Greenland Mass Trends From Airborne and Satellite Altimetry During 2011-2020

Abstract

We use satellite and airborne altimetry to estimate annual mass changes of the Greenland Ice Sheet. We estimate ice loss corresponding to a sea-level rise of 6.9 ± 0.4 mm from April 2011 to April 2020, with a highest annual ice loss rate of 1.4 mm/yr sea-level equivalent from April 2019 to April 2020. On a regional scale, our annual mass loss timeseries reveals 10-15 m/yr dynamic thickening at the terminus of Jakobshavn Isbræ from April 2016 to April 2018, followed by a return to dynamic thinning. We observe contrasting patterns of mass loss acceleration in different basins across the ice sheet and suggest that these spatiotemporal trends could be useful for calibrating and validating prognostic ice sheet models. In addition to resolving the spatial and temporal fingerprint of Greenland's recent ice loss, these mass loss grids are key for partitioning contemporary elastic vertical land motion from longer-term glacial isostatic adjustment (GIA) trends at GPS stations around the ice sheet. Our ice-loss product results in a significantly different GIA interpretation from a previous ice-loss product.

Keywords: Greenland Ice Sheet; ice dynamics; mass loss; satellite altimetry; surface mass balance; vertical land motion.

Figure 1

Effect of backscatter correction for Threshold First Maximum Retracker Algorithm (TFMRA) derived elevations shown for a 500 km² area located in Northern Greenland: (a) TFMRA elevation anomaly (black) and backscatter corrected elevation anomaly (blue) (Note: for better visibility, the blue graph was shifted by 1m); (b) backscatter anomaly; (c) Linear correlation between elevation and backscatter anomaly. The regression coefficients were used to apply the backscatter correction.

Figure 2

Effect of backscatter correction for ESA‐ICE2 derived elevations shown for a 500 km² area located in Northern Greenland: (a) ESA‐ICE2 elevation anomaly (black) and backscatter corrected elevation anomaly (blue) (Note: for better visibility the blue graph was shifted by 1m); (b) backscatter anomaly; (c) Linear correlation between elevation and backscatter anomaly. The regression coefficients were used to apply the backscatter correction.

Figure 3

Effect of leading edge correction for Threshold First Maximum Retracker Algorithm (TFMRA) derived elevations shown for a 500 km² area located in Northern Greenland: (a) TFMRA elevation anomaly (black) and leading edge corrected elevation anomaly (blue) (Note: for better visibility the blue graph was shifted by 1m); (b) leading edge width; (c) Linear correlation between elevation and leading edge width. The regression coefficients were used to apply the leading edge width correction.

Figure 4

Effect of leading edge correction for ESA‐ICE2 derived elevations shown for a 500 km² area located in Northern Greenland: (a) ESA‐ICE2 elevation anomaly (black) and leading edge corrected elevation anomaly (blue) (Note: for better visibility the blue graph was shifted by −1m); (b) leading edge width; (c) Linear correlation between elevation and leading edge width. The regression coefficients were used to apply the leading edge width correction.

Figure 5

(a) Mean surface elevation change during 2011–2020. Thickness change time series derived from CryoSat‐2 data for a single point on (b) Jakobshavn Isbrae, (c) Kangerlussuaq Glacier (KG) and (d) Helheim Glacier (HG). The location of points is shown in (a) with symbols denoting Jakobshavn Isbræ (white square), KG (blue star), and HG (black circle). The solid red curves in (b) to (d) show the best‐fitting seventh‐order polynomial.

Figure 6

Annual elevation change rates in m/yr from Airborne Topographic Mapper surveys from spring 2011 to spring 2019.

Figure 7

(a) Annual elevation change rates in m/yr from overlapping Ice, Cloud, and land Elevation Satellite‐2 (ICESat‐2) tracks during spring 2019 and spring 2020. (b) Annual elevation change rates from CryoSat‐2 during spring 2019 and spring 2020 using the method described in Section 2.1.2. (c) Difference between ICESat‐2 and CryoSat‐2 derived thinning rates.

