  We present a new method to study the Nernst effect and diamagetism of an
extreme type-II superconductor dominated by phase fluctuations. We work
directly with vortex variables and our method allows us to tune vortex
parameters (e.g., core energy and number of vortex species). We find that
diamagnetic response and transverse thermoelectric conductivity ($\alpha_{xy}$)
persist well above the Kosterlitz-Thouless transition temperature, and become
more pronounced as the vortex core energy is increased. However, they
\textit{weaken} as the number of internal vortex states are increased. We find
that $\alpha_{xy}$ closely tracks the magnetization $(-M/T)$ over a wide range
of parameters.
