The acquisition agreement allows OX2 to commence construction of the project before handing it to Ikea once it is completed in 2017.
The site in Ajos harbour currently has ten WinWind 3MW turbines. Eight of the turbines are installed on man-made islands, with two on the mainland.
OX2's repowered project will comprise 13 Siemens turbines. Eight of the manufacturer's 3.2MW turbines with 113-metre rotors will replace the machines on the artificial islands in the harbour.
The two onshore turbines will be replaced by five Siemens 3.3MW turbines with 130-metre rotors.
Following the completion of the project, OX2 will continue to operate it for Ikea.
"The new wind farm will mean we produce more renewable energy than all the energy we use in our buildings in Finland," said IKEA Finland Country manager Lars Midttun.
In June 2015, the retailer pledged to invest a further €500 million in wind projects by 2020, adding to the €1.5 billion it had already spent on renewable energy since 2009.
It is aiming to become "energy independent" by owning as much renewable energy capacity as it consumes.