2016 Update to GIS Mass Loss: McMillan et al. 2016

A recent study by McMillan et al. (2016) extends the comprehensive, inter-methodology comparison used to calculate SLR from the GIS (as discussed in the previous post). Focussing on CryoSat-2 altimetry and GRACE gravimetric measurements, this paper finds a strong correlation (R = 0.96) between mass loss from both techniques (Figure 1). Mean linear trend of these datasets is 269 ± 51 Gt yr^-1, corresponding to 0.74 ± 0.14 mm yr^-1 SLR between 2011 and 2014. This is almost identical to the previously discussed 2005-2010 estimate from Sheperd et al. (2012).

Figure 1: ‘Greenland mass evolution. Monthly evolution in ice sheet mass since 2003 from GRACE gravimetry (green) and since 2011 from CryoSat-2 altimetry and firn modelling (blue). The CryoSat-2 time series has been referenced to the GRACE data at the start of 2011. The inset shows the correspondence between GRACE and CryoSat-2 monthly estimates of mass evolution since 2011 (solid blue dots), together with a linear regression (solid blue line), the regression slope, and the Pearson correlation coefficient, R. The dashed line indicates equivalence, although the GRACE results include, additionally, mass changes of peripheral ice caps and unglaciated regions’. Caption quoted from source.

Source: McMillan et al. (2016), Figure 2.

A strength of this study is the high spatial (5 km) and temporal (monthly) resolution of the data. This enables the regions of the GIS which contribute the greatest amount to SLR to be identified with a higher degree of certainty than before. Highest mass loss is found at low latitudes, in coastal areas containing outlets glaciers. In particular, the authors observe that the South West region of the GIS is the region with the greatest contribution (approximately 41% of total ice mass loss between 2011 and 2014). The spatial pattern of mass loss measured by RA is visualised in the video below:

Source: European Space Agency 

Credit: Planetary Visions

To conclude, building on a previously developed approach, updated data corroborates IPCC estimates of SLR from the GIS. This study by McMillan et al. (2016) indicates that the linear trend of mass loss from the GIS observed  throughout the 21^st century has continued.