The 21-year-old, who enjoyed spells at Luton and Leicester last season, moves to Brunton Park on another temporary deal in a bid to get some regular action
And Carlisle boss John Ward was delighted with the arrangement as he told the United website: "He's a keeper that's known to this part of the world from his time at Sunderland, prior to his move down to Tottenham.
"With the change of management and the influx of foreign keepers at White Hart Lane he has been on the fringes of their first team, but he has had some good loan spells whilst he has been there.
"It's a position that we feel needs to be freshened up, so we've spoken to Tottenham and agreed to get him up here for a month."
Ward added: "Alnwick is a good keeper and he is very keen to get himself some first team football again. He played for the Tottenham reserves up in Glasgow earlier this week, so he's up to speed and raring to go.
"As it happens he was in Scotland when we asked to do the loan, so he was able to join us last night ahead of training this morning."