Multiple observational evidences suggest that the Greenland Ice Sheet is losing mass since the 1990s (Lemke et al., 2007; Pritchard et al., 2009; Velicogna, 2009). The estimated annual net mass loss is more than 200 Gt in the early 21st century. The rate of this mass loss seems to be accelerating since the mid-1990s, which might be related to the greenhouse gas induced global warming (Rignot and Kanagaratnam, 2006). A few model simulations indicate that if the atmospheric greenhouse gas concentrations are stabilized at about 1000 parts per million (ppm), the whole Greenland Ice Sheet could totally melt away in about 3000 years (Ridley et al., 2005; Alley et al., 2005). Moreover, the majority of the melting would occur in the first millennium with a potential global sea level rise by more than 3 m. This means a huge amount of freshwater will flood into the North Atlantic, which potentially could significantly affect the ocean circulation there.

/Sarc