Gardiner will lead the offshore wind direct investment team for GIB. He was previously senior director for energy and infrastructure at French bank BNP Paribas, where he was in charge of the bank's work on some UK offshore projects.
Last month, the bank announced plans to raise £1 billion (EUR 1.25 billion) to acquire stakes in operational offshore projects in a bid to attract long-term investors into the sector.
GIB has also announced that Karl Smith will be taking up the new role of fund managing director. Smith will be in charge of the £1 billion fund, which will operate separately from Gardiner's offshore wind direct investment team.
Smith joined GIB in 2012 and previously headed its principal equity investments in the offshore wind sector.
Since the bank was set up 18 months ago, it has invested £1.3 billion (EUR 1.6 billion) in the renewable energy sector, including the purchase of a 10% stake in the 576MW Gwynt y Môr offshore site off the coast of north Wales from developer RWE Innogy for £220 million (EUR 266 million).