Spatio-temporal evolution of the Greenland ice sheet and associated deformation of the Earth: a multi-technic geodetic approach

2021 ◽  
Author(s):  
Ana Sanchez ◽  
Laurent Métivier ◽  
Luce Fleitout ◽  
Kristel Chanard ◽  
Greff Marianne
Keyword(s):  
Temporal Evolution ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Planetary Science ◽  
Ice Age ◽  
Potential Contribution ◽  
Ice Melting ◽  
Viscoelastic Deformation ◽  
Important Indicator ◽  
Spatio Temporal

<p>The evolution of the Greenland Ice Sheet (GIS) is an important indicator of climate change and driver of sea level rise. However, providing accurate GIS ice mass balance remains a challenge today. Here, we propose to combine a unique set of geodetic measurements to improve our knowledge of the GIS spatial and temporal evolution. We attempt at reconciling satellite observations of ice volume with regional GNSS velocities estimates and time variable space gravity measurements over the 2003-2009 and 2011-2015 periods. The GIS mass variations are inferred from satellite altimetry for large ice sheets (IceSat and CryoSat-2; Sorensen et al.,2018, Simonsen et al.,2017) and digital elevation models (DEMs) generated from multiple satellite archives for peripheral glaciers (Hugonnet et al.,2020), associated with IMAU-FDM firn model (Ligtenberg et al., 2011). The spatial and temporal variations of the gravity field are given by the GRACE mission for which we use a solution where smaller wavelength signals are preserved (Prevost et al., 2019).</p><p>To resolve short wavelengths load variations affecting the displacement of nearby GNSS stations, we use Green’s functions for vertical crustal displacements assuming purely elastic Earth properties (Martens et al., 2019). We first assume that the deformation is entirely due to recent ice melting and show that vertical elastic displacements predicted by our refined ice loading model, while in good agreement with observations in some regions, cannot explain observations overall. In particular, observations and model disagree in the Southeastern and the Northern parts of Greenland.</p><p>We then explore potential viscoelastic deformation associated with short-term rheology of the asthenosphere induced by recent ice melting that could explain the observed GNSS displacements. We define a history of ice loading from 1900 to 2009 using both in situ and satellite altimetric measurements, compute today’s associated viscoelastic deformation for various mantle rheologies and discuss the potential contribution of ice melting since the little ice age to current observations. Remaining differences between observations and viscoelastic models may reflect a viscoelastic deformation induced by glacial isostatic adjustment. We discuss implications in terms of regional rheological constraints, and impact on estimates of present-day GIS ice mass budget.</p><p>Hugonnet, R. (2020). A globally complete, spatially, and temporally resolved estimate of glacier mass change: 2000 to 2019. In EGU 2020. </p><p>Ligtenberg, S. R. M., et al (2011). An improved semi-empirical model for the densification of Antarctic firn. The Cryosphere, 5, 809-819.</p><p>Martens, H. R.,et al (2019). LoadDef: A Python‐based toolkit to model elastic deformation caused by surface mass loading on spherically symmetric bodies. Earth and Space Science, 6(2), 311-323.</p><p>Prevost, P., et al (2019). Data-adaptive spatio-temporal filtering of GRACE data. Geophysical Journal International, 219(3), 2034-2055.</p><p>Simonsen, S. B., & Sørensen, L. S. (2017). Implications of changing scattering properties on Greenland ice sheet volume change from Cryosat-2 altimetry. Remote Sensing of Environment, 190, 207-216.</p><p>Sørensen, L. S., et al (2018). 25 years of elevation changes of the Greenland Ice Sheet from ERS, Envisat, and CryoSat-2 radar altimetry. Earth and Planetary Science Letters, 495, 234-241.</p>

Greenland fjord productivity under climate change - multiproxy late-Holocene records from two contrasting fjord systems

2020 ◽  
Author(s):  
Anna Bang Kvorning ◽  
Tania Beate Thomsen ◽  
Mimmi Oksman ◽  
Marit-Solveig Seidenkrantz ◽  
Christof Pearce ◽  
...  
Keyword(s):  
Climate Change ◽  
Primary Productivity ◽  
Negative Impact ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Dinoflagellate Cyst ◽  
Coastal Marine ◽  
The Future ◽  
The Impact

