Fig. 1

Secular variation (SV) of the East component Y at different observatory locations. Yellow dots represent the SV (with its error bars) computed from the monthly mean observatory data. See the locations of the selected observatories in Fig. 3. Red and blue curves are the SV estimation at the respective location given by the CHAOS-7.7 model (Finlay et al. 2020). Note that after August 2020 the changes in the curves (blue lines) from CHAOS-7.7 are likely affected by the model regularization instead of the data (see Sect. 3 for more details)