Sensitivity of the Greenland Ice Sheet to Interglacial Climate Forcing: MIS 5e Versus MIS 11

Rachmayani, Rima; Prange, Matthias; Lunt, Daniel J.; Stone, E. J.; Schulz, Michael

doi:10.1002/2017pa003149

Cited by 16 publications

(21 citation statements)

References 91 publications

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“…The ice age cycles have been forced by features of Earth's orbit (Milankovitch cycling), which do not repeat exactly. To test the influence of the unique details, Rachmayani et al () forced the ice sheet model Glimmer with GCM time‐slice climate simulations for MIS 5e and 11. They found greater effect of warming on GIS during MIS 11 because of stronger oceanic heat transport in the Atlantic meridional overturning circulation, in response to stronger North Atlantic Deep Water formation caused by stronger wind‐driven salt transport.…”

Section: Hypotheses For Gis Holocene Near‐stability Yet Pleistocene Nmentioning

confidence: 99%

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

et al. 2019

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The history of the Greenland Ice Sheet has been influenced by the geodynamic response to ice sheet fluctuations, and this interaction may help explain past deglaciations under modest climate forcing. We hypothesize that when the Iceland hot spot passed beneath north-central Greenland, it thinned the lithosphere and left anomalous heat likely with partially melted rock; however, it did not break through the crust to supply voluminous flood basalts. Subsequent Plio-Pleistocene glacial-interglacial cycles caused large and rapidly migrating stresses, driving dike formation and other processes that shifted melted rock toward the surface. The resulting increase in surface geothermal flux favored a thinner, faster-responding ice sheet that was more prone to deglaciation. If this hypothesis of control through changes in geothermal flux is correct, then the long-term (10 5 to 10 6 years) trend now is toward lower geothermal flux, but with higher-frequency (≤10 4 to 10 5 years) oscillations linked to glacial-interglacial cycles. Whether the geothermal flux is increasing or decreasing now is not known but is of societal relevance due to its possible impact on ice flow. We infer that projections of the future of the ice sheet and its effect on sea level must integrate geologic and geophysical data as well as glaciological, atmospheric, oceanic, and paleoclimatic information.Plain Language Summary The behavior of the Greenland Ice Sheet and its effect on future sea level depends on its geologic history as well as on greenhouse warming. The Iceland hot spot passed beneath Greenland millions of years ago, and left hot, possibly melted rock deep beneath the island. Since then, growth and shrinkage of the ice sheet have changed stresses in the rocks beneath. These stress changes may have shifted the melted rock upward, perhaps all the way to the base of the ice sheet, probably in pulses tied to times of rapid ice sheet change. This would have changed the heat flow from the Earth into the base of the ice, which affects how easily the ice sheet grows and shrinks. The future of the ice sheet depends primarily on how much the climate warms, but better understanding of the interactions between the ice and the rocks beneath will allow better predictions of ice sheet changes.

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Section: Hypotheses For Gis Holocene Near‐stability Yet Pleistocene Nmentioning

confidence: 99%

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

et al. 2019

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“…Simulating past climates has been instrumental in improving our understanding of the mechanisms of climate change (e.g. Gates, 1976;Haywood et al, 2016;Jungclaus et al, 2017;Kageyama et al, 2017Kageyama et al, , 2018Kohfeld et al, 2013;Lunt et al, 2008;Otto-Bliesner et al, 2017;Ramstein et al, 1997), as well as in identifying and assessing discrepancies in palaeoclimate reconstructions (e.g. Rind and Peteet, 1985).…”

Section: Introductionmentioning

confidence: 99%

CMIP6/PMIP4 simulations of the mid-Holocene and Last Interglacial using HadGEM3: comparison to the pre-industrial era, previous model versions and proxy data

