When an organization is going through tremendous change at top level. How can HR keep its workforce engaged and minimize rumors?

They should be made aware of the changes

HR should be transparent about the changes happening in any Org. Have the employees know what changes the Org. will go through and which all Dept. will be affected with it. And also before the Org. Change takes place the HR Team should let know all the employees so that rumors can be avoided

When an organization is going through tremendous change at top level, HR can keep its workforce engaged and minimize rumors by:

Communication effectively, that is, keeping the employees informed on the actual happenings in the organization so that they will not hear it from outsider and begin to peddle rumors around.

Regular meeting should be held  carry all staff members along.

HR should take the employees into confidence and share the real reason behind the change to curb the rumors. For more satisfaction of the employees, they should share the road-map of the company as a result of these high level changes. They should communicate on how the new management will take the company to next level and how this change will make the lives of employees better.