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  • 1
    Online Resource
    Online Resource
    BMBF Förderinitiative Paläo Modellierung (PalMod) : Vorhaben (Verbund) PalMod-1-3: Lange transiente Simulationen : Abschlussbericht : Laufzeit: 01.08.2015-30.04.2021 (2021)
    Bremerhaven : Alfred-Wegener-Institut (AWI) Helmholtz-Zentrum für Polar- und Meeresforschung
    Details Availability
    Keywords: Forschungsbericht ; Pleistozän ; Paläoklima ; Modell ; Simulation ; Meer ; Kohlenstoffkreislauf
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (15 Seiten, 223,21 KB)
    URL: https://doi.org/10.2314/KXP:1828248134
    DOI: 10.2314/KXP:1828248134
    Language: German , English
    Note: Förderkennzeichen BMBF 01LP1504A-D , Verbundnummer 01162215 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Literaturangaben , Sprache der Kurzfassungen: Deutsch, Englisch
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  • 2
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    Last glacial inception trajectories for the Northern Hemisphere from coupled ice and climate modelling (2021)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: We present an ensemble of last glacial inception (LGI) simulations for the Northern Hemisphere that captures a significant fraction of inferred ice volume changes within proxy uncertainties. This ensemble was performed with LCice 1.0, a coupled ice sheet and climate model, varying parameters of both climate and ice sheet components, as well as the coupling between them. Certain characteristics of the spatiotemporal pattern of ice growth and subsequent retreat in both North America (NA) and Eurasia (EA) are sensitive to parameter changes while others are not. We find that the initial inception of ice over NA and EA is best characterized by the nucleation of ice at high-latitude and high-elevation sites. Subsequent spreading and merger along with large-scale conversion of snowfields dominate in different sectors. The latter plays an important role in the merging of eastern and western ice regions in NA. The inception peak ice volume in the ensemble occurs approximately at 111 ka and therefore lags the summer 60∘ N insolation minimum by more than 3 kyr. Ice volumes consistently peak earlier over EA than NA. The inception peak in North America is characterized by a merged Laurentide and Cordilleran ice sheet, with the Davis Strait covered in ice in ∼80 % of simulations. Ice also bridges Greenland and Iceland in all runs by 114 ka and therefore blocks the Denmark Strait. This latter feature would thereby divert the East Greenland Current and Denmark Strait overflow with a potentially significant impact on ocean circulation. The Eurasian ice sheet at its inception peak varies across ensemble runs between a continuous ice sheet and multiple smaller ice caps. In both continents, the colder high latitudes (i.e. Ellesmere and Svalbard) tend to grow ice through the entire simulation (to 102 ka), while lower latitudes lose ice after ∼110 ka. We find temperature decreases over the initial phases of the inception lead to the expansion of NA ice sheet area and that subsequent precipitation increases contribute to its thickening. EA ice sheet area also expands with decreasing temperatures, but sea ice limits any increases in precipitation, leading to an earlier retreat away from the EA maximum ice sheet volume. We also examine the extent to which the capture of both LGI ice growth and retreat constrains the coupled ice–climate model sensitivity to changing atmospheric pCO2. The 55-member sub-ensemble that meets our criteria for “acceptable” ice growth and retreat has an equilibrium climate sensitivity lower bound that is 0.3 ∘C higher than that of the full ensemble. This suggests some potential value of fully coupled ice–climate modelling of the last glacial inception to constrain future climate change.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Projected land ice contributions to twenty-first-century sea level rise (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: The land ice contribution to global mean sea level rise has not yet been predicted1 using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models2,3,4,5,6,7,8, but primarily used previous-generation scenarios9 and climate models10, and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios11,12 using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Ice sheet decline and rising atmospheric CO2 control AMOC sensitivity to deglacial meltwater discharge (2022)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: Highlights: • Climate model sensitivity experiments are performed using state-of-the-art ice sheet and freshwater reconstructions • Declining Northern Hemisphere ice sheets increase the sensitivity of the AMOC to North Atlantic meltwater discharge • Deglacial rise in atmospheric CO2 concentration decreases the sensitivity of the AMOC to North Atlantic meltwater discharge • Both effects provide a complementary perspective to existing explanations for abrupt AMOC transitions Abstract: The last deglaciation was characterized by a sequence of abrupt climate events thought to be linked to rapid changes in Atlantic meridional overturning circulation (AMOC). The sequence includes a weakening of the AMOC after the Last Glacial Maximum (LGM) during Heinrich Stadial 1 (HS1), which ends with an abrupt AMOC amplification at the transition to the Bølling/Allerød (B/A). This transition occurs despite persistent deglacial meltwater fluxes that counteract vigorous North Atlantic deep-water formation. Using the Earth system model COSMOS with a range of deglacial boundary conditions and reconstructed deglacial meltwater fluxes, we show that deglacial CO2 rise and ice sheet decline modulate the sensitivity of the AMOC to these fluxes. While declining ice sheets increase the sensitivity, increasing atmospheric CO2 levels tend to counteract this effect. Therefore, the occurrence of a weaker HS1 AMOC and an abrupt AMOC increase in the presence of meltwater, might be explained by these effects, as an alternative to or in combination with changes in the magnitude or routing of meltwater discharge.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    LM17.3 - a global vertical land motion model of glacial isostatic adjustment (2021)
