  We combine two point velocity and position data from surface drifter
observations in the Benguela upwelling region off the coast of Namibia. The
compensated third order longitudinal velocity structure function
$\left\langle{\Delta u_{\ell}^{\rm 3}}\right\rangle/s$ shows a positive plateau
for inertial separations $s$ roughly between $9~\rm{km}$ and $120~\rm{km}$
revealing an inverse energy cascade with energy transfer rate
$\varepsilon\simeq 1.2 \pm 0.1 \cdot 10^{-7} m^3/s^2$. Deviations from
Gaussianity of the corresponding probability distribution $P(\Delta u_{\ell}
|s)$ of two-point velocity increments $\Delta u_{\ell}$ for given pair
separation $s$ show up in the n$^{th}$ antisymetric structure functions
$S_{-}^{(n)}(r)=\int u^n(P(u)-P(-u)d u$, which scale in agreement with
Kolmogorov's prediction, $S_{-}^{(n)}(r)\sim r^{(n/3)}$, for $n=2,4,6$. The
combination of $\varepsilon$ with Richardson dispersion
  $\left\langle s^2(t)\right\rangle=g\varepsilon t^3$, where $\left\langle
s^2(t)\right\rangle$ is mean squared pair separation at time $ t$, reveals a
Richardson-Obhukov constant of $g\simeq 0.11\pm 0.03$.
