Karlberg sank birdies at the second and third to climb to ten under par but still trailed Scott by three shots after the Australian picked up a shot at the par three second to improve to 13 under.
Scott's feat was matched by Poulter, who hit his tee shot within six feet of the flag as the Englishman continued to head the pursuit of the leader on 11 under par.
Graeme McDowell was also ten under after birdieing the second to join Karlberg and Joost Luiten. The Dutchman finished his second round this morning, carding a 64, and was even through two holes of his third round.
Korean Kang Kyung-nam and Thai Prayad Marksaeng were at nine under par while Phil Mickelson and Martin Kaymer had moved into the group on eight under, both players two under for their rounds after six and five holes respectively.
Colin Montgomerie was six under but Chris Wood continued to slide down the leaderboard, the Englishman five under for the tournament after five holes of his third round.