<p>The Greenland Ice Sheet has been losing mass at an increasing rate over the past decades due to atmospheric and oceanic warming. As a result, freshwater discharge from the Greenland Ice sheet has doubled in the last two decades and is expected to strongly increase in the future, with a large impact on the functioning of coastal marine ecosystems. While glacier runoff delivers nutrients and labile carbon into the fjords, an increase in sediment inputs is expected to have a negative impact in primary productivity, due to increased turbidity and subsequent reduction in available light for photosynthesis. Bridging modern satellite, historical and paleo-records is a key approach, as our capacity to project future scenarios requires an understanding of long-term dynamics, and insight into past warm(er) climate periods that may serve as analogues for the future. We will present results from a master’s project developed within the framework of project GreenShift: Greenland fjord productivity under climate change. Two high-resolution sediment core records from two contrasting fjord systems in NE and SW Greenland were analysed to assess the impact of Greenland Ice Sheet melt on sediment fluxes and primary productivity, focusing on the time period from the Little Ice Age until present. The overall goal of this work is to gain a better understanding of the possible linkages between GIS melt and productivity in Greenland fjord systems, with a view to improve future projections. We followed a multiproxy approach including grain-size distribution, organic carbon and biogenic silica fluxes; and dinoflagellate cyst analyses. Our preliminary results show an overall trend towards sea-surface freshening in recent decades for both fjords influenced by land-terminating (NE) and marine-terminating (SW) glaciers, alongside with important differences both in terms of sedimentary organic composition and dinoflagellate cyst assemblages.  </p>

scholarly journals Ice-age ice-sheet rheology: constraints from the Last Glacial Maximum form of the Laurentide ice sheet

2000 ◽  
Vol 30 ◽  
pp. 163-176 ◽  
Author(s):  
W. Richard Peltier ◽  
David L. Goldsby ◽  
David L. Kohlstedt ◽  
Lev Tarasov
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacial Maximum ◽  
Ice Age ◽  
Laurentide Ice Sheet ◽  
Last Glacial ◽  
Flow Law ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractState-of-the-art thermomechanical models of the modern Greenland ice sheet and the ancient Laurentide ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurentide ice sheet, predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation then the aspect ratios of both the modern Greenland ice sheet and the Laurentide ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

Colonisation of Greenland by plants and animals after the last ice age: a review

Polar Record ◽  
1999 ◽  
Vol 35 (195) ◽  
pp. 323-336 ◽  
Author(s):  
Ole Bennike
Keyword(s):  
Endemic Species ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Long Distance ◽  
Cold Adapted ◽  
Northwest Europe ◽  
Last Ice Age ◽  
Sea Currents ◽  
Wind Sea

AbstractIn the light of data from the Greenland ice sheet concerning the ice-age climate, and palaeoecological studies of interglacial and Early Holocene deposits, the concept that a large proportion of Greenland's plants and animals may have survived during the ice ages is evaluated. While ice-free areas (refugias) were present, it is concluded that only hardy, cold-adapted species could have survived, which also explains why so few clearly endemic species are present in Greenland. Most members of the present biota are considered to be postglacial immigrants. Some species came to Greenland by walking or flying, but most arrived by passive, long-distance, chance dispersal, carried by wind, sea currents, and, in particular, birds. Transport by birds may explain why so many species arrived from Europe, because vast numbers of geese in particular migrate from northwest Europe to Greenland.

scholarly journals Asynchronous Antarctic and Greenland ice-volume contributions to the last interglacial sea-level highstand

2020 ◽  
Author(s):  
Eelco Rohling ◽  
Fiona Hibbert
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Global Climate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Climate Forcing ◽  
Potential Contribution ◽  
Last Interglacial ◽  
Ice Shelf

