scholarly journals The impact of model resolution on the simulated Holocene retreat of the southwestern Greenland ice sheet using the Ice Sheet System Model (ISSM)

2019 ◽  
Vol 13 (3) ◽  
pp. 879-893 ◽  
Author(s):  
Joshua K. Cuzzone ◽  
Nicole-Jeanne Schlegel ◽  
Mathieu Morlighem ◽  
Eric Larour ◽  
Jason P. Briner ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Horizontal Resolution ◽  
System Model ◽  
Model Parameters ◽  
Uniform Mesh ◽  
Model Resolution ◽  
The Holocene ◽  
Bed Topography ◽  
The Impact

Abstract. Geologic archives constraining the variability of the Greenland ice sheet (GrIS) during the Holocene provide targets for ice sheet models to test sensitivities to variations in past climate and model formulation. Even as data–model comparisons are becoming more common, many models simulating the behavior of the GrIS during the past rely on meshes with coarse horizontal resolutions (≥10 km). In this study, we explore the impact of model resolution on the simulated nature of retreat across southwestern Greenland during the Holocene. Four simulations are performed using the Ice Sheet System Model (ISSM): three that use a uniform mesh and horizontal mesh resolutions of 20, 10, and 5 km, and one that uses a nonuniform mesh with a resolution ranging from 2 to 15 km. We find that the simulated retreat can vary significantly between models with different horizontal resolutions based on how well the bed topography is resolved. In areas of low topographic relief, the horizontal resolution plays a negligible role in simulated differences in retreat, with each model instead responding similarly to retreat driven by surface mass balance (SMB). Conversely, in areas where the bed topography is complex and high in relief, such as fjords, the lower-resolution models (10 and 20 km) simulate unrealistic retreat that occurs as ice surface lowering intersects bumps in the bed topography that would otherwise be resolved as troughs using the higher-resolution grids. Our results highlight the important role that high-resolution grids play in simulating retreat in areas of complex bed topography, but also suggest that models using nonuniform grids can save computational resources through coarsening the mesh in areas of noncomplex bed topography where the SMB predominantly drives retreat. Additionally, these results emphasize that care must be taken with ice sheet models when tuning model parameters to match reconstructed margins, particularly for lower-resolution models in regions where complex bed topography is poorly resolved.

scholarly journals The impact of model resolution on the simulated Holocene retreat of the Southwestern Greenland Ice Sheet using the Ice Sheet System Model (ISSM)

2018 ◽  
Author(s):  
Joshua K. Cuzzone ◽  
Nicole-Jeanne Schlegel ◽  
Mathieu Morlighem ◽  
Eric Larour ◽  
Jason P. Briner ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
System Model ◽  
Model Parameters ◽  
Uniform Mesh ◽  
Model Resolution ◽  
The Holocene ◽  
Bed Topography ◽  
Uniform Grids ◽  
The Impact

Abstract. Geologic archives constraining the variability of the Greenland Ice Sheet (GrIS) during the Holocene provide targets for ice sheet models to test sensitivities to variations in past climate and model formulation. Even as data-model comparisons are becoming more common, many models simulating the behaviour of the GrIS during the past rely on meshes with coarse horizontal resolution (≥ 10 km). In this study, we explore the impact of model resolution on the simulated nature of retreat across Southwestern Greenland during the Holocene. Four simulations are performed using the Ice Sheet System Model (ISSM); three which use a uniform mesh and horizontal mesh resolutions of 20 km, 10 km, and 5 km and one non-uniform mesh with resolution ranging from 2 km to 15 km. We find that the simulated retreat can vary significantly between models with different horizontal resolutions based on how well the bed topography is resolved. In areas of low topographic relief, model resolution plays a negligible role in simulated differences in retreat, with models instead responding similarly to surface mass balance (SMB) driven retreat. Conversely, in areas where the bed topography is complex and high in relief, such as fjords, lower resolution models (10 km and 20 km) simulate unrealistic retreat driven as ice-surface lowering intersects bumps in the bed topography which would otherwise be resolved as troughs in the higher resolution models. Our results highlight the important role that high resolution grids play in simulating retreat in areas of complex bed topography, but also suggest that models using non-uniform grids can save computational resources through coarsening the mesh in areas of non-complex bed topography where the SMB drives retreat. Additionally, these results emphasize that care must be taken with ice sheet models when tuning model parameters to match reconstructed margins, particularly for lower resolution models in regions where complex bed topography is poorly resolved.

