Satellite data show that Greenland and Antarctica are losing mass at a rate of 283 gigatonnes per year and 145 gigatonnes per year, respectively. So how big is just one gigatonne? Central Park dimensions: 4 km meters long, 0.8km wide 1 gigatonne of ice = 1.091 km³ ice height = 1.091 km³ / (4 km * 0.8 km) = 0.3409 km = 340.9 meters A gigatonne of ice placed in the Central Park would extend 340.9 meters high.