The 25-year-old signed a four-year contract on Monday, keeping him at Arsenal until 2024 after the club agreed a deal with Dijon worth just over £1million.
Though Arsenal only officially announced the deal on Monday evening, the pictures released show Runarsson has already been out training at the club's London Colney base.
Runarsson has been pictured working alongside goalkeeping coach Inaki Cana, who proved instrumental in the player's decision to join Arsenal after the pair worked together at FC Nordsjaelland in Denmark.
“We’re very pleased to welcome Alex to our squad," Edu told the club's website.
"We have been monitoring him for some time and from the analysis, he has strong attributes that we look for in a goalkeeper and as a person.”
Arteta also expressed his delight with the addition, adding: “We want to create healthy competition for places and we look forward to seeing Alex bring further depth to the goalkeeping position.”
Scroll through the gallery above to see the first pictures of Runarsson in Arsenal colours...