Accelerating loss from major ice sheets

While the climate change deniers scoff at the poor simple souls who think that humankind might be having an influence on the climate, serious research goes on in the real world.

A letter by I. Velicogna of the Department of Earth System Science at the University of California, Irvine and the Jet Propulsion Laboratory at the California Institute of Technology, Pasadena, published in Geophysical Research Letters, 13 October 2009, demonstrates through direct observation that the rate at which the Greenland and Antarctic Ice Sheets are losing mass, through net melting of the ice, is accelerating (see abstract here).

Velicogna and his team used monthly measurements of time-variable gravity from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to determine the ice mass-loss for the Greenland and Antarctic Ice Sheets during the period between April 2002 and February 2009.

They found that during this time period the mass loss of the ice sheets is not constant, but is accelerating with time, which means that the ice sheets’ contribution to sea level rise is increasing with time. In Greenland, the mass loss increased from 137 billion tonnes per year in 2002–2003 to 286 billion tonnes per year in 2007–2009. In Antarctica the mass loss increased from 104 billion tonnes per year in 2002–2006 to 246 billion tonnes per year in 2006–2009.

This means that in both cases the rate of annual ice loss has more than doubled in less than seven years.

The body of the paper puts the best estimate of the net contribution of Antarctic and Greenland deglaciation over the past decade at 0.4 and 0.6 mm per year respectively.

Citation: Velicogna, I. (2009), Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE, Geophys. Res. Lett., 36, L19503, doi:10.1029/2009GL040222.