<p>Sea-level rise is among the greatest risks that arise from anthropogenic global climate change. It is receiving a lot of attention, among others in the IPCC reports, but major questions remain as to the potential contribution from the great continental ice sheets. In recent years, some modelling work has suggested that the ice-component of sea-level rise may be much faster than previously thought, but the rapidity of rise seen in these results depends on inclusion of scientifically debated mechanisms of ice-shelf decay and associated ice-sheet instability. The processes have not been active during historical times, so data are needed from previous warm periods to evaluate whether the suggested rates of sea-level rise are supported by observations or not. Also, we then need to assess which of the ice sheets was most sensitive, and why. The last interglacial (LIG; ~130,000 to ~118,000 years ago, ka) was the last time global sea level rose well above its present level, reaching a highstand of +6 to +9 m or more. Because Greenland Ice Sheet (GrIS) contributions were smaller than that, this implies substantial Antarctic Ice Sheet (AIS) contributions. However, this still leaves the timings, magnitudes, and drivers of GrIS and AIS reductions open to debate. I will discuss recently published sea-level reconstructions for the LIG highstand, which reveal that AIS and GrIS contributions were distinctly asynchronous, and that rates of rise to values above 0 m (present-day sea level) reached up to 3.5 m per century. Such high pre-anthropogenic rates of sea-level rise lend credibility to high rates inferred by ice modelling under certain ice-shelf instability parameterisations, for both the past and future. Climate forcing was distinctly asynchronous between the southern and northern hemispheres as well during the LIG, explaining the asynchronous sea-level contributions from AIS and GrIS. Today, climate forcing is synchronous between the two hemispheres, and also faster and greater than during the LIG. Therefore, LIG rates of sea-level rise should likely be considered minimum estimates for the future.</p>

scholarly journals Glacial history of Inglefield Land, north Greenland from combined in-situ <sup>10</sup>Be and <sup>14</sup>C exposure dating

2020 ◽  
Author(s):  
Anne Sofie Søndergaard ◽  
Nicolaj Krog Larsen ◽  
Olivia Steinemann ◽  
Jesper Olsen ◽  
Svend Funder ◽  
...  
Keyword(s):  
Climate Changes ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Glacial History ◽  
Holocene Climate ◽  
Exposure Dating ◽  
History Of ◽  
North Greenland

Abstract. Exposing the sensitivity of the Greenland Ice Sheet (GrIS) to Holocene climate changes is a key prerequisite for understanding the future response of the ice sheet to global warming. In this study, we present new information on the Holocene glacial history of the GrIS in Inglefield Land, north Greenland. We use 10Be and in-situ 14C exposure dating to constrain the timing of deglaciation in the area and radiocarbon dating of reworked molluscs and wood fragments to constrain when the ice sheet retreated behind its present-day extent. The 10Be ages are scattered ranging from c. 92.7 to 6.8 ka whereas the in-situ 14C ages range from c. 14.2 to 6.7 ka. Almost half of the apparent 10Be ages predate the Last Glacial Maximum and up to 89 % are to some degree affected by nuclide inheritance. Based on the few reliable 10Be ages, the in-situ 14C ages and existing radiocarbon ages from Inglefield Land, we find that the deglaciation along the coast commenced c. 8.6–8.3 cal. ka BP in the western part and c. 7.9 ka in the central part, following the opening of Nares Strait and arrival of warm waters. The ice margin reached its present-day position c. 8.2 ka at the Humboldt Glacier and c. 6.7 ka in the central part of Inglefield Land. Radiocarbon ages of reworked molluscs and wood fragments show that the ice margin was behind its present-day extent from c. 5.8 to 0.5 cal. ka BP. After 0.5 cal. ka BP, the ice advanced towards its Little Ice Age position. Our results emphasize that the slowly eroding and possibly cold-based ice in north Greenland makes it difficult to constrain the deglaciation history based on 10Be ages alone unless it is paired with in-situ 14C ages. Further, combining our findings with those of recently published studies reveals distinct differences between deglaciation patterns of northwest and north Greenland. Deglaciation of the land areas in northwest Greenland occurred earlier than in north Greenland and periods of restricted ice extent were longer, spanning middle and late Holocene. Overall, this highlights past ice sheet sensitivity towards Holocene climate changes in an area where little information was available just a few years ago.

scholarly journals Organic matter content and quality in supraglacial debris across the ablation zone of the Greenland ice sheet

