The article says that this is "likely accelerated by rapid human-caused global warming." Is that actually true? Does a degree or two make such a difference to something so huge?
Also, surface melt is only half the story. The base of the ice is in contact with the ocean, which is also warming. Water in contact with ice is (more or less by definition) at the freezing/melting point - if it warms, the ice melts a bit, if it cools, the water freezes. So a change in ocean temperatures can have a big effect on melt rates.
Finally, it's not enough that the shelf be in equilibrium, melt-wise. The ice is constantly thinning, as it stretches and flows under its own weight. There needs to be enough extra mass added (mostly as snow) to compensate for that, if the shelf is to remain a constant thickness.