Is the impact of climate oscillations changing over the Greenland Ice Sheet?

2021 ◽  
Author(s):  
Tiago Silva ◽  
Jakob Abermann ◽  
Sonika Shahi ◽  
Wolfgang Schöner ◽  
Brice Nöel
Keyword(s):  
North Atlantic ◽  
General Circulation ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Energy Budget ◽  
Climate Indices ◽  
Near Surface ◽  
Climate Oscillations ◽  
Regional Climate Model Output ◽  
The Impact

<p>Greenland Block Index (GBI) and North Atlantic Oscillation (NAO) are climate indices widely used for climatological studies especially over the Greenland Ice Sheet (GrIS). Particularly in summer, they are highly and negatively correlated; both have a strong relationship to near surface processes around the GrIS; their magnitude creates non-linear feedbacks and influences the low troposphere, shaping spatial accumulation and ablation patterns.</p><p>NAO is a measure of the surface pressure difference over the North Atlantic, providing insight of intensity and location of the jet stream. GBI denotes the general circulation over Greenland at the 500-hPa level and depending on its signal promotes heat and moist advection towards inland.</p><p>Based on the 1959-2019 period, the extreme summer melt of 2019 recorded the highest mean summer GBI while the extreme summer melt of 2012 recorded the lowest mean summer NAO. Their impact, however, goes beyond the melting season since the inter-seasonal phase change of these two indices may enhance/ postpone early melt/late refreezing and vice-versa.</p><p>Supported by 62 years of high-resolution regional climate model output (RACMO2.3p2), this work uses a statistical approach to analyze inter-seasonal variability of climate oscillations and their impact on the surface energy budget components over the GrIS. Also, teleconnection changes in a changing climate are hypothesized.</p>

scholarly journals Large sensitivity of a Greenland ice sheet model to atmospheric forcing fields

2012 ◽  
Vol 6 (2) ◽  
pp. 1037-1083 ◽  
Author(s):  
A. Quiquet ◽  
H. J. Punge ◽  
C. Ritz ◽  
X. Fettweis ◽  
M. Kageyama ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Global Climate Models ◽  
Near Surface ◽  
Temperature And Precipitation ◽  
The Impact

Abstract. The prediction of future climate and ice sheet evolution requires coupling of ice sheet and climate models. Before proceeding to a coupled setup, we propose to analyze the impact of model simulated climate on an ice sheet. Here, we undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary condition to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyr of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed ones, there are considerable deviations among the ice sheets on regional scales. These can be explained by difficulties in modelling local temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations of each climate model are also due to the differences in the atmospheric general circulation. In the context of coupling ice sheet and climate models, we conclude that appropriate downscaling methods will be needed and systematic corrections of the climatic variables at the interface may be required in some cases to obtain realistic results for the Greenland ice sheet (GIS).

scholarly journals Sensitivity of a Greenland ice sheet model to atmospheric forcing fields

2012 ◽  
Vol 6 (5) ◽  
pp. 999-1018 ◽  
Author(s):  
A. Quiquet ◽  
H. J. Punge ◽  
C. Ritz ◽  
X. Fettweis ◽  
H. Gallée ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Global Climate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Global Climate Models ◽  
Near Surface ◽  
Temperature And Precipitation ◽  
The Impact

Abstract. Predicting the climate for the future and how it will impact ice sheet evolution requires coupling ice sheet models with climate models. However, before we attempt to develop a realistic coupled setup, we propose, in this study, to first analyse the impact of a model simulated climate on an ice sheet. We undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary conditions to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyrs of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed one, there are considerable deviations among the ice sheets on regional scales. These deviations can be explained by biases in temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations between the climate models are also due to the differences in the atmospheric general circulation. To account for these differences in the context of coupling ice sheet models with climate models, we conclude that appropriate downscaling methods will be needed. In some cases, systematic corrections of the climatic variables at the interface may be required to obtain realistic results for the Greenland ice sheet (GIS).

