Circumpolar Distribution of Holocene Marine Fossils in Antarctic Beaches

AbstractThe composite frequency of radiocarbon ages for Holocene marine fossils from beaches around Antarctica is significantly different than random. Variations in the frequency of fossil ages coincide with the timing of Holocene climate changes inferred from Antarctic ice cores, sub-Antarctic lakes, polar and alpine moraines, and sea level. Extant Antarctic marine species that occur as fossils in beaches may reflect coastal meltwater impacts associated with ice sheet marginal fluctuations that were circumpolar during the Holocene.

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Impact of relative sea level and rapid climate changes on the architecture and lithofacies of the Holocene Rhone subaqueous delta (Western Mediterranean Sea)

Sedimentary Geology ◽

10.1016/j.sedgeo.2014.02.004 ◽

2014 ◽

Vol 305 ◽

pp. 35-53 ◽

Cited By ~ 26

Author(s):

Anne-Sophie Fanget ◽

Serge Berné ◽

Gwénaël Jouet ◽

Maria-Angela Bassetti ◽

Bernard Dennielou ◽

...

Keyword(s):

Mediterranean Sea ◽

Sea Level ◽

Climate Changes ◽

Western Mediterranean ◽

Relative Sea Level ◽

The Holocene ◽

Western Mediterranean Sea

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Quantification of the Greenland ice sheet contribution to Last Interglacial sea level rise

Climate of the Past ◽

10.5194/cp-9-621-2013 ◽

2013 ◽

Vol 9 (2) ◽

pp. 621-639 ◽

Cited By ~ 71

Author(s):

E. J. Stone ◽

D. J. Lunt ◽

J. D. Annan ◽

J. C. Hargreaves

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Climate Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

The Arctic ◽

Substantial Contribution ◽

Interglacial Period ◽

Last Interglacial

Abstract. During the Last Interglacial period (~ 130–115 thousand years ago) the Arctic climate was warmer than today, and global mean sea level was probably more than 6.6 m higher. However, there are large discrepancies in the estimated contributions to this sea level change from various sources (the Greenland and Antarctic ice sheets and smaller ice caps). Here, we determine probabilistically the likely contribution of Greenland ice sheet melt to Last Interglacial sea level rise, taking into account ice sheet model parametric uncertainty. We perform an ensemble of 500 Glimmer ice sheet model simulations forced with climatologies from the climate model HadCM3, and constrain the results with palaeodata from Greenland ice cores. Our results suggest a 90% probability that Greenland ice melt contributed at least 0.6 m, but less than 10% probability that it exceeded 3.5 m, a value which is lower than several recent estimates. Many of these previous estimates, however, did not include a full general circulation climate model that can capture atmospheric circulation and precipitation changes in response to changes in insolation forcing and orographic height. Our combined modelling and palaeodata approach suggests that the Greenland ice sheet is less sensitive to orbital forcing than previously thought, and it implicates Antarctic melt as providing a substantial contribution to Last Interglacial sea level rise. Future work should assess additional uncertainty due to inclusion of basal sliding and the direct effect of insolation on surface melt. In addition, the effect of uncertainty arising from climate model structural design should be taken into account by performing a multi-climate-model comparison.

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Ice-sheet modelling characteristics in sea-level-based temperature reconstructions over the last glacial cycle

Journal of Glaciology ◽

10.3189/172756506781828944 ◽

2006 ◽

Vol 52 (176) ◽

pp. 149-158 ◽

Cited By ~ 3

Author(s):

Frank Wilschut ◽

Richard Bintanja ◽

Roderik S.W. Van De Wal

Keyword(s):

