03602nas a2200229   4500008004100000022002500041245012200066210006900188300001400257490000800271520286600279653001203145100002203157700002103179700001603200700001603216700001703232700001503249700002303264700002003287856006503307       2019                        eng d  a2169-9003, 2169-901100aSimulated {Greenland} {Surface} {Mass} {Balance} in the {GISS} {ModelE2} {GCM}: {Role} of the {Ice} {Sheet} {Surface}0 aSimulated Greenland Surface Mass Balance in the GISS ModelE2 GCM  a750–7650 v1243 aThe rate of growth or retreat of the Greenland and Antarctic ice sheets remains a highly uncertain component of future sea level change. Here we examine the simulation of Greenland ice sheet surface mass balance (GrIS SMB) in a development branch of the ModelE2 version of the NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM). GCMs are often limited in their ability to represent SMB compared with polar region regional climate models. We compare ModelE2‐simulated GrIS SMB for present‐day (1996–2005) simulations with ﬁxed ocean conditions, at a spatial resolution of 2° latitude by 2.5° longitude ({\textasciitilde}200 km), with SMB simulated by the Modèle Atmosphérique Régionale (MAR) regional climate model (1996–2005 at a 25‐km resolution). ModelE2 SMB agrees well with MAR SMB on the whole, but there are distinct spatial patterns of differences and large differences in some SMB components. The impacts of changes to the ModelE2 surface are tested, including a subgrid‐scale representation of SMB with surface elevation classes. This has a minimal effect on ice sheet‐wide SMB but corrects local biases. Replacing ﬁxed surface albedo with satellite‐derived values and an age‐dependent scheme has a larger impact, increasing simulated melt by 60%–100%. We also ﬁnd that lower surface albedo can enhance the effects of elevation classes. Reducing ModelE2 surface roughness length to values closer to MAR reduces sublimation by {\textasciitilde}50%. Further work is required to account for meltwater refreezing in ModelE2 and to understand how differences in atmospheric processes and model resolution inﬂuence simulated SMB. Plain Language Summary Melting of the Earth's ice sheets represents a substantial contribution to global sea level rise. Global climate model simulations of Earth's climate often model the surface of ice sheets in a fairly simple way because of computational limitations. This study evaluates the representation of the Greenland ice sheet in one such global model simulation (from the NASA Goddard Institute for Space Studies general circulation model) against a regional model that simulates only the local Greenland area in a higher degree of detail. The study ﬁnds that the global model simulation of the Greenland ice sheet is sensitive to how the model represents the ice sheet surface, in particular, how it reﬂects incoming sunlight, stores and freezes liquid water, and simulates surface evaporation. Attempting to improve the simulation by dividing the ice sheet surface into additional grid cells according to surface elevation has a minor impact on the simulation. The study reveals how the representation of the Greenland ice sheet in ModelE2 might be improved to better estimate ice sheet change and the sea level response to global climate changes.10a1911-UW1 aAlexander, P., M.1 aLeGrande, A., N.1 aFischer, E.1 aTedesco, M.1 aFettweis, X.1 aKelley, M.1 aNowicki, S., M. J.1 aSchmidt, G., A.  uhttps://onlinelibrary.wiley.com/doi/abs/10.1029/2018JF00477201215nas a2200193   4500008004100000022001400041245011500055210007100170300001400241490000600255520061700261653001200878653001500890100001600905700001600921700001500937700002000952856004900972       2014                        eng d  a1991-960300aA system of conservative regridding for ice–atmosphere coupling in a {General} {Circulation} {Model} ({GCM})0 asystem of conservative regridding for ice–atmosphere coupling in  a883–9070 v73 aThe method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM) to produce high-resolution downscaled surface mass balance ﬁelds for use in one-way studies coupling atmospheres and ice ﬂow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling.10a1911-UW10aRegridding1 aFischer, R.1 aNowicki, S.1 aKelley, M.1 aSchmidt, G., A.  uhttps://www.geosci-model-dev.net/7/883/2014/