The Canadian singer's debut UK single sold nearly 107,000 copies during its first week on sale.
Sean Paul had to settle for the runner-up spot for the third week running with 'She Doesn't Mind', while 'Somebody That I Used to Know' - the best-selling single of the year so far - from Gotye and Kimbra climbed back up two places to three.
Nicki Minaj's 'Starships' falls one place to four, while Chris Brown tumbles to five from last week's number one with 'Turn Up the Music'.
The Script returned to the singles chart with 'The Man Who Can't Be Moved', following frontman Danny O'Donoghue's appearance on The Voice UK. It climbs 43 places to 18, having reached a high of number two back in 2008.
The only other new entry this week goes to unsigned YouTube sensation Alex Day with 'Lady Godiva' landing at 15.
Olly Murs climbs 15 spots to 13 with his latest single 'Oh My Goodness', while Beyoncé achieves a new high placing at 39 with 'End of Time'.
Source: Official Charts Company
> This week's albums chart
Watch the video for Carly Rae Jepsen's 'Call Me Maybe' below: