He went on to make 22 appearances for the Black Cats before joining Spurs. But he has been unable to break into the first-team picture at White Hart Lane and spent loan spells at Luton Town and Leicester City last season.
"I'm pleased that the board has backed us in recent weeks," said Ward. "We've brought Ben in as well as Graham Kavanagh and Jennison Myrie-Williams and it shows everyone at the football club is trying to rectify the position we're in."
Alnwick's arrival has increased speculation over the future of Carlisle's second-choice goalkeeper Chris Howarth, yet to make a first-team appearance for the club.
"I'll speak to Chris about the situation," said Ward. "It wasn't a question of going out to get a new goalkeeper in.
"But the opportunity to bring Ben Alnwick in came up and was one I felt I had to take."
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