Greenland melting signatures in model simulations and oceanic observations

2021 ◽  
Author(s):  
Sophie Stolzenberger ◽  
Roelof Rietbroek ◽  
Claudia Wekerle ◽  
Bernd Uebbing ◽  
Jürgen Kusche
Keyword(s):  
North Atlantic ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ocean Model ◽  
Freshwater Flux ◽  
Model Simulations ◽  
The North ◽  
Sea Level Anomalies ◽  
The North Atlantic ◽  
The Impact

<p>The impact of Greenland freshwater on oceanic variables in the North Atlantic has been controversially discussed in the past. Within the framework of the German research project GROCE (Greenland Ice Sheet Ocean Interaction), we present a comprehensive study using ocean modelling results including and excluding the Greenland freshwater flux. The aim of this study is whether signatures of Greenland ice sheet melting found in ocean model simulations are visible in the observations. Therefore, we estimate changes in temperature, salinity, steric heights and sea level anomalies since the 1990s. The observational database includes altimetric and gravimetric satellite data as well as Argo floats. We will discuss similarities/differences between model simulations and observations for smaller regions around Greenland in the North Atlantic. As these experiments are available for two different horizontal resolutions, we will furthermore be able to assess the effects of an increased model resolution.</p>

scholarly journals Southeast Greenland Winter Precipitation Strongly Linked to the Icelandic Low Position

2018 ◽  
Vol 31 (11) ◽  
pp. 4483-4500 ◽  
Author(s):  
Mira Berdahl ◽  
Asa Rennermalm ◽  
Arno Hammann ◽  
John Mioduszweski ◽  
Sultan Hameed ◽  
...  
Keyword(s):  
Mass Balance ◽  
North Atlantic ◽  
Ice Sheet ◽  
Climate Indices ◽  
Intensity Increase ◽  
The North ◽  
Regional Climate Model Output ◽  
Ice Sheet Mass Balance ◽  
The North Atlantic ◽  
Icelandic Low

Abstract Greenland’s largest precipitation flux occurs in its southeast (SE) region during the winter, controlled primarily by easterly winds and frequent cyclogenesis in the North Atlantic. Several studies have attempted to link SE Greenland precipitation to the North Atlantic Oscillation (NAO) but results are inconsistent. This work uses reanalysis, automatic weather station data, and regional climate model output to show that the east–west position of the Icelandic low is a better predictor of SE Greenland precipitation (average correlation of r = −0.48 in DJF) than climate indices such as the NAO (r = −0.06 in DJF). In years when the Icelandic low is positioned extremely west, moisture transport increases up to ~40% (or up to 40 kg m−1 s−1) off the SE Greenland coast compared to when the low is in an extreme east position. Furthermore, in years when the Icelandic low is positioned extremely west, storm track density and intensity increase just off the SE coast of Greenland. Thus, the Icelandic low’s longitudinal position dominates SE Greenland ice sheet’s wintertime precipitation, a positive term in the ice sheet mass balance. Given SE Greenland’s importance in the overall ice sheet mass balance, the position of the Icelandic low is therefore important for making projections of future sea level.

scholarly journals Short-term impacts of enhanced Greenland freshwater fluxes in an eddy-permitting ocean model

2009 ◽  
Vol 6 (3) ◽  
pp. 2911-2937 ◽  
Author(s):  
R. Marsh ◽  
D. Desbruyères ◽  
J. L. Bamber ◽  
B. A. de Cuevas ◽  
A. C. Coward ◽  
...  
Keyword(s):  
General Circulation ◽  
Mixed Layer Depth ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Circulation Model ◽  
Cyclonic Circulation ◽  
Freshwater Flux ◽  
Sensitivity Experiment ◽  
Freshwater Fluxes ◽  
The Impact

