Is this a real result about the Greenland ice sheet?

A new study purports to show that summer temperatures exert less of an influence on Greenland ice sheet melting that previously believed. This result is based on measurements of ice flow for six outlet glaciers. I think that this is a small subset, and I also think that overall ice loss has to be evaluated via satellite or aircraft survey in addition to changing any general view of the threat to the ice sheet from warming.

Greenland ice sheet a complex mystery

Shepherd and his team used satellite observations of six landlocked glaciers in south-west Greenland, acquired by the European Space Agency, to study how ice flow developes in years of markedly different melting.

Despite the fact that the initial speed up of ice melting was similar in all years, slowdown occurred soonest in years which were warmer than others, suggesting that these years of abundance triggers an early switch in the plumbing at the base of the ice, causing a pressure drop that slows down the ice speeds, behaviour that is similar to mountain glaciers, which sees summertime speed up of ice reduce once the melt-water from the glaciers can drain efficiently.

My question: what about glaciers that drain to the sea, like the huge Jakobshavn?