Sea Level ◽

Sediment Cores ◽

Ice Sheet ◽

Ice Cores ◽

Glacial Cycle ◽

Deep Sea Sediment ◽

Last Glacial ◽

Proxy Records ◽

Temperature Reconstructions ◽

The Last Glacial

AbstractA widely used method for investigating palaeotemperatures is to analyze local proxy records (e.g. ice cores or deep-sea sediment cores). The interpretation of these records is often not straightforward, and global or hemispheric means cannot be deduced from local estimates because of large spatial variability. Using a different approach, temperature changes over the last glacial cycle can be estimated from sea-level observations by applying an inverse method to an ice-sheet model. In order to understand the underlying physical mechanisms, we used a 1-D ice-sheet model and a 3-D coupled thermodynamic ice-sheet–ice-shelf–bedrock model to investigate the importance of several physical processes for the inverse temperature reconstructions. Results show that (i) temperature reconstructions are sensitive to the employed formulation of mass balance, (ii) excluding thermodynamics in the ice sheet leads to a smaller temperature amplitude in the reconstruction and (iii) hysteresis in the non-linear relation between sea level and temperature occurs as a consequence of ice redistribution in the process of merging and separation of ice sheets. The ice redistribution does not occur if the geometry does not support the formation of a relatively flat dome, which tends to be preserved in warming conditions.

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Reconciling reconstructions and simulations of the Greenland ice sheet and its climate during the Last Interglacial period

10.5194/egusphere-egu2020-19016 ◽

2020 ◽

Author(s):

Alexander Robinson ◽

Emilie Capron ◽

Jorge Alvarez-Solas ◽

Michael Bender ◽

Heiko Goelzer ◽

...

Keyword(s):

Climate Change ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

Future Climate Change ◽

Interglacial Period ◽

Last Interglacial ◽

Proxy Data ◽

Last Interglacial Period

There is still no consensus concerning the evolution of the Greenland ice sheet during the Last Interglacial period (LIG, 130-115 kyr ago). Ice cores indicate that the ice sheet survived over most of the continent. Proxy data indicate temperature anomalies of up to 6-8&#176;C. However, under these conditions, models predict almost complete deglaciation. This paradox must be resolved to be able to quantify Greenland&#8217;s sea-level contribution during the LIG as well as to understand its sensitivity to future climate change. Here we analyze the available evidence and outline strategies to reconcile modeling and data efforts for Greenland during the LIG.

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Tracing the depth of the Holocene ice in North Greenland from radio-echo sounding data

Annals of Glaciology ◽

10.3189/2013aog64a057 ◽

2013 ◽

Vol 54 (64) ◽

pp. 44-50 ◽

Cited By ~ 25

Author(s):

Nanna B. Karlsson ◽

Dorthe Dahl-Jensen ◽

S. Prasad Gogineni ◽

John D. Paden

Keyword(s):

Ice Core ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

The Holocene ◽

Fitting Method ◽

Radio Echo Sounding ◽

North Greenland ◽

Echo Sounding

Abstract Radio-echo sounding surveys over the Greenland ice sheet show clear, extensive internal layering, and comparisons with age–depth scales from deep ice cores allow for dating of the layering along the ice divide. We present one of the first attempts to extend the dated layers beyond the ice core drill sites by locating the depth of the Bølling–Allerød transition in >400 flight-lines using an automated fitting method. Results show that the transition is located in the upper one-third of the ice column in the central part of North Greenland, while the transition lowers towards the margin. This pattern mirrors the present surface accumulation, and also indicates that a substantial amount of pre-Holocene ice must be present in central North Greenland.

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Antarctic ice volume for the last 740 ka calculated with a simple ice sheet model

Antarctic Science ◽

10.1017/s0954102005002683 ◽

2005 ◽

Vol 17 (2) ◽

pp. 281-287 ◽

Cited By ~ 6

Author(s):

J. OERLEMANS

Keyword(s):

