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月的格陵兰冰盖（Greenland Ice Sheet）冰体排放量估算结果。本数据集涵盖所有流速高于100米/年（m yr⁻¹）的排冰水体，其生成采用自动化且可适配的方法，而非传统的人工选取冰通量闸。我们将冰通量闸设置在当年冰舌末端附近，并在必要时对存在误差的床地形（bed topography）与冰厚度（ice thickness）数值进行估算。除采用逐年动态变化的冰厚度数据外，本时间序列所使用的流速地图集，其空间与时间覆盖范围从初期的稀疏状态逐步发展至近乎全覆盖，且流速更新频率为12天（d）一次。2010年至2019年通过冰通量闸的平均冰体排放量约为487±49吉吨/年（Gt yr⁻¹）。10%的不确定性主要源于冰床位置与冰厚度的不确定性。本研究结果与既往研究间约50吉吨/年的差值，主要归因于我们采用了BedMachine v3更新后的床地形数据。1986年至2000年，冰体排放量大致保持稳定；2000年至2005年则急剧上升，之后再度趋于平稳。但区域与单冰川的变化更为显著：多数大型冰川近期呈现排放量下降趋势，除一个区域外的所有区域的排放量下降均被抵消——其中西北区域至2017年的排放量增长抵消了部分下降，而2017年至2020年3月的东南区域排放量增长同样起到了抵消作用。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（如获取新输入数据、新增功能或修复漏洞）进行更新，并可通过以下链接获取：https://doi.org/10.22008/promice/data/ice_discharge（Mankoff等，2020a）与https://github.com/mankoff/ice_discharge（最后访问时间：2020年6月6日，Mankoff等，2020e）。
曼科夫等：《1986年至2020年3月格陵兰冰盖固体冰体排放量》，《地球系统科学数据（Earth Syst. Sci. Data）》，第12卷，1367–1383页，https://doi.org/10.5194/essd-12-1367-2020，2020年。
肯·曼科夫，2020年，《1986年至上月格陵兰冰盖固体冰体排放量：排放量》，https://doi.org/10.22008/promice/data/ice_discharge/d/v02，GEUS数据库（GEUS Dataverse），版本13。