Improving the ability of regional climate models (RCMs) and ice sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland Ice Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-Annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for mass change are less well understood and modeled, and could potentially play an important role in future GrIS mass change. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the January 2003-December 2012 period using a "mascon" approach, with a nominal spatial resolution of 100ĝ€km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the Ice Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of ĝ'178.9ĝ€±ĝ€4.4 and ĝ'239.4ĝ€±ĝ€7.7ĝ€Gtĝ€yrĝ'1 respectively) in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000ĝ€m in elevation, where the majority of recent GrIS mass loss is occurring. On an ice-sheet-wide scale, the timing of the modeled seasonal cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-ice-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or processes not accounted for by models related to ice dynamics or hydrology, may lead to the observed differences. This highlights the need for further evaluation of modeled processes at regional and seasonal scales, and further study of ice sheet processes not accounted for, such as the role of subglacial hydrology in variations in glacial flow.
Graduate Center of the City University of New York, 365 5th Ave, New York, NY, United States; City College of New York, City University of New York, 160 Convent Ave, New York, NY, United States; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY, United States; Lamont Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, United States; Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, CA, United States; Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive MS, Pasadena, CA, United States; Planetary Geodynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, United States; Laboratory of Climatology, Department of Geography, University of Liège, no. 2 Allé du 6 Aout, Liège, Belgium
Recommended Citation:
Alexander P,M,, Tedesco M,et al. Greenland Ice Sheet seasonal and spatial mass variability from model simulations and GRACE (2003-2012)[J]. Cryosphere,2016-01-01,10(3)