Abstract. In a sensitivity experiment, an eddy-permitting ocean general circulation model is forced with freshwater fluxes from the Greenland Ice Sheet, averaged for the period 1991–2000. The fluxes are obtained with a mass balance model for the ice sheet, forced with the ERA-40 reanalysis dataset. The freshwater flux is distributed around Greenland as an additional term in prescribed runoff, representing seasonal melting of the ice sheet and a fixed year-round iceberg calving flux, for 8.5 model years. The impacts on regional hydrography and circulation are investigated by comparing the sensitivity experiment to a control experiment, without Greenland fluxes. By the end of the sensitivity experiment, the majority of additional fresh water has accumulated in Baffin Bay, and only a small fraction has reached the interior of the Labrador Sea, where winter mixed layer depth is sensitive to small changes in salinity. As a consequence, the impact on large-scale circulation is very slight. An indirect impact of strong freshening off the west coast of Greenland is a small anti-cyclonic circulation around Greenland which opposes the wind-driven cyclonic circulation and reduces net southward flow through the Canadian Archipelago by ~10%. Implications for the post-2000 acceleration of Greenland mass loss are discussed.

Correlated Fluctuations in Surface Melting and Ku-band Radar Penetration in West Central Greenland

2020 ◽  
Author(s):  
Inès Otosaka ◽  
Andrew Shepherd ◽  
Tânia Casal ◽  
Alex Coccia ◽  
Alessandro di Bella ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Radar Data ◽  
Airborne Radar ◽  
Snow Surface ◽  
Near Surface ◽  
Ka Band ◽  
The Impact ◽  
Good Agreement ◽  
Ku Band

<p>Melting at the surface of the Greenland ice sheet has significantly increased since the early 1990s and this affects the degree to which radar sensors can penetrate beyond the snow surface. Indeed, radars are sensitive to changes in the surface and subsurface properties, up to ~15 m below the snow surface for instruments using the Ku-band (13.5 GHz). When melting occurs, meltwater can percolate in the snowpack or refreeze at the surface and in turn, the degree of radar penetration is sharply reduced. Here we use measurements of near-surface density from firn cores and models and airborne radar and laser data collected during the European Space Agency of ESA’s CRYOsat Validation EXperiment (CRYOVEX) campaigns along a 675 km transect in West Central Greenland between 2006 and 2017 to examine spatial and temporal fluctuations in the near-surface properties and how this affects radar measurements. From airborne data acquired with ASIRAS at Ku-band, we identify internal layers corresponding to melt layers in the snowpack down to 15 m, in good agreement with a firn densification model. We examine the spatial and temporal distribution of these melt layers and we find that the abundance of melt layers is increasing with elevation and depicts a strong inter-annual variability and that these fluctuations are correlated with fluctuations in the degree of the radar penetration depth. For instance, in 2012, the Greenland ice sheet experienced unprecedented melting and this is seen in the radar data by a reduction of 70% of the penetration in the snowpack following this event. The 2012 melt layer is still visible in data recorded 5 years after the melt event at a depth of 5.1 m.  As the frequency and extent of extreme melt events is likely to increase in the coming decades, the effects of fluctuations in Ku-band radar penetration are an important consideration for satellite radar altimetry studies.  However, we show that despite large fluctuations in volume scattering, there is a good agreement between Ku-band retracked heights and coincident laser measurements of 13.9 ± 19.9 cm using a threshold retracker. Finally, we also investigate the potential of using higher-frequency KAREN Ka-band (34.5 GHz) airborne radar data to limit the impact of temporal variations in the snowpack properties on backscattered power. We show that surface scattering dominates the Ka-band radar echoes and, overall, they penetrate to significantly lower distances into the near-surface firn by comparison to those acquired at Ku-band. This suggests that Ka-band data are less sensitive to extreme melt events and that the impact of such events on Ka-band data are likely to last for a shorter period of time compared to Ku-band data.</p>

scholarly journals Firn cold content evolution at nine sites on the Greenland ice sheet between 1998 and 2017

