If average depth of an ocean is 4000 m and the bulk modulus of water is $2 \times 10^9 \mathrm{Nm}^{-2}$, then fractional compression $\frac{\Delta \mathrm{V}}{\mathrm{V}}$ of water at the bottom of ocean is $\alpha \times 10^{-2}$. The value of $\alpha$ is (Given, $\mathrm{g}=10 \mathrm{~ms}^{-2}, \rho= 1000 \mathrm{~kg} \mathrm{~m}^{-3}$ )