Greenland Ice Sheet Mass Balance Reconstruction. Part III: Marine Ice Loss and Total Mass Balance (1840-2010)

Greenland ice sheet mass loss to the marine environment occurs by some combination of iceberg calving and underwater melting (referred to here as marine ice loss, L-M). This study quantifies the relation between L-M and meltwater runoff (R) at the ice sheet scale. A theoretical basis is presented explaining how variability in R can be expected to govern much of the L-M variability over annual to decadal time scales. It is found that R enhances L-M through three processes: 1) increased glacier discharge by ice warming-softening and basal lubrication-sliding; 2) increased calving susceptibility through undercutting glacier front geometry and reducing ice integrity; and 3) increased underwater melting from forcing marine convection. Applying a semiempirical L-M f(R) parameterization to a surface mass balance reconstruction enables total ice sheet mass budget closure over the 1840-2010 period. The estimated cumulative 171-yr net ice sheet sea level contribution is 25 +/- 10 mm, the rise punctuated by periods of ice sheet net mass gain (sea level drawdown) (1893-1900, 1938-47, and 1972-98). The sea level contribution accelerated at 27.6 mm yr(-1) century(-1) over the entire reconstruction, reaching a peak sea level rise contribution of 6.1 mm decade(-1) during 2002-10.