The American Geophysical Union announced last month that they will be standardizing their reference and grammatical styles across all their publications beginning in September 2017. The organization will adopt the commonly-used APA style.
The differences between the previously-used AGU style and the newly adopted APA style primarily involve specifics of reference and citation. Parentheses will be used instead of brackets around references, and APA style adheres to more widespread hyphenation rules.
For more information about this stylistic shift, please refer to this article.