  Gravitational instability is thought to be one of the main drivers of angular
momentum transport in young protoplanetary discs. The disc around Elias 2-27
offers a unique example of gravitational instability at work. It is young and
massive, displaying two prominent spiral arms in dust continuum emission and
global non-axisymmetric kinematic signatures in molecular line data. In this
work, we used archival ALMA observations of $^{13}$CO line emission to measure
the efficiency of angular momentum transport in the Elias 2-27 system through
the kinematic signatures generated by gravitational instability, known as 'GI
wiggles'. Assuming the angular momentum is transported by the observed spiral
structure and leveraging previously-derived dynamical disc mass measurements,
the amount of angular momentum transport we found corresponds to an
$\alpha-$viscosity of $\alpha=0.038\pm0.018$. This value implies an accretion
rate onto the central star of
$\log_{10}\dot{M}_\star=-6.99\pm0.17\text{M}_\odot/\text{yr, which}$ reproduces
the one observed value of
$\log_{10}\dot{M}_{\star,\text{obs}}=-7.2\pm0.5\text{M}_\odot/\text{yr }$ very
well. The excellent agreement we have found serves as further proof that
gravitational instability is the main driver of angular momentum transport
acting in this system.
