OpenMP: Do I need a critical section when I access shared variable by thread id

I am using OpenMP to parallelize a for loop. I am trying to access a C++ Armadillo vector by thread id, but I am wondering if I have to put the access in a critical section even if the different threads access disjoint areas of memory. This is my code:

#include <armadillo>
#include <omp.h>
#include <iostream>

int main()
{

        arma::mat A = arma::randu<arma::mat>(1000,700);
        arma::rowvec point = A.row(0);
        arma::vec distances = arma::zeros(omp_get_max_threads());

        #pragma omp parallel shared(A,point,distances)
        {

                arma::vec local_distances = arma::zeros(omp_get_num_threads());
                int thread_id = omp_get_thread_num();

                for(unsigned int l = 0; l < A.n_rows; l++){
                        double temp = arma::norm(A.row(l) - point,2);
                        if(temp > local_distances[thread_id])
                                local_distances[thread_id] = temp;
                }

                // Is it necessary to put a critical section here?
                #pragma omp critical 
                if(local_distances[thread_id] > distances[thread_id]){
                        distances[thread_id] = local_distances[thread_id];
                }

        }

        std::cout << distances[distances.index_max()] << std::endl;

}

Is it necessary to put read/writes to the distances vector in my case?