2010 ◽  
Vol 51 (56) ◽  
pp. 1-8 ◽  
Author(s):  
Marek Stibal ◽  
Emily C. Lawson ◽  
Grzegorz P. Lis ◽  
Ka Man Mak ◽  
Jemma L. Wadham ◽  
...  
Keyword(s):  
Organic Matter Content ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Dry Weight ◽  
Matter Content ◽  
Microbial Abundance ◽  
Physical Processes ◽  
Important Indicator ◽  
Microbial Productivity

AbstractQuantifying the biogeochemical cycling of carbon in glacial ecosystems is of great significance for regional, and potentially global, carbon flow estimations. The concentration and quality of organic carbon (OC) is an important indicator of biogeochemical and physical processes that prevail in an ice-sheet ecosystem. Here we determine the content and quality of OC in debris from the surface of the Greenland ice sheet (GrIS) using microscopic, chromatographic, spectrophotometric and high-temperature combustion techniques. The total OC content in the debris increased with distance from the edge of the ice sheet, from virtually zero to >6% dry weight at 50 km inland, and there was a peak in the carbohydrate proportion and the microbial abundance at ∼6km inland. The highest (galactose + mannose)/(arabinose + xylose) ratios, indicating maximum autochthonous microbial production, were found at >10km inland. We propose that three key processes influence the carbon cycling on the GrIS: aeolian input of microbial inoculum and nutrients, in situ biological C transformation and the wash-away of supraglacial debris by meltwaters. We show that all these processes have significant spatial variability. While the total OC content of the debris on the ice sheet is probably controlled by the physical processes of wind transport and wash-away by meltwater, the microbial abundance and the quantity of the labile cell-contained OC within the debris is likely to be driven by the balance between the wash-away and the microbial productivity.

scholarly journals Ryder Glacier in northwest Greenland is shielded from warm Atlantic water by a bathymetric sill

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Martin Jakobsson ◽  
Larry A. Mayer ◽  
Johan Nilsson ◽  
Christian Stranne ◽  
Brian Calder ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atlantic Water ◽  
The Arctic ◽  
Subsurface Water ◽  
Ice Melting ◽  
Warming Climate ◽  
Atlantic Origin ◽  
Oceanographic Data ◽  
Insight Into

Abstract The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of the Greenland Ice Sheet has increased six-fold over the last four decades, with discharge and melt from outlet glaciers comprising key components of this loss. Here we acquired oceanographic data and multibeam bathymetry in the previously uncharted Sherard Osborn Fjord in northwest Greenland where Ryder Glacier drains into the Arctic Ocean. Our data show that warmer subsurface water of Atlantic origin enters the fjord, but Ryder Glacier’s floating tongue at its present location is partly protected from the inflow by a bathymetric sill located in the innermost fjord. This reduces under-ice melting of the glacier, providing insight into Ryder Glacier’s dynamics and its vulnerability to inflow of Atlantic warmer water.

scholarly journals Surface outburst of a subglacial flood from the Greenland Ice Sheet

2021 ◽  
Author(s):  
Jade Bowling ◽  
Amber Leeson ◽  
Malcolm McMillan ◽  
Stephen Livingstone ◽  
Andrew Sole ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Theoretical Models ◽  
Arctic Climate ◽  
Ice Melting ◽  
Subglacial Lake ◽  
The Past ◽  
Ice Surface ◽  
Earth’S Climate

Abstract As Earth’s climate warms, surface melting of the Greenland Ice Sheet is projected to intensify, contributing to rising sea levels1–4. Observations5–7 and theory8–10 indicate that meltwater generated at the surface of an ice sheet can drain to its bed via crevasses and moulins, where it flows relatively unhindered to the coast. This understanding of the movement of water within, and beneath, ice sheets, underpins theoretical models which are used to make projections of ice sheet change11. In this study, we show the first evidence of a disruptive drainage pathway in Greenland, whereby a subglacial flood – triggered by a draining subglacial lake – breaks through the ice sheet surface. This unprecedented outburst of water causes fracturing of the ice sheet, and the formation of 25-metre-high ice blocks. These observations reveal a complex, bidirectional coupling between the surface and basal hydrological systems of an ice sheet, which was previously unknown in Greenland. Analysis of over 30 years of satellite imagery confirms that the subglacial lake has drained at least once previously. However, on that occasion the floodwater failed to breach the ice surface. The two contrasting drainage regimes, coupled with the increased rates of ice melting and thinning that have occurred over the past three decades years, suggest that Arctic climate warming may have facilitated a new, disruptive mode of hydrological drainage on the ice sheet. As such, our observations reveal an emerging and poorly understood phenomenon, which is not currently captured in physical ice sheet models.

