I think I have found a bug with the IWarehouseRepository.

Currently there is no way to clear the cache.

If you want to get a list of warehouses:

            //var warehouseRepository = ServiceLocator.Current.GetInstance();
            //return warehouseRepository.List();

This will get cached items.

Decompiling the source code: WarehouseRepositoryDatabase it clearly gets from the cache:

List warehouseList1 = this._cache.Get("EP:Commerce:WL") as List;

There is no public method on the interface to clear the cache or refresh it.