Highly temporally resolved response to seasonal surface melt of the Zachariae and 79N outlet glaciers in northeast Greenland

Rathmann, Nicholas; Hvidberg, Christine S.; Solgaard, Anne; Grinsted, Aslak; Gudmundsson, G. Hilmar; Langen, Peter L.; Nielsen, Kristian Pagh; Kusk, Anders

doi:10.1002/2017gl074368

Cited by 34 publications

(46 citation statements)

References 69 publications

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“…Only when results are fully reproducible -meaning all necessary data and code are available (cf. Mankoff and Tulaczyk, 2017;Rezvanbehbahani et al, 2017) -can new works confidently attribute discrepancies relative to old works. Therefore, in addition to providing new discharge estimates, we attempt to examine discrepancies among our estimates and other recent estimates.…”

Section: Discussionmentioning

confidence: 99%

Greenland Ice Sheet solid ice discharge from 1986 through 2017

Mankoff

Colgan

Solgaard

et al. 2019

Earth Syst. Sci. Data

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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.

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Section: Discussionmentioning

confidence: 99%

Greenland Ice Sheet solid ice discharge from 1986 through 2017

Mankoff

Colgan

Solgaard

et al. 2019

Earth Syst. Sci. Data

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“…Interannual velocity fluctuations and resulting mass loss due to ice discharge via marine-terminating glaciers in Greenland are relatively well characterized (Andersen et al, 2015;Enderlin et al, 2014;Howat et al, 2007;Mouginot et al, 2015;Rignot et al, 2004;Schlegel et al, 2014). Previous studies have also reported seasonal velocity variability for different glacier systems in Greenland and provided evidence of potential driving mechanisms (Bevan et al, 2015;Howat et al, 2008;Kjeldsen et al, 2017;Moon et al, 2012;Moon et al, 2014;Rathmann et al, 2017). Previous studies have also reported seasonal velocity variability for different glacier systems in Greenland and provided evidence of potential driving mechanisms (Bevan et al, 2015;Howat et al, 2008;Kjeldsen et al, 2017;Moon et al, 2012;Moon et al, 2014;Rathmann et al, 2017).…”

Section: Introductionmentioning

confidence: 97%

Resolving Seasonal Ice Velocity of 45 Greenlandic Glaciers With Very High Temporal Details

Vijay

Khan

Kusk

et al. 2019

Geophysical Research Letters

146

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Seasonal glacier ice velocities are important for understanding controlling mechanisms of ice flow. For many Greenlandic glaciers, however, these measurements are limited by low temporal resolution. We present seasonal ice velocity changes, melt season onset and extent, and ice front positions for 45 Greenlandic glaciers using 2015–2017 Sentinel‐1 synthetic aperture radar data. Seasonal velocity fluctuations of roughly half of the glaciers appear to be primarily controlled by surface melt‐induced changes in the subglacial hydrology. This includes (1) glaciers that speed up with the onset of surface melt and (2) glaciers with comparable late winter and early melt season velocities that show significant slowdown during most of the melt season and speedup during winter. In contrast, less than a quarter of the study glaciers show strong correspondence between seasonal ice speed and terminus changes. Our results pinpoint seasonal variations across Greenland, highlighting the variable influence of meltwater on year‐round ice velocities.

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“…The break-up of ice shelves that stabilise the outlet glaciers can lead to accelerations in ice velocity and therefore higher rates of sea level rise [29], but different glaciers respond in different ways to changes at the front [86] and careful modelling studies in combination with good observational data are required to understand the important processes [87]. For example, Rathmann et al [21] showed different seasonal accelerations at neighbouring glaciers Zachariae Isstrøm and 79 glacier in response to very similar runoff rates. Part of the differences were explained by different hydrological regimes but there is also a possibility that response to a climate forcing may be delayed by other glaciological processes such as differing bed topographies, geothermal heat flux or past strain histories.…”

Section: Calving Front Location and Ice Sheet Mass Budgetmentioning

confidence: 99%

“…By consolidating, standardising and integrating satellite remote sensing data, high quality datasets are now accessible to scientists, policymakers and other stakeholders. This data has been used to identify significant trends and changes in ice dynamics in Greenland including identifying significant changes in ice velocity at large outlet glaciers [16], assessing the causes of surface elevation change across the ice sheet [17][18][19][20] as well as assessing the importance of different processes controlling seasonal velocity changes on the ice sheet [21]. The availability of this data is invaluable in communicating the effects of climate change on the cryosphere and the likely impacts on sea level rise and human societies.…”

Section: Introductionmentioning

confidence: 99%

An Integrated View of Greenland Ice Sheet Mass Changes Based on Models and Satellite Observations

Mottram

Simonsen²,

Svendsen³

et al. 2019

Remote Sensing

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The Greenland ice sheet is a major contributor to sea level rise, adding on average 0.47 ± 0.23 mm year − 1 to global mean sea level between 1991 and 2015. The cryosphere as a whole has contributed around 45% of observed global sea level rise since 1993. Understanding the present-day state of the Greenland ice sheet is therefore vital for understanding the processes controlling the modern-day rates of sea level change and for making projections of sea level rise into the future. Here, we provide an overview of the current state of the mass budget of Greenland based on a diverse range of remote sensing observations to produce the essential climate variables (ECVs) of ice velocity, surface elevation change, grounding line location, calving front location, and gravimetric mass balance as well as numerical modelling that together build a consistent picture of a shrinking ice sheet. We also combine these observations with output from a regional climate model and from an ice sheet model to gain insight into existing biases in ice sheet dynamics and surface mass balance processes. Observations show surface lowering across virtually all regions of the ice sheet and at some locations up to −2.65 m year − 1 between 1995 and 2017 based on radar altimetry analysis. In addition, calving fronts at 28 study sites, representing a sample of typical glaciers, have retreated all around Greenland since the 1990s and in only two out of 28 study locations have they remained stable. During the same period, two of five floating ice shelves have collapsed while the locations of grounding lines at the remaining three floating ice shelves have remained stable over the observation period. In a detailed case study with a fracture model at Petermann glacier, we demonstrate the potential sensitivity of these floating ice shelves to future warming. GRACE gravimetrically-derived mass balance (GMB) data shows that overall Greenland has lost 255 ± 15 Gt year − 1 of ice over the period 2003 to 2016, consistent with that shown by IMBIE and a marked increase compared to a rate of loss of 83 ± 63 Gt year − 1 in the 1993–2003 period. Regional climate model and ice sheet model simulations show that surface mass processes dominate the Greenland ice sheet mass budget over most of the interior. However, in areas of high ice velocity there is a significant contribution to mass loss by ice dynamical processes. Marked differences between models and observations indicate that not all processes are captured accurately within models, indicating areas for future research.

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Highly temporally resolved response to seasonal surface melt of the Zachariae and 79N outlet glaciers in northeast Greenland

Cited by 34 publications

References 69 publications

Greenland Ice Sheet solid ice discharge from 1986 through 2017

Greenland Ice Sheet solid ice discharge from 1986 through 2017

Resolving Seasonal Ice Velocity of 45 Greenlandic Glaciers With Very High Temporal Details

An Integrated View of Greenland Ice Sheet Mass Changes Based on Models and Satellite Observations

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