2020 ◽  
Vol 66 (258) ◽  
pp. 591-602 ◽  
Author(s):  
B. Vandecrux ◽  
R. S. Fausto ◽  
D. van As ◽  
W. Colgan ◽  
P. L. Langen ◽  
...  
Keyword(s):  
Pore Space ◽  
Ice Sheet ◽  
Thermal Characteristics ◽  
Greenland Ice Sheet ◽  
Surface Energy Budget ◽  
Main Process ◽  
Near Surface ◽  
Climatological Data ◽  
Meltwater Runoff ◽  
Lower Elevation

AbstractCurrent sea-level rise partly stems from increased surface melting and meltwater runoff from the Greenland ice sheet. Multi-year snow, also known as firn, covers about 80% of the ice sheet and retains part of the surface meltwater. Since the firn cold content integrates its physical and thermal characteristics, it is a valuable tool for determining the meltwater-retention potential of firn. We use gap-filled climatological data from nine automatic weather stations in the ice-sheet accumulation area to drive a surface-energy-budget and firn model, validated against firn density and temperature observations, over the 1998–2017 period. Our results show a stable top 20 m firn cold content (CC20) at most sites. Only at the lower-elevation Dye-2 site did CC20 decrease, by 24% in 2012, before recovering to its original value by 2017. Heat conduction towards the surface is the main process feeding CC20 at all nine sites, while CC20 reduction occurs through low-cold-content fresh-snow addition at the surface during snowfall and latent-heat release when meltwater refreezes. Our simulations suggest that firn densification, while reducing pore space for meltwater retention, increases the firn cold content, enhances near-surface meltwater refreezing and potentially sets favourable conditions for ice-slab formation.

scholarly journals The impact of different glacial boundary conditions on atmospheric dynamics and precipitation in the North Atlantic region

2012 ◽  
Vol 8 (1) ◽  
pp. 63-101
Author(s):  
D. Hofer ◽  
C. C. Raible ◽  
A. Dehnert ◽  
J. Kuhlemann
Keyword(s):  
Boundary Conditions ◽  
North Atlantic ◽  
General Circulation ◽  
Ice Sheet ◽  
Atmospheric Dynamics ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The North ◽  
The North Atlantic ◽  
The Impact

Abstract. Using a highly resolved atmospheric general circulation model the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Seven 30-yr time slice experiments of the Last Glacial Maximum (21 ka ago) and of a less pronounced glacial state – the Middle Weichselian (65 ka ago) – are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing, and in the prescribed time-varying lower boundary conditions, which are taken from a lower-resolved but fully-coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A large altitude of this ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying lower boundary conditions – evaluated using two simulations of the Last Glacial Maximum with a global mean temperature difference of 1.1 °C – are of second order compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner as the topographic changes.

scholarly journals The impact of different glacial boundary conditions on atmospheric dynamics and precipitation in the North Atlantic region

2012 ◽  
Vol 8 (3) ◽  
pp. 935-949 ◽  
Author(s):  
D. Hofer ◽  
C. C. Raible ◽  
A. Dehnert ◽  
J. Kuhlemann
Keyword(s):  
North Atlantic ◽  
General Circulation ◽  
Ice Sheet ◽  
Atmospheric Dynamics ◽  
Laurentide Ice Sheet ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The North ◽  
The North Atlantic ◽  
The Impact

Abstract. Using a highly resolved atmospheric general circulation model, the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Six 30-yr time slice experiments of the Last Glacial Maximum at 21 thousand years before the present (ka BP) and of a less pronounced glacial state – the Middle Weichselian (65 ka BP) – are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing and in the prescribed time-varying sea surface temperature and sea ice, which are taken from a lower-resolved, but fully coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A high surface elevation of the Laurentide ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying sea surface temperatures and sea ice are of second order importance compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner compared with the topographic changes.

Sign in / Sign up

Export Citation Format

Share Document