Magnetotelluric Constraints on Upper Mantle Viscosity Structure and Basal Melt Beneath the Greenland Ice Sheet

2020 ◽  
Author(s):  
Clinton Conrad ◽  
Kate Selway ◽  
Maaike Weerdesteijn ◽  
Silje Smith-Johnsen ◽  
Kerim Nisancioglu ◽  
...  
Keyword(s):  
Mass Loss ◽  
Upper Mantle ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Quality Data ◽  
Good Resolution ◽  
Mantle Viscosity ◽  
Ice Stream ◽  
Iceland Plume

&lt;p&gt;Mass loss from the Greenland Ice Sheet has accelerated during the past decade due to climate warming. This deglaciation is now considered a major contributor to global sea level rise, and a serious threat to future coastlines. It is therefore vital to measure patterns and volumes of ice sheet mass loss. However, measurements of the ice sheet&amp;#8217;s mass and elevation, both of which decrease as the ice melts, are also sensitive to ground deformation associated with glacial isostatic adjustment (GIA), which is the solid Earth&amp;#8217;s response to ice loss since the last ice age. For Greenland, GIA is poorly constrained in part because Greenland&amp;#8217;s complex geologic history, with a passage over the Iceland Plume, probably created large lateral viscosity variations beneath Greenland that complicate the GIA response.&lt;/p&gt;&lt;p&gt;The Norwegian MAGPIE project (Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution) seeks to develop new constraints on mantle viscosity beneath Greenland by collecting magnetotelluric (MT) data on the ice sheet. MT images the Earth&amp;#8217;s electrical conductivity, which is sensitive to three of the major controls on mantle viscosity: temperature, partial melt content and water content of solid-state mantle minerals. We therefore plan to use MT data, together with existing seismic data, to map viscosity variations beneath Greenland. During the summer of 2019 we deployed 13 MT stations in a 200 km grid centered on EastGRIP camp on the North-East Greenland Ice Stream. Good quality data were recorded at periods up to 10,000 s, providing good resolution of upper mantle conductivity structure. We also collected a broadband MT traverse across the NE Greenland Ice Stream, which allows us to directly compare MT and radar data to investigate the role of basal melt on ice flow dynamics. During the 2020 summer season we will be collecting additional data over the south-western and central parts of the ice sheet. Here we show preliminary constraints on the conductivity of the asthenosphere, lithosphere, and crust beneath Greenland, which will be used to investigate the upper mantle viscosity structure, including the present-day signature of the Iceland Plume.&lt;/p&gt;

scholarly journals Statistical-Dynamical Model of Accumulation on the Greenland Ice Sheet

1984 ◽  
Vol 5 ◽  
pp. 69-74 ◽  
Author(s):  
Richard A. Keen
Keyword(s):  
Moisture Content ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Relative Vorticity ◽  
Ice Age ◽  
Cyclonic Activity ◽  
Atmospheric Moisture ◽  
Distribution Maps ◽  
Southern Half ◽  
Atmospheric Moisture Content

A relatively simple, three-parameter model is used to simulate the annual precipitation (accumulation) distribution for the Greenland ice sheet and surrounding regions. The three parameters are (1) the flux of relative vorticity at the 500 mbar level (a measure of cyclonic activity), (2) atmospheric moisture content, and (3) surface terrain. The climatological (1946–79) precipitation distribution predicted by the model displays major features of the observed distribution derived from pit studies. However, the model suggests that, due to changes in storm tracks during this period of 33 a, accumulation distribution maps based on pit studies for varying periods of record may not be representative of a true mean for a uniform period of record. The model is then applied to reconstructed ice-age conditions. Compared to present conditions, accumulation reductions of 60¾ or more are indicated for much of the southern half of Greenland; only slight reductions are noted for northern Greenland.

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