Sea Level ◽

Deep Sea ◽

Relative Phase ◽

Ice Sheet ◽

Ice Cores ◽

Temperature History ◽

Glacial Cycle ◽

Ice Volume ◽

The Antarctic ◽

And Sea Level

Fluctuations in the volume of the Antarctic ice sheet for the last 740 ka are calculated by forcing a simple ice sheet model with a sea-level history (from a composite deep sea δ18O record) and a temperature history (from the Dome C deuterium record). Antarctic ice volume reaches maximum values of about 30 × 1015 m3, 3 to 8 ka after glacial maxima [defined as maximum values of the deep sea δ18O record]. Minimum values of ice volume reached in the course of interglacial periods are about 26 × 1015 m3. Most of the time the temperature forcing (larger accumulation) and sea-level forcing (grounding-line retreat) tend to have competing effects. However, towards the end of a glacial cycle, when temperature rises and sea-level is still relatively low, the ice volume reaches a peak. The peak value is very sensitive to the relative phase of the sea-level forcing with respect to the temperature forcing. This is further studied by looking at the response of the model to purely periodic forcings with different relative phase. The large sensitivity of ice sheet size to the phase of the forcings may have some implications for dating of deep ice cores. Care has to be taken by using anchor points from the deep sea record.

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Review article: Existing and potential evidence for Holocene grounding-line retreat and readvance in Antarctica

10.5194/tc-2021-360 ◽

2021 ◽

Author(s):

Joanne S. Johnson ◽

Ryan A. Venturelli ◽

Greg Balco ◽

Claire S. Allen ◽

Scott Braddock ◽

...

Keyword(s):

Direct Evidence ◽

Sediment Cores ◽

Ice Sheet ◽

Ice Cores ◽

Radar Data ◽

Oceanic Circulation ◽

Surface Mass ◽

The Holocene ◽

Grounding Line ◽

The Antarctic

Abstract. Widespread existing geological records from above the modern ice-sheet surface and outboard of the current ice margin show that the Antarctic Ice Sheet (AIS) was much more extensive at the Last Glacial Maximum (~20 ka) than at present. However, whether it was ever smaller than present during the last few millennia, and (if so) by how much, is known only for a few locations because direct evidence lies within or beneath the ice sheet, which is challenging to access. Here, we describe how retreat and readvance (henceforth “readvance”) of AIS grounding lines during the Holocene could be detected and quantified using subglacial bedrock, subglacial sediments, marine sediment cores, relative sea-level (RSL) records, radar data, and ice cores. Of these, only subglacial bedrock and subglacial sediments can provide direct evidence for readvance. Marine archives are of limited utility because readvance commonly covers evidence of earlier retreat. Nevertheless, stratigraphic transitions documenting change in environment may provide support for direct evidence from subglacial records, as can the presence of transgressions in RSL records. With independent age control, past changes in ice structure and flow patterns revealed by radar can be used to infer ice volume changes commensurate with readvance. Since ice cores capture changes in surface mass balance, elevation, and changes in atmospheric and oceanic circulation that are known to drive grounding-line migration, they also have potential for identifying readvance. A multidisciplinary approach is likely to provide the strongest evidence for or against a smaller-than-present AIS in the Holocene.

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Interaction of ice sheets and climate during the past 800 000 years

Climate of the Past Discussions ◽

10.5194/cpd-10-2547-2014 ◽

2014 ◽

Vol 10 (3) ◽

pp. 2547-2594

Author(s):

L. B. Stap ◽

R. S. W. van de Wal ◽

B. de Boer ◽

R. Bintanja ◽

L. J. Lourens

Keyword(s):

