Greenland Ice Sheet solid ice discharge from 1986 through last month: Discharge

We present a 1986 through March 2020 estimate of Greenland Ice Sheet ice discharge. Our data include all discharging ice that flows faster than 100 meters per year (m yr−1) and are generated through an automatic and adaptable method, as opposed to conventional handpicked 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 12 day (d) updates to velocity. The 2010 through 2019 average ice discharge through the flux gates is ∼487±49 gigatonnes per year (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 northwest region through 2017 and in the southeast from 2017 through March 2020. As part of the journal's living archive option and our goal to make an operational product, all input data, code, and results from this study will be updated as needed (when new input data are available, as new features are added, or to fix bugs) and made available at https://doi.org/10.22008/promice/data/ice_discharge (Mankoff, 2020a) and at https://github.com/mankoff/ice_discharge (last access: 6 June 2020, Mankoff, 2020e). Mankoff, K. D., Solgaard, A., Colgan, W., Ahlstrøm, A. P., Khan, S. A., and Fausto, R. S.: Greenland Ice Sheet solid ice discharge from 1986 through March 2020, Earth Syst. Sci. Data, 12, 1367–1383, https://doi.org/10.5194/essd-12-1367-2020, 2020. Mankoff, Ken, 2020, "Greenland Ice Sheet solid ice discharge from 1986 through last month: Discharge", https://doi.org/10.22008/promice/data/ice_discharge/d/v02, GEUS Dataverse, V13本研究提供了1986年至2020年3月期间格陵兰冰盖（Greenland Ice Sheet）的冰体排泄量估算结果。本数据集涵盖所有流速超过100米/年（m yr⁻¹）的排泄冰体，其生成采用自动化且可适配的方法，而非传统的人工选取通量门（flux gates）。研究人员将通量门设置在当年冰舌末端附近，并在必要时对存在问题的冰床地形（冰厚度）数值进行估算。除采用随时间变化的年度冰厚度数据外，本时间序列还使用了流速图：其早期空间与时间覆盖度较为稀疏，后期则实现了近乎完整的空间覆盖，且流速更新频率为12天（d）一次。2010年至2019年通过通量门的平均冰体排泄量约为487±49吉吨/年（Gt yr⁻¹）。该估算10%的不确定性主要来源于冰床位置（冰厚度）的不确定性。本研究将自身结果与既往研究间约50吉吨/年的差异，归因于采用了BedMachine v3更新后的冰床地形数据。1986年至2000年期间，冰体排泄量大致保持稳定；2000年至2005年则出现显著上升，随后再次趋于平稳。但区域与单冰川的变化更为显著：多数大型冰川以及除一个区域外的所有地区近期出现排泄量下降，而这一下降趋势被2017年前的西北地区以及2017年至2020年3月的东南地区的排泄量增长所抵消。作为期刊动态存档选项的一部分，同时为实现可运维产品的研究目标，本研究的所有输入数据、代码与结果将根据需求进行更新（例如获取新输入数据、新增功能或修复漏洞时），并将在以下链接公开：https://doi.org/10.22008/promice/data/ice_discharge（Mankoff, 2020a）以及https://github.com/mankoff/ice_discharge（最后访问时间：2020年6月6日，Mankoff, 2020e）。 Mankoff, K. D., Solgaard, A., Colgan, W., Ahlstrøm, A. P., Khan, S. A., 与 Fausto, R. S.: 《1986年至2020年3月格陵兰冰盖固体冰体排泄量》，《地球系统科学数据（Earth Syst. Sci. Data）》，12卷，1367–1383页，https://doi.org/10.5194/essd-12-1367-2020, 2020. Mankoff, Ken, 2020, 《1986年至上月格陵兰冰盖固体冰体排泄量：排泄量》，https://doi.org/10.22008/promice/data/ice_discharge/d/v02，GEUS数据库（GEUS Dataverse），版本13。