Modelled Holocene thinning in Greenland improved by new developed transient past climatologies.

2021 ◽  
Author(s):  
Ilaria Tabone ◽  
Alexander Robinson ◽  
Jorge Alvarez-Solas ◽  
Javier Blasco ◽  
Daniel Moreno ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Model Parameters ◽  
Last Deglaciation ◽  
The Holocene ◽  
Model Mismatch ◽  
Elevation Changes ◽  
The Impact

<p>Reconstructions of Greenland Summit elevation changes indicate at least 150 m of surface thinning since the onset of the Holocene. Even higher thinning values are found at locations closer to the ice-sheet margin, where the influence of higher ablation rates and ocean-induced retreat is greater. Interestingly, the performance of 3D ice-sheet models in representing such elevation changes is generally poor, even though they can reasonably reproduce the state of the ice sheet at different times, such as the last glacial maximum (LGM) or the present day. The reasons behind this data-model mismatch are still unclear. Here we use a recently developed 3D ice-sheet-shelf model to test the impact of different model parameters and of boundary conditions on simulating the Greenland ice sheet evolution through the last deglaciation to today. Specifically, we investigate the role of past climatologies in reproducing the elevation changes at ice core sites when used to force the ice-sheet model. By applying recently developed transient deglacial climatologies we can investigate the ice-sheet deglaciation with exceptional detail. Results support the need of additional transient climatologies to be released to ensure a robust description of the Greenland retreat history throughout the Holocene. </p>

scholarly journals The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

2013 ◽  
Vol 9 (4) ◽  
pp. 1629-1643 ◽  
Author(s):  
M. Blaschek ◽  
H. Renssen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Surface Cooling ◽  
Holocene Climate ◽  
Nordic Seas ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum ◽  
The Impact

Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

scholarly journals The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere-sea ice-ocean model

2012 ◽  
Vol 8 (5) ◽  
pp. 5263-5291 ◽  
Author(s):  
M. Blaschek ◽  
H. Renssen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Surface Cooling ◽  
Holocene Climate ◽  
Nordic Seas ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum ◽  
The Impact

Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene Thermal Maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveal a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from a previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in a ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that the modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

Late Holocene thermohaline perturbation of the N-Atlantic Subpolar Gyre linked to exceptional Greenland Ice Sheet melting between 4.4 and 4.0 ka BP

2020 ◽  
Author(s):  
Antoon Kuijpers ◽  
Marit-Solveig Seidenkrantz ◽  
Ralph Schneider ◽  
Camilla S. Andresen ◽  
Signe Hygom Jacobsen ◽  
...  
Keyword(s):  
Late Holocene ◽  
Deep Convection ◽  
Water Discharge ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Subpolar Gyre ◽  
The Holocene ◽  
Master Thesis ◽  
The Impact