Temperature Profile ◽

Sea Level ◽

Time Scales ◽

Ice Sheets ◽

Ice Sheet ◽

Ice Cores ◽

Atmospheric Temperature ◽

The Past ◽

Long Time ◽

And Sea Level

Abstract. During the Cenozoic, land ice and climate have interacted on many different time scales. On long time scales, the effect of land ice on global climate and sea level is mainly set by large ice sheets on North America, Eurasia, Greenland and Antarctica. The climatic forcing of these ice sheets is largely determined by the meridional temperature profile resulting from radiation and greenhouse gas (GHG) forcing. As response, the ice sheets cause an increase in albedo and surface elevation, which operates as a feedback in the climate system. To quantify the importance of these climate-land ice processes, a zonally-averaged energy balance climate model is coupled to five one-dimensional ice-sheet models, representing the major ice sheets. In this study, we focus on the transient simulation of the past 800 000 years, where a high-confidence CO2-record from ice cores samples is used as input in combination with Milankovitch radiation changes. We obtain simulations of atmospheric temperature, ice volume and sea level, that are in good agreement with recent proxy-data reconstructions. We examine long-term climate-ice sheet interactions by a comparison of simulations with uncoupled and coupled ice sheets. We show that these interactions amplify global temperature anomalies by up to a factor 2.6, and that they increase polar amplification by 94%. We demonstrate that, on these long time scales, the ice-albedo feedback has a larger and more global influence on the meridional atmospheric temperature profile than the surface-height temperature feedback. Furthermore, we assess the influence of CO2 and insolation, by performing runs with one or both of these variables held constant. We find that atmospheric temperature is controlled by a complex interaction of CO2 and insolation, and both variables serve as thresholds for Northern Hemispheric glaciation.

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The last deglaciation simulated with a coupled atmosphere/ocean/ice sheet/solid earth model

10.5194/egusphere-egu21-2278 ◽

2021 ◽

Author(s):

Uwe Mikolajewicz ◽

Olga Erokhina ◽

Marie-Luise Kapsch ◽

Clemens Schannwell ◽

Florian Ziemen

Keyword(s):

Deep Water ◽

Climate Changes ◽

Ice Sheets ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Earth Model ◽

Last Deglaciation ◽

The Holocene ◽

Simulated Climate ◽

The Last Deglaciation

It is challenging to model the last deglaciation, as it is characterized by abrupt millennial scale climate events, such as ice-sheet surges, that are superimposed on long-term climate changes, such as a global warming and the decay of a substantial part of the glacial ice sheets. Within PMIP, several groups have simulated the last deglaciation with CMIP-type models prescribing ice sheets from reconstructions. Whereas this type of simulations accounts for the effects of ice-sheet changes including meltwater release on climate, the prescribed ice sheet evolution is typically not consistent with the simulated climate evolution. Here we present a set of deglacial simulations that include fully interactive ice sheets that respond to changes in the climate. The setup also allows for feedbacks between ice sheets and climate and , hence, allows for a more realistic representation of the mechanisms of the last deglaciation, as the simulated climate and ice sheet changes are fully consistent..The model consists of the coarse resolution set-up of MPI-ESM coupled to the ice sheet model mPISM (Northern Hemisphere and Antarctica) and the solid earth model VILMA. The model includes interactive icebergs and an automated calculation of the land-sea mask and river routing directions. A set of synchronously coupled simulations were started from an asynchronously coupled spin-up at 26ky and integrated throughout the deglaciation into the Holocene. The only prescribed external forcing are atmospheric concentrations of greenhouse gases and earth orbital parameters. One goal of this ensemble was to find the optimal combination of model parameters for the simulation of the deglaciation.The model simulates the decay of the ice sheets, the rise of sea level, the flooding of shelf seas and the opening of passages. A large fraction of the ice sheet retreat is due to dynamical events (e.g. the final decay of the ice sheets on Barents Shelf or the Hudson Bay). Superimposed on the relatively slow glacial/interglacial transition are abrupt climate changes, triggered for example by recurrent ice sheet surges. These surges correspond to Heinrich Events tand result in a weakening of the AMOC. Three source regions for ice sheet surges occur during these simulations: from the Laurentide ice sheet through Hudson Strait, from the Laurentide ice sheet northward directly to the Arctic ocean, and from the Fennoscandian ice sheet into the Norwegian Sea. The characteristic climate response shows a large dependence on the surge location.The simulated changes in strength of the AMOC are except for millennial-scale reduction events only moderate. However, during glacial periods, brine release is the central process for deep water formation in both hemispheres, in contrast to the Holocene. dDuring the deglaciation the ventilation of the deep ocean is strongly reduced, leading to a strong increase of the simulated deep water ages. This effect lasts longest in the deep North Pacific and extends in some simulations into the Holocene.

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