The flagship event is a strong invitational tournament for some of the world's top grandmasters.
Fabiano Caruana of the United States was the first to score victory in London, beating Sergey Karjakin (Russia).
Caruana is thus leading the tournament with 2.5 points, Aronian is second with 2.0 points (alongside seven other grandmasters), and Karjakin lags behind with 1.5 points so far.
The Armenian grandmaster will face France's Maxime Vachier-Lagrave in round 5 on Wednesday.
Aronian won the Stavanger-hosted Norway Chess tournament in June 2017, the Saint Louis Rapid and Blitz tournament two months later, and snatched the World Chess Cup victory in Georgia in late September. Also, the Armenian grandmaster won the fourth leg of the FIDE World Cup in Palma de Mallorca, Spain.