ordering a 2xN matrix in Python

Question

I have a big matrix in python (in the order of 2x500), but for this example let's assume it is a 2x4 matrix:

matrix1=np.array[[2,2,3,2],
                [2,-1,-1,1]]

The matrix is a collection of points in the plain, ie:

matrix1=[[x_1,x_2,x_3,x_4],
        [y_1,y_2,y_3,y_4]]

I want to sort it in such a way that the points are ordered first by the lowest to highest value of y and then in case the y value is the same, to be sorted by x value (to say points should be going from bottom to top and in case the y value is the same from left to right in the plane). ie the matrix1 should output:

matrix1sorted=[[2,3,2,2],
               [-1,-1,1,2]]

So far I was able to sort it by the y component as follows:

import numpy as np

matrix1=np.array([[2,3,2,2],
                  [2,-1,-1,1]])
ind = np.argsort( matrix1[1,:] )
matrix1sorted=matrix1[:,ind]

which outputs:

matrix1sorted=[[3,2,2,2],
              [-1,-1,1,2]]

I have also tried something along the lines of:

matrix1=np.array([[2,3,2,2],
                  [2,-1,-1,1]])
ind = np.argsort( matrix1[1,:] )
matrix1sorted=matrix1[:,ind]
c=0
for i in range(len(matrix1[0,:])-1):
    if matrix1sorted[0,i]==matrix1sorted[0,i+1]:
        c=c+1
    else:
        ind=np.argsort( matrix1sorted[0,i:c+1] )
        matrix1sorted[:,i:c+1]=matrix1sorted[:,ind]
        c=0

Which idea was to sort first by the y component and then by the x component if the y component is the same, but I am having some trouble. Any help would be appreciated.