Figure 8

(Top row) Annual (April to April) elevation change rates of the Greenland Ice Sheet from April 2011 to April 2020 from CryoSat‐2, ICESat‐2, and NASA's Airborne Topographic Mapper flights (Middle row) annual elevation change rates due to surface mass balance anomalies (Bottom row) annual elevation change rates due to ice dynamics.

Figure 9

Left axis: Cumulative anomalies in total mass (gray) in gigatons (Gt = 10¹² kg) for the period from April 2011 to April 2020 for the Greenland Ice Sheet (GIS). Right axis: Dashed blue curve denotes annual (April to April) mass change rate of the total mass of the GIS in Gt/yr. The thickness of the curves denotes the error estimates.

Figure 10

Cumulative anomalies in total mass (gray) in gigatons partitioned between surface mass balance processes (light red) and ice dynamics (purple) for (a) Drainage D8, (b) Drainage D1, (c) Drainage D2, (d) Drainage D7, (f) Drainage D3, (g) Drainage D6, (h) Drainage D5, (i) Drainage D4. The thickness of the curves denotes the error estimates. (e) Map of average elevation changes in m/yr from April 2011 to April 2020. Location names are shown for Jakobshavn Isbræ (JI), Helheim Glacier, Kangerlussuaq Glacier, Nioghalvfjerdsfjorden Glacier, the Zachariae Isstrøm, Storstrømmen Glacier, Petermann Glacier, Humboldt Glacier, and northeast Greenland ice stream.

Figure 11

Elevation change rates of Jakobshavn Isbræ in m/yr during (a) April 2011 ‐ April 2012, (b) April 2012 ‐ April 2013, (c) April 2013 ‐ April 2014, (d) April 2014 ‐ April 2015, (e) April 2015 ‐ April 2016, (f) April 2016 ‐ April 2017, (g) April 2017 ‐ April 2018, (h) April 2018 ‐ April 2019, (i) April 2019 ‐ April 2020. The black dashed line in (a) denotes the main flowline. Landsat image of Jakobshavn Isbræ from 3 July 2020 is used as background (j) Elevation change rates from April to April each year from 2011 to 2020 along the main flowline shown in (a) (k) Left axis: Cumulative anomalies in total mass (gray), dynamic loss (blue), and surface mass balance (pink) in gigatons for the time period from April 2011 to April 2020 for the Jakobshavn Isbræ drainage basin. Right axis: Cumulative mass change converted to equivalent sea‐level rise. JI drainage basin is marked as red area in the Greenland map.

Figure 12

Annual mass change rates of the Greenland Ice Sheet. The black curve shows this study. The orange curve shows IMBIE (Shepherd and Ivins, 2020), the purple curve shows Colgan et al. (2019), and the blue curve shows Simonsen et al. (2021).

Figure 13

Elevation change rates of Jakobshavn Isbræ in m/yr from Simonsen et al. (2021). The grid resolution is 5 × 5 km grid. The elevation change rates are show during (a) 2011, (b) 2012, (c) 2013, (d) 2014, (e) 2015, (f) 2016, (g) 2017, (h) 2018, (i) 2019. The background shows a Landsat Image from 3 July 2020.

Figure 14

(a) Mean elastic vertical land motion (VLM) rates in mm/yr based on 2011–2020 ice mass loss grids from this study, (b) mean elastic VLM rates based on 2011–2020 ice mass loss grids from Simonsen et al. (2021). (c) Difference between (a) and (b) in mm/yr.

Figure 15

(top) Landsat Image (from 3 July 2020) of Jakobshav Isbræ. Red dot represent location of the KAGA GPS station (botton) black errorbars denote GPS time series of cumulative vertical land motion (VLM) at KAGA corrected for glacial isostatic adjustment. Red curve denotes cumulative elastic VLM based on mass loss from this study. Blue curve denotes cumulative elastic VLM based on mass loss from Simonsen et al. (2021).