Earth's polar motion. For this purpose, a signal with an annual period was extracted, firstly, from the series of pole coordinates of the International Earth Rotation and Reference Systems Service (IERS), and secondly, from the combined series of Pulkovo latitude variations for 1840--2017. For this purpose, one-dimensional and multidimensional singular spectrum analysis was used. The Hilbert transform was used to calculate the change in the amplitude and phase of the annual oscillation over time. As a result, it turned out that over an interval of about 180 years, an almost monotonic increase in the amplitude of the annual oscillation from $\approx$60~mas to $\approx$90~mas and an almost monotonic phase shift of $\approx$45$^\circ$ are observed. A correlation was also found between the amplitude of the annual component and the difference in average temperatures from November to March in the northern and southern hemispheres.