excessive WAL activity

Just turned on WAL archiving to an S3 bucket for a small database - total size of perhaps 2-4G.  After turning on achiving, we're seeing WAL logs written to S3 at the rate of about 1G every 3 minutes.  That seems completely unreasonable given usage of the db.  I can even see that nearly nothing is happening with this:

select datname, usename, procpid, client_addr, waiting, query_start, current_query from pg_stat_activity;

Nearly every time I run that, all 20 connections have current_query = ''.  Does current_query include inserts, updates, and deletes or just select statements?

Any ideas what to look for or how to solve this?