  To investigate the impact of current sheet motion on the reconnection
process, we perform resistive magnetohydrodynamic (MHD) simulations of two
closely located reconnection sites which move apart from each other as
reconnection develops. This simulation develops less quickly than an otherwise
equivalent single perturbation simulation but eventually exhibits a higher
reconnection rate. The unobstructed outflow jets are faster and longer than the
outflow jets directed towards the magnetic island that forms between the two
current sheets. The X-line and flow stagnation point are located near the
trailing end of each current sheet very close to the obstructed exit. The speed
of X-line retreat ranges from ~0.02-0.06 while the speed of stagnation point
retreat ranges from ~0.03-0.07, in units of the initial upstream Alfven
velocity. Early in time, the flow stagnation point is located closer to the
center of the current sheet than the X-line, but later on the relative
positions of these two points switch. Consequently, late in time there is
significant plasma flow across the X-line in the opposite direction of X-line
retreat. Throughout the simulation, the velocity at the X-line does not equal
the velocity of the X-line. Motivated by these results, an expression for the
rate of X-line retreat is derived in terms of local parameters at the X-point.
This expression shows that X-line retreat is due to both advection by the bulk
plasma flow and diffusion of the normal component of the magnetic field.
