Correction to: Nature Geoscience https://doi.org/10.1038/s41561-021-00720-5, published online 12 April 2021.

In the version of this Article originally published, it would not have been clear from the caption of Fig. 1 alone that the normalized concavity index is defined and calculated in ref. 7, thus the text “A similar diagram appears as Extended Data Fig. 1b of ref. 7.” has been added to the figure caption to clarify this. The online versions of the Article have been amended.