My return was calculated to be ~$4700, this includes deductions for RRSP contributions. After I entered my wife's tax information, my return was reduced to ~$2300. Why?

[TurboTaxSusan]

Your tax refund changes when you add your spouse's income because there are many credits that consider both spouse's income in their calculations. When you enter just your income, your joint total income may be low enough that you may get credits intended for low-income people, but once you add your spouse's income you no longer qualify for those. 

There is also the spousal amount, which is given to a person if their spouse’s net income was less than the person’s basic personal amount. If you don’t add your spouse’s income, the spousal amount will be added to your return, since zero is less that the basic personal amount. Adding the spouse’s income will remove the spousal amount if that income is too high.