Alberta can simply keep using the Canadian dollar, with no downside.
Stated by: Commonly stated by Alberta independence advocates
Summary
A country can use another country's currency without permission, as Ecuador and Panama do with the US dollar. What it cannot do unilaterally is get a seat at the central bank, a voice in monetary policy, or a lender of last resort. When Quebec's Parti Quebecois proposed keeping the dollar, even its own leader conceded Canada's monetary policy would simply apply and a Bank of Canada seat was not guaranteed. So the claim that there is no downside is misleading: the trade-offs are real, even if their size is debated.
Evidence
Campaigning in 2014, PQ leader Pauline Marois said a sovereign Quebec would keep the loonie and seek a Bank of Canada seat, but admitted Canadian monetary policy would apply and the seat was not assured.
iPolitics (Marois on the Canadian dollar) (opens in a new tab)
Economists note that using another country's currency means no sovereign monetary policy, no ability to devalue, and no central bank backstop of your own.