Interannual variability of Greenland ice losses from satellite gravimetry

Using extended satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE), here we show that ice losses in southeast Greenland appear to have slowed down dramatically since late 2007, while those in the west, especially northwest Greenland show continued accelerations in recent years. Over the period April 2002 to November 2009, averaged ice loss rates in eastern Greenland (120 \textpm 31 Gt/yr) are still significantly larger than those in the west (86.3 \textpm 22 Gt/yr). However, the estimated ice loss rate from glaciers in northwest Greenland has increased from 30.9 \textpm 8 Gt/yr over the first few years (2002\textendash2005) to 128.2 \textpm 33 Gt/yr for the more recent period (2007\textendash2009), while the loss rate in southeast Greenland for the more recent period has become almost negligible, down from 109 \textpm 28 Gt/yr of just a few years ago. The rapid change in the nature of the regional ice mass in southeast and northwest Greenland, in the course of only several years, further reinforces the idea that the Greenland ice sheet mass balance is very vulnerable to regional climate conditions. The dramatic slow down of ice loss in southeast Greenland observed by GRACE provides an independent verification of similar reports from other remote sensing data. The observed significant interannual variability of Greenland ice mass change suggests that it is very challenging to quantify Greenland\textquoterights long-term ice mass change rates, and some observed apparent accelerations might simply be a reflection of the interannual variability.