Abstract
Abstract. We present a 1986 through 2017 estimate of Greenland Ice Sheet ice discharge. Our data include all discharging ice that flows faster than 100 m yr−1 and are generated through an automatic and adaptable method, as opposed to conventional hand-picked gates. We position gates near the present-year termini and estimate problematic bed topography (ice thickness) values where necessary. In addition to using annual time-varying ice thickness, our time series uses velocity maps that begin with sparse spatial and temporal coverage and end with near-complete spatial coverage and 6 d updates to velocity. The 2010 through 2017 average ice discharge through the flux gates is ∼488±49 Gt yr−1. The 10 % uncertainty stems primarily from uncertain ice bed location (ice thickness). We attribute the ∼50 Gt yr−1 differences among our results and previous studies to our use of updated bed topography from BedMachine v3. Discharge is approximately steady from 1986 to 2000, increases sharply from 2000 to 2005, and then is approximately steady again. However, regional and glacier variability is more pronounced, with recent decreases at most major glaciers and in all but one region offset by increases in the NW (northwestern) region. As part of the journal's living archive option, all input data, code, and results from this study will be updated when new input data are accessible and made freely available at https://doi.org/10.22008/promice/data/ice_discharge.
Highlights
The mass of the Greenland Ice Sheet is decreasing (e.g., Fettweis et al, 2017; van den Broeke et al, 2017; Wiese et al, 2016; Khan et al, 2016)
Different ice discharge estimates among studies likely stem from three categories: (1) changes in true discharge, (2) different input data, and (3) different assumptions and methods used to analyze data
We have presented a novel dataset of flux gates and a 1986 through 2017 glacier-scale ice discharge estimate for the Greenland Ice Sheet
Summary
The mass of the Greenland Ice Sheet is decreasing (e.g., Fettweis et al, 2017; van den Broeke et al, 2017; Wiese et al, 2016; Khan et al, 2016). Greenland’s total ice loss can be estimated through a variety of independent methods, for example “direct” mass change estimates from GRACE (Wiese et al, 2016) or by using satellite altimetry to estimate surface elevation change, which is converted into mass change (using a firn model, e.g., Khan et al, 2016). As well as the attribution of this loss (SMB or D), is critical to understanding the process-level response of the Greenland Ice Sheet to climate change and improving models of future ice-sheet changes and associated sea-level rise (Moon et al, 2018)
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