Vertical and horizontal surface displacements near Jakobshavn Isbræ driven by melt‐induced and dynamic ice loss

Nielsen, Karina; Khan, Shfaqat Abbas; Spada, Giorgio; Wahr, John; Bevis, Michael; Liu, Lin; Dam, Tonie van

doi:10.1002/jgrb.50145

Cited by 35 publications

(33 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The processes that concentrate long-term dynamic mass loss on the outlet glaciers also influence the seasonal mass-balance cycle, as meltwater and runoff can affect flow velocities (Andersen et al, 2010;Sole et al, 2011;Joughin et al, 2008), submarine melt (Motyka et al, 2003;Jenkins, 2011), and iceberg calving (O'Leary and Christoffersen, 2013). Supraglacial melt is able to rapidly reach the bed at elevations below 1000 m via the development of moulins and crevasses (Clason et al, 2014;Bartholomew et al, 2010Bartholomew et al, , 2011, and once it enters the subglacial hydrologic system it can reduce the effective pressure at the ice-bed interface to promote faster sliding.…”

Section: Introductionmentioning

confidence: 99%

Seasonal dynamic thinning at Helheim Glacier

Bevan

Luckman

Khan

et al. 2015

Earth and Planetary Science Letters

Self Cite

View full text Add to dashboard Cite

We investigate three annual mass-balance cycles on Helheim Glacier in south-east Greenland using TanDEM-X interferometric digital elevation models (DEMs), bedrock GPS measurements, and ice velocity from feature-tracking. The DEMs exhibit seasonal surface elevation cycles at elevations up to 800 m.a.s.l. with amplitudes of up to 19 m, from a maximum in July to a minimum in October or November, concentrated on the fast-flowing areas of the glacier indicating that the elevation changes have a mostly dynamic origin. By modelling the detrended bedrock loading/unloading signal we estimate a mean density for the loss of 671 ± 70 kg m −3 and calculate that total water equivalent volume loss from the active part of the glacier (surface flow speeds >1 mday −1 ) ranges from 0.5 km 3 in 2011 to 1.6 km 3 in 2013. A rough ice-flux divergence analysis shows that at lower elevations (<200 m) mass loss by dynamic thinning fully explains seasonal elevation changes. In addition, surface elevations decrease by a greater amount than field observations of surface ablation or surface-energy-balance modelling predict, emphasising the dynamic nature of the mass loss. We conclude, on the basis of ice-front position observations through the time series, that melt-induced acceleration is most likely the main driver of the seasonal dynamic thinning, as opposed to changes triggered by retreat.

show abstract

Section: Introductionmentioning

confidence: 99%

Seasonal dynamic thinning at Helheim Glacier

Bevan

Luckman

Khan

et al. 2015

Earth and Planetary Science Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…Site-position time series recorded by continuous GPS arrays have revealed the vertical displacement variations resulted from trend or seasonal distribution of mass in a region or global changes, e.g. a change of continental water (Bevis et al, 2005;van Dam et al, 2007;Wahr et al, 2013), ice (Sauber et al, 2000;Khan et al, 2010;Nielsen et al, 2013), snow (Heki, 2001;Grapenthin et al, 2006), ocean Wahr et al, 2014), and atmospheric mass (van Dam et al, 1994;Boehm et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Detecting seasonal and long-term vertical displacement in the North China Plain using GRACE and GPS

Wang

Chen

et al. 2017

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. In total, 29 continuous Global Positioning System (GPS) time series data together with data from Gravity Recovery and Climate Experiment (GRACE) are analysed to determine the seasonal displacements of surface loadings in the North China Plain (NCP). Results show significant seasonal variations and a strong correlation between GPS and GRACE results in the vertical displacement component; the average correlation and weighted root-meansquares (WRMS) reduction between GPS and GRACE are 75.6 and 28.9 % respectively, when atmospheric and nontidal ocean effects were removed, but the annual peak-topeak amplitude of GPS (1.2-6.3 mm) is greater than the data (1.0-2.2 mm) derived from GRACE. We also calculate the trend rate as well as the seasonal signal caused by the mass load change from GRACE data; the rate of GRACEderived terrestrial water storage (TWS) loss (after multiplying by the scaling factor) in the NCP was 3.39 cm yr −1 (equivalent to 12.42 km 3 yr −1 ) from 2003 to 2009. For a 10-year time span (2003 to 2012), the rate loss of TWS was 2.57 cm yr −1 (equivalent to 9.41 km 3 yr −1 ), which is consistent with the groundwater storage (GWS) depletion rate (the rate losses of GWS were 2.49 and 2.72 cm yr −1 during 2003-2009 and 2003-2012 respectively) estimated from GRACE-derived results after removing simulated soil moisture (SM) data from the Global Land Data Assimilation System (GLDAS)/Noah model. We also found that GRACEderived GWS changes are in disagreement with the groundwater level changes from observations of shallow aquifers from 2003 to 2009, especially between 2010 and 2013. Although the shallow groundwater can be recharged from the annual climate-driven rainfall, the important facts indicate that GWS depletion is more serious in deep aquifers. The GRACE-derived result shows an overall uplift in the whole region at the 0.37-0.95 mm yr −1 level from 2004 to 2009, but the rate of change direction is inconsistent in different GPS stations at the −0.40-0.51 mm yr −1 level from 2010 to 2013. Then we removed the vertical rates, which are induced by TWS from GPS-derived data, to obtain the corrected vertical velocities caused by tectonic movement and human activities. The results show that there are uplift areas and subsidence areas in NCP. Almost the whole central and eastern region of NCP suffers serious ground subsidence caused by the anthropogenic-induced groundwater exploitation in the deep confined aquifers. In addition, the slight ground uplifts in the western region of NCP are mainly controlled by tectonic movement (e.g. Moho uplifting or mantle upwelling).

show abstract

“…Second, the largest deformation amplitudes were measured during the record‐breaking 2012 melt year. This was previously noted by Nielsen et al [] but was limited to the vertical displacements recorded at four GNET stations.…”

Section: Measurements Of Crustal Motionsmentioning

confidence: 99%

Mass transport waves amplified by intense Greenland melt and detected in solid Earth deformation

Adhikari

Ivins

Larour

2017

Geophysical Research Letters

View full text Add to dashboard Cite

The annual cycle and secular trend of Greenland mass loading are well recorded in measurements of solid Earth deformation. Horizontal crustal displacements can potentially track the spatiotemporal detail of mass changes with great fidelity. Our analysis of Greenland crustal motion data reveals that a significant excitation of horizontal amplitudes occurs during the intense melt years. We discover that solitary seasonal waves of substantial mass transport (1.67 ± 0.54 Gt/month) traveled at an average speed of 7.1 km/month through Rink Glacier in 2012. We deduce that intense surface melting enhanced either basal lubrication or softening of shear margins, or both, causing the glacier to thin dynamically in summer. The newly routed upstream subglacial water was likely to be both retarded and inefficient, thus providing a causal mechanism for the prolonged ice transport to continue well into the winter months. As the climate continues to produce increasingly warmer spring and summer, amplified seasonal waves of mass transport may become ever more present with important ramifications for the future sea level rise.

show abstract

Vertical and horizontal surface displacements near Jakobshavn Isbræ driven by melt‐induced and dynamic ice loss

Cited by 35 publications

References 35 publications

Seasonal dynamic thinning at Helheim Glacier

Seasonal dynamic thinning at Helheim Glacier

Detecting seasonal and long-term vertical displacement in the North China Plain using GRACE and GPS

Mass transport waves amplified by intense Greenland melt and detected in solid Earth deformation

Contact Info

Product

Resources

About