Okay, I found it.
The resistivity of copper at 20deg C is 16.78nOhm-m.
And the resistivity of copper increases at 0.393 percent per degree C.
So, the resistivity at 273 Kelvin = 0 degrees C is
16.78nOhm-m*(1-0.00393*20) = 15.461092nOhm-m
And your final answer is:
Resistance(nOhms) = 15.461092nOhm-m * 1000m / 10e-6m^2 = 1546109200nOhms = 1.5461092 Ohms.
Now just to reassure myself, I looked in standard copper wire resistance tables. 10mm^2 is between the 8AWG and 6AWG. The resistance of 1000m of 8 and 6AWG is 2.1Ohms and 1.32Ohms, respectively. So, this works.