![]() Since 2002, the United States (NASA) and the German (DLR) space agencies have led the Gravity Recovery And Climate Experiment (GRACE) mission. In situ gravity measurements are labor-intensive, costly to acquire, and point-based while satellite gravity data are limited in resolution due to the sensing distance. Gravity data provides direct information over ice mass changes, as the link between gravity and mass is direct and requires no calibration. (2015) used airborne altimetry to estimate glacier mass loss rate over the period 1994–2013 and found 75 ± 11 Gt/year. ![]() (2010) obtained 41.63 ± 8.6 Gt/year of glacier ice loss from Digital Elevation Models (DEM) for the period 1962–2006. (2013) found 50 ± 17 Gt/year of glacier mass loss based on several published GRACE estimates over the period 2003–2009. Over the entire Gulf Of Alaska (GOA) area, Gardner et al. (2019) estimated a total of 43 Gt of glacial mass loss over the period 2002–2015. In the Canadian Rocky Mountains, Castellazzi et al. By combining the results from these periods, they estimated an average ice mass loss rate of 16.7 ± 4.4 Gt/year. (2007) investigated glacier changes in southeast Alaska and northwest British Columbia over the period 1948–20/1987–2000, respectively. Numerous studies focused on estimating the ice mass loss over specific continents, regions, or Mountain ranges. From 120,000 glaciers available in the World Glacier Inventory, Radić and Hock (2011) estimated that the total volume loss could be as much as 21 ± 6% by 2100, leading to a total sea level rise of 124 ± 37 mm. Jin and Feng (2016) estimated the contribution of glacial melt to sea level change between 20 at 1.94 ± 0.29 mm/year. Glaciers have an important influence on sea level rise hence, their melt threatens the living environment of costal dwellings. ![]() Climate change leads to important reductions in glacial water storage. However, over the last decades, the glacier mass losses have raised concerns in and beyond the research communities. In many regions of the world, people rely on glacier meltwater for agriculture, hydropower, industries, and municipal water requirements ( Chen and Ohmura, 1990 Blanchon and Boissière, 2009). Glaciers represent 68.9% of fresh water resources worldwide. Below this threshold, errors of up to 56% are observed. ![]() Using focusing units (mascon) of ∼30,000 km 2 or larger, the focusing procedure provides reliable results with errors below 15%. Third, we show results of the three resolutions tested to focus the mass anomaly. The first studies using GRACE data published during the 2005–2008 era generally overestimated the long-term ice mass loss. This result is similar to studies using GRACE solutions from the latest releases and time-series of more than 8 years. At this scale, all solutions and distribution maps agree, showing ∼40 Gt/year of mean ice mass loss over the period 2002–2017. Second, we present the recovery of the total GRACE-derived mass change anomaly at the scale of the GOA. First, we present results from a series of simulations with synthetic data and a mix of synthetic/modeled data to validate the focusing strategy and we point out how inaccuracies arise while increasing the spatial resolution of GRACE data. Three GRACE solutions from the most common processing strategies and three ice distribution maps of resolutions ranging from 55,000 to 20,000 km 2 are used. We assess the effect of the most influential parameters such as the type of GRACE solution and the degree of heterogeneity of the distribution map over which the GRACE data is focused. In this paper, we apply an iterative constraint modeling strategy over the Gulf Of Alaska (GOA) to improve the resolution of ice loss estimates derived from GRACE. The resolution of Gravity Recovery And Climate Experiment (GRACE) Terrestrial Water Storage (TWS) change data is too low to discriminate mass variations at the scale of glaciers, small ensemble of glaciers, or icefields. 3Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina.2Land and Water, Deep Earth Imaging FSP, Commonwealth Scientific and Industrial Research Organisation, Urrbrae, SA, Australia.1Centre Eau Terre Environnement, Institut National de la Recherche Scientifique (INRS), Université du Québec, Québec City, QC, Canada.Cheick Doumbia 1*, Pascal Castellazzi 2, Alain N.
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