"The spatially averaged increase is 5.4 cm per year over the study area, when corrected for post-Ice Age uplift of the bedrock beneath the ice sheet. These results are remarkable because they are in contrast to previous scientific findings of balance in Greenland's high-elevation ice."
A net increase in mass.
The trend below 1500 metres however does not include the steeply-sloping marginal areas where current altimeter data are unusable.
This might mean that the loss of 2cm/yr in the below 1500 meters areas the satellite can measure, along with the marginal areas, roughly balances the 6.0cm/yr gain in the interior (above 1500 meters).
Hence the article's "no consensus" and "need for further data". Or in the words of the study's author:
"There is clearly a need for continued monitoring using new satellite altimeters and other observations, together with numerical models to calculate the Greenland Ice Sheet mass budget," Johannessen added.