<p>Knowledge of the impact of past climate warming on Greenland Ice Sheet stability is an important issue for assessing  thresholds that are critical for a potential ice sheet collapse. For the late Holocene, evidence has recently been found of a so-called 4.2 ka BP event(1) including a prominent warming spike in several ice core records from Greenland and Canada (Agassiz).  Also lake records from both Northwest(2) and South Greenland(3) support pronounced summer warming during that time. After c. 4.0 ka BP NW Greenland July air temperature dropped by about 3<sup>o</sup> C. Coeval with this exceptional atmospheric warming anomaly over northern Canada and parts of Greenland, abrupt cooling and freshening affected  the N-Atlantic subpolar gyre where Labrador Sea deep convection ceased(4). Northern N-Atlantic climate generally deteriorated. With our contribution we present Holocene sub-bottom profiling  and sedimentary shelf and  fjord records from Southwest Greenland and Disko Bay that indicate exceptional Greenland Ice Sheet melting 4.4-4.0 ka BP at a rate and magnitude not recorded since early Holocene deglaciation. Extremely strong melt water discharge resulted in erosion of fjord sediments(5) and local deposition of up to several meters thick meltwater sediment on the shelf(6-8).  Timing of this melting event corresponds to a significant anomaly in hydrographic parameters of the Labrador Current off Newfoundland(9,10), which is concluded to have resulted in thermohaline perturbation of the N-Atlantic Subpolar gyre.   </p><ul><li>(1) Weiss, H. 2019. Clim Past doi:10.5194/cp-2018-162-RC2</li> <li>(2) McFarlin, J.M. et al. 2018. PNAS doi:10.1073/pnas.1720420115</li> <li>(3) Andresen, C.S. et al. 2004. J Quat Sci 19(8) doi:10.1002/jqs.886</li> <li>(4) Klus, A. et al. 2018. Clim Past doi:10.5194/cp-14-1165-2018</li> <li>(5) Ren, J. et al. 2009. Mar Micropal doi:10.1016/j.marmicro.2008.12.003</li> <li>(6) Hygom Jacobsen, S. 2019. Master Thesis Aarhus Univ, Dept. of Geoscience, pp105</li> <li>(7) Schneider, R. 2015. Cruise Rep epic.awi.de/id/eprint/37062/131/msm-44-46-expeditionsheft.pdf</li> <li>(8) Kuijpers, A. et al. 2001. Geol. Greenland Surv Bull 189, 41-47</li> <li>(9) Solignac, S. et al. 2011. The Holocene, doi: 10.1177/0959683610385720</li> <li>(10) Orme, L. et al 2019. The Holocene (submitted)</li> </ul>

scholarly journals A new bedrock and surface elevation dataset for modelling the Greenland ice sheet

2003 ◽  
Vol 37 ◽  
pp. 351-356 ◽  
Author(s):  
Jonathan L. Bamber ◽  
Duncan J. Baldwin ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Detailed Comparison ◽  
Radar Data ◽  
The Arctic ◽  
Small Scale ◽  
Surface Model ◽  
Rock Outcrops ◽  
Bed Topography ◽  
Elevation Model

AbstractA new digital elevation model of the surface of the Greenland ice sheet and surrounding rock outcrops has been produced from a comprehensive suite of satellite and airborne remote-sensing and cartographic datasets. The surface model has been regridded to a resolution of 5 km, and combined with a new ice-thickness grid derived from ice-penetrating radar data collected in the 1970s and 1990s. A further dataset, the International Bathymetric Chart of the Arctic Ocean, was used to extend the bed elevations to include the continental shelf. The new bed topography was compared with a previous version used for ice-sheet modelling. Near the margins of the ice sheet and, in particular, in the vicinity of small-scale features associated with outlet glaciers and rapid ice motion, significant differences were noted. This was highlighted by a detailed comparison of the bed topography around the northeast Greenland ice stream.

Greenland land-terminating glaciers velocity trends during the last two decades

2021 ◽  
Author(s):  
Paul Halas ◽  
Jeremie Mouginot ◽  
Basile de Fleurian ◽  
Petra Langebroek
Keyword(s):  
Water Pressure ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Melting ◽  
Limited Area ◽  
Ice Dynamics ◽  
Basal Sliding ◽  
Surface Melt ◽  
Ice Sheet Dynamics ◽  
The Impact