et al. 2020

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Abstract. Palaeoclimate model simulations are an important tool to improve our understanding of the mechanisms of climate change. These simulations also provide tests of the ability of models to simulate climates very different to today. Here we present the results from two brand-new simulations using the latest version of the UK's physical climate model, HadGEM3-GC3.1; they are the mid-Holocene (∼6 ka) and Last Interglacial (∼127 ka) simulations, both conducted under the auspices of CMIP6/PMIP4. This is the first time this version of the UK model has been used to conduct palaeoclimate simulations. These periods are of particular interest to PMIP4 because they represent the two most recent warm periods in Earth history, where atmospheric concentration of greenhouse gases and continental configuration are similar to the pre-industrial period but where there were significant changes to the Earth's orbital configuration, resulting in a very different seasonal cycle of radiative forcing. Results for these simulations are assessed firstly against the same model's pre-industrial control simulation (a simulation comparison, to describe and understand the differences between the pre-industrial – PI – and the two palaeo simulations) and secondly against previous versions of the same model relative to newly available proxy data (a model–data comparison, to compare all available simulations from the same model with proxy data to assess any improvements due to model advances). The introduction of this newly available proxy data adds further novelty to this study. Globally, for metrics such as 1.5 m temperature and surface rainfall, whilst both the recent palaeoclimate simulations are mostly capturing the expected sign and, in some places, magnitude of change relative to the pre-industrial, this is geographically and seasonally dependent. Compared to newly available proxy data (including sea surface temperature – SST – and rainfall) and also incorporating data from previous versions of the model shows that the relative accuracy of the simulations appears to vary according to metric, proxy reconstruction used for comparison and geographical location. In some instances, such as mean rainfall in the mid-Holocene, there is a clear and linear improvement, relative to proxy data, from the oldest to the newest generation of the model. When zooming into northern Africa, a region known to be problematic for models in terms of rainfall enhancement, the behaviour of the West African monsoon in both recent palaeoclimate simulations is consistent with current understanding, suggesting a wetter monsoon during the mid-Holocene and (more so) the Last Interglacial, relative to the pre-industrial era. However, regarding the well-documented “Saharan greening” during the mid-Holocene, results here suggest that the most recent version of the UK's physical model is still unable to reproduce the increases suggested by proxy data, consistent with all other previous models to date.

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Section: Freshwater Sourcesmentioning

confidence: 99%

“…Landscape reconstructions (Bierman et al, 2014) and numerical simulations (Rachmayani et al, 2017;Robinson et al, 2017) indicate that northern Greenland also experienced considerable melting during MIS 11. This increased melting may have been further enhanced by a stronger AMOC responsible for additional northward heat transport (Rachmayani et al, 2017). The deposition of meltwater masses derived from northern Greenland in the Nordic Seas is conceivable under reconstructed atmospheric circulation patterns (Kandiano et al, 2012), and might help to explain the delayed SST optima relative to the insolation peak (Figure 7).…”

Section: Freshwater Sourcesmentioning

confidence: 99%

Cold Water in a Warm World: Investigating the Origin of the Nordic Seas' Unique Surface Properties During MIS 11

Doherty

Thibodeau

2018

Front. Mar. Sci.

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Surface waters in the Nordic Seas were colder and fresher throughout the marine isotope stage (MIS) 11 interglacial compared to present day. This has been previously attributed to the continuous delivery of freshwater sourced from large ice structures characteristic of the preceding glacial interval, MIS 12. While it is conventionally believed that high-latitude surface freshening can trigger a reduction of the Atlantic Meridional Overturning Circulation (AMOC), multiple lines of evidence suggest a vigorous AMOC despite elevated freshwater forcing in the Nordic Seas. Here, we review and reanalyze evidence for sea surface properties throughout the Nordic Seas and North Atlantic. We find that surface waters in the Nordic Seas experienced an unusually variable inception of interglacial temperature conditions with multiple high-magnitude cold excursions. While cold events in the North Atlantic were frequently associated with in situ meltwater deposition as reconstructed by ice-rafted debris, this proxy was virtually uncorrelated with cold events in the Nordic Seas. Additionally, stable nitrogen analysis revealed variable levels of nutrient utilization in the Nordic Seas' surface layer throughout MIS 11. This may reflect a dynamic structure of the upper ocean concomitant with an intermittent rate of freshwater delivery. Based on this combination of evidence, we suggest that the colder and fresher surface layer in the Nordic Seas was supplied from higher latitudes, rather than from locally-sourced iceberg meltwater as is characteristic of North Atlantic forcing. Pairing proxy-based evidence with recent numerical simulations further decouples surface freshening in the Nordic Seas and Greenland meltwater input, discrediting Greenland as a source of freshwater to this region during the later phase of MIS 11. Because the origin of freshwater has implications for its rate of delivery, our study might help to explain the active AMOC despite surface freshening during MIS 11 and should be recognized when considering this interglacial as an analog for near-future climate change scenarios.

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Sensitivity of the Greenland Ice Sheet to Interglacial Climate Forcing: MIS 5e Versus MIS 11

Cited by 16 publications

References 91 publications

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

CMIP6/PMIP4 simulations of the mid-Holocene and Last Interglacial using HadGEM3: comparison to the pre-industrial era, previous model versions and proxy data

Cold Water in a Warm World: Investigating the Origin of the Nordic Seas' Unique Surface Properties During MIS 11

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