    PANGAEA
    Details
    Publication Date: 2024-04-20
    Description: We provide a global 0.5-degree grid of vertical land motion (in mm/a) of the LM17.3 glacial isostatic adjustment (GIA) model. The radially varying earth model part is profile VM5a (Peltier et al. 2015). The ice load is different to any other GIA model and combines regional ice loads without taking care of balancing the global sea-level equivalent of all ice sheets and glaciers with that expected from paleo-sea-level indicators. The regional models are: * GLAC-1D for North America (Tarasov et al. 2012), * HUY3 for Greenland (Lecavalier et al. 2014), * GLAC #71340 for Fennoscandia/Barents Sea (Tarasov et al., 2014), * ANU-ICE for Iceland, High Mountain Areas, Siberian Mountains and Tibet (Lambeck et al. 2014), * IJ04_Patagonia for Patagonia (updated from Ivins & James 2004), * ICE-6G_C for New Zealand (Argus et al. 2014, Peltier et al. 2015), * GLAC-1D for Antarctica (Briggs et al. 2014). Additional models (W12, Whitehouse et al. 2012, and IJ05_R2, Ivins et al. 2013, for Antarctica; ANU-ICE, Lambeck et al. 2017, and NAIce, Gowan et al. 2016, for North America) were tested in the development of the model but not used in the end. Little ice age is not included nor any ice mass change during the last 100 years. The eustatic sea-level equivalent at last glacial maximum amounts to 113.8 m for all ice sheets and glaciers together. Because we use an ice model that has not been tuned to fit global constraints, it may highlight areas which cannot match commonly used GIA observations. However, we note that the earth model used in our calculations is different to the earth model used in the development of some regional ice models, e.g. HUY3, ANU-ICE, IJ04_Patagonia (see respective references), thus some differences can be related to this. The LM17.3 model was introduced in Jäggi et al. (2019), and its DDK5-filtered geoid and water heights can be found in the EGSIEM plotter (http://plot.egsiem.eu/index.php?p=timeseries). The GIA model uses material compressibility and includes time-dependent coastlines and rotational feedback. The vertical land motion can be used/tested in sea-level investigations and projections. Work towards a model that incorporates 3D earth structure, and an updated ice model, is ongoing.
    Keywords: EGSIEM; European Gravity Service for Improved Emergency Management; glacial isostatic adjustment; sea level
    Type: Dataset
    Format: application/zip, 1.9 MBytes
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    DATA PANGAEA
  • 6
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    Ice sheet decline and rising atmospheric CO2 control AMOC sensitivity to deglacial meltwater discharge (2022)
    Elsevier
    In:  EPIC3Global and Planetary Change, Elsevier, 210, pp. 103755-103755, ISSN: 0921-8181
    Details
    Publication Date: 2023-09-19
    Description: The last deglaciation was characterized by a sequence of abrupt climate events thought to be linked to rapid changes in Atlantic meridional overturning circulation (AMOC). The sequence includes a weakening of the AMOC after the Last Glacial Maximum (LGM) during Heinrich Stadial 1 (HS1), which ends with an abrupt AMOC amplification at the transition to the Bølling/Allerød (B/A). This transition occurs despite persistent deglacial meltwater fluxes that counteract vigorous North Atlantic deep-water formation. Using the Earth system model COSMOS with a range of deglacial boundary conditions and reconstructed deglacial meltwater fluxes, we show that deglacial CO2 rise and ice sheet decline modulate the sensitivity of the AMOC to these fluxes. While declining ice sheets increase the sensitivity, increasing atmospheric CO2 levels tend to counteract this effect. Therefore, the occurrence of a weaker HS1 AMOC and an abrupt AMOC increase in the presence of meltwater, might be explained by these effects, as an alternative to or in combination with changes in the magnitude or routing of meltwater discharge.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 7
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    Mass balance of the Greenland Ice Sheet from 1992 to 2018 (2021)
    Nature P.G.
    Details
    Publication Date: 2024-01-18
    Description: The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades, and it is expected to continue to be so. Although increases in glacier flow and surface melting have been driven by oceanic and atmospheric warming, the magnitude and trajectory of the ice sheet’s mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 ± 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 ± 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 ± 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 ± 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 ± 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 ± 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions and ocean temperatures fell at the terminus of Jakobshavn Isbræ. Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario, which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.
    Description: Published
    Description: 233–239
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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