<div> <p>Ice losses from the Greenland Ice Sheet have been increasing in the last two decades, leading to a larger contribution to the global sea level rise. Roughly 40% of the contribution comes from ice-sheet dynamics, mainly regulated by basal sliding. The sliding component of glaciers has been observed to be strongly related to surface melting, as water can eventually reach the bed and impact the subglacial water pressure, affecting the basal sliding.  </p> </div><div> <p>The link between ice velocities and surface melt on multi-annual time scale is still not totally understood even though it is of major importance with expected increasing surface melting. Several studies showed some correlation between an increase in surface melt and a slowdown in velocities, but there is no consensus on those trends. Moreover those investigations only presented results in a limited area over Southwest Greenland.  </p> </div><div> <p>Here we present the ice motion over many land-terminating glaciers on the Greenland Ice Sheet for the period 2000 - 2020. This type of glacier is ideal for studying processes at the interface between the bed and the ice since they are exempted from interactions with the sea while still being relevant for all glaciers since they share the same basal friction laws. The velocity data was obtained using optical Landsat 7 & 8 imagery and feature-tracking algorithm. We attached importance keeping the starting date of our image pairs similar, and avoided stacking pairs starting before and after melt seasons, resulting in multiple velocity products for each year.  </p> </div><div> <p>Our results show similar velocity trends for previously studied areas with a slowdown until 2012 followed by an acceleration. This trend however does not seem to be observed on the whole ice sheet and is probably specific to this region’s climate forcing. </p> </div><div> <p>Moreover comparison between ice velocities from different parts of Greenland allows us to observe the impact of different climatic trends on ice dynamics.</p> </div>

Early Holocene ocean conditions off the Zachariæ Isstrøm, Northeast Greenland

2021 ◽  
Author(s):  
Joanna Davies ◽  
Anders Møller Mathiasen ◽  
Kristiane Kristensen ◽  
Christof Pearce ◽  
Marit-Solveig Seidenkrantz
Keyword(s):  
Climate Change ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atlantic Water ◽  
The Arctic ◽  
Future Climate Change ◽  
Polar Regions ◽  
Ice Shelf ◽  
Outlet Glacier ◽  
The Impact

<p>The polar regions exhibit some of the most visible signs of climate change globally; annual mass loss from the Greenland Ice Sheet (GrIS) has quadrupled in recent decades, from 51 ± 65 Gt yr<sup>−1</sup> (1992-2001) to 211 ± 37 Gt yr<sup>−1</sup> (2002-2011). This can partly be attributed to the widespread retreat and speed-up of marine-terminating glaciers. The Zachariae Isstrøm (ZI) is an outlet glacier of the Northeast Greenland Ice Steam (NEGIS), one of the largest ice streams of the GrIS (700km), draining approximately 12% of the ice sheet interior. Observations show that the ZI began accelerating in 2000, resulting in the collapse of the floating ice shelf between 2002 and 2003. By 2014, the ice shelf extended over an area of 52km<sup>2</sup>, a 95% decrease in area since 2002, where it extended over 1040km<sup>2</sup>. Paleo-reconstructions provide an opportunity to extend observational records in order to understand the oceanic and climatic processes governing the position of the grounding zone of marine terminating glaciers and the extent of floating ice shelves. Such datasets are thus necessary if we are to constrain the impact of future climate change projections on the Arctic cryosphere.</p><p>A multi-proxy approach, involving grain size, geochemical, foraminiferal and sedimentary analysis was applied to marine sediment core DA17-NG-ST8-92G, collected offshore of the ZI, on  the Northeast Greenland Shelf. The aim was to reconstruct changes in the extent of the ZI and the palaeoceanographic conditions throughout the Early to Mid Holocene (c.a. 12,500-5,000 cal. yrs. BP). Evidence from the analysis of these datasets indicates that whilst there has been no grounded ice at the site over the last 12,500 years, the ice shelf of the ZI extended as a floating ice shelf over the site between 12,500 and 9,200 cal. yrs. BP, with the grounding line further inland from our study site. This was followed by a retreat in the ice shelf extent during the Holocene Thermal Maximum; this was likely to have been governed, in part, by basal melting driven by Atlantic Water (AW) recirculated from Svalbard or from the Arctic Ocean. Evidence from benthic foraminifera suggest that there was a shift from the dominance of AW to Polar Water at around 7,500 cal. yrs. BP, although the ice shelf did not expand again despite of this cooling of subsurface waters.</p>

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