Satellite data has been collected since 2003. The loss in 2019 was double the annual average of 255 billion tonnes since then. Almost that amount was lost in July 2019 alone.
Scientists knew that the loss of ice in Greenland had accelerated rapidly in recent decades and that there had been high rates of melt in 2019. But satellite data explains new snowfall and makes it possible to calculate the net loss. The researchers said the scale of the loss in 2019 was shocking and was probably the largest in centuries, if not millennia.