Greenland Ice Sheet solid ice discharge from 1986 through 2017

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.

Hagen Bræ: A Surging Glacier in North Greenland—35 Years of Observations

“…The outlet glaciers of North Greenland drain 40% of the Greenland Ice Sheet (Hill et al, 2017). At present, discharge from this region is low relative to other sectors due to the slow flow of its marine-terminating glaciers (Mouginot et al, 2019;Mankoff et al, 2019). North Greenland glaciers have experienced a general pattern of retreat since the early 1900s, and this trend has accelerated over the past decades (Murray et al, 2015;Hill et al, 2017Hill et al, , 2018.…”

Satellite Remote Sensing of the Greenland Ice Sheet Ablation Zone: A Review

“…As with altimetric surveys of dH/dt, the IOM reveals a complex spatial pattern of ice sheet mass loss concentrated in narrow outlet glaciers along the coastal margins, with longer term (e.g., 1990-present) mass losses concentrated in the southeast and the Jakobshavn basin in the west, and recent (post-2005) increases concentrated in the northwest [18,192,200,220,221]. In general, a small number of isolated glaciers drive the majority of D with just four (Sermeq Kujalleq, Kangerdlugssuaq, Køge Bugt, and Ikertivaq South) accounting for~50% of total D acceleration during the period 2000-2012 [18,192,222].…”

“…The IOM provides the longest record of D and, therefore, uniquely places recent MB trends in a long term context. For example, although negative SMB accounts for approximately 60% of MB for the period 1990-present, the proportion is reversed for the period 1972-2018 [192,220,221].…”

Future Evolution of Greenland's Marine‐Terminating Outlet Glaciers

“…The GrIS contains 280 fast‐flowing (>100 m/year) marine‐terminating glaciers (Figure ) with a high degree of heterogeneity across a range of parameters (Mankoff et al, ). Ice discharge from these glaciers is 500 Gt/year total, with large variations in individual glacier ice discharge associated with interglacier differences in width (1–30 km), thickness ( 100–2,000 m), terminus basal conditions (grounded, partially floating, fully floating), terminus conditions (open water, mélange—a granular matrix of icebergs, bergy bits, and sea ice—or ice shelf presence), basal substrate (bedrock, sediments, water), and other topographic controls (Enderlin et al, ; King et al, ; Mankoff et al, ). In the far north and northeast, there are relatively few outlet glaciers; most of which terminate in perennial floating ice shelves.…”

“…Submarine melting observations in Greenland are limited and, for the most part, indirect. While the total ice discharge is relatively well constrained at outlet glaciers Enderlin et al (),King et al (),Mankoff et al (), partitioning this ice discharge into calving and submarine melting is an ongoing challenge. Melt rates have been derived from satellite data for floating ice tongues (Enderlin & Howat, ; Motyka et al, ; Wilson et al, ), but these methods are not possible for the grounded or near‐grounded termini that are most prevalent around Greenland.…”