This has been happening in increasing frequency. To get the accounts merged, the user will need to request it. I left the following comment under the most recent post from this person:
Hey AntarcticGorilla, the creation of multiple questions does lead to some problems, so if you're planning to continue to participate, I encourage you to register and then see these instructions on how to request an account mergesee these instructions on how to request an account merge. When contacting the team, you may want to reference this meta post as one of our users was kind enough to put together links to all your profiles. :) Good luck!
Just in case this person loses access to the most recent account, please feel free to reuse this or a variation of this comment if another question pops up from yet another new account.