What methods or strategies do you use to empower your employees to take ownership of decision-making at the frontline-- especially during unexpected disruptions?

I adhere to the less is more theory.
1) Reduce barriers to performance.
2) Set clear expectations and empower employees to contribute to those expectations.
3) Coach individually as needed.
4) Enable the workforce by providing the right level of information, eliminating the overly complex, to make informed decisions.
5) Offer consistent feedback.

There are both positive reinforcement and consequential methods.  You could leverage recognition programs for demonstrating the kind of risk culture values such as accountability of risks.  You could use more consequential methods through dashboarding/heatmapping of metrics in your reporting to force the accountability a bit.  Training on risk culture expectations might be the place to start.  Having something in performance goals around behavior such as accountability for risk and issue resolution is also an option.