Response of the Wilkes Subglacial Basin Ice Sheet to Southern Ocean Warming During Late Pleistocene Interglacials

Abstract The response of the East Antarctic Ice Sheet to past intervals of oceanic and atmospheric warming is still not well constrained but critical for understanding both past and future sea-level change. Furthermore, the ice sheet in the Wilkes Subglacial Basin, which is characterized by a reverse-sloping bed, appears to have undergone thinning and ice discharge events during recent decades. By combining new glaciological evidence on ice sheet elevation from the TALDICE ice core with offshore sedimentological records and ice sheet modelling experiments, we reconstruct the ice dynamics in the Wilkes Subglacial Basin over the past 350,000 years. Our results indicate that the Wilkes Subglacial Basin experienced an extensive retreat 330,000 years ago and a more limited retreat 125,000 years ago. These changes coincided with warmer Southern Ocean temperatures and elevated global mean sea level during those interglacial periods, confirming the sensitivity of the Wilkes Subglacial Basin ice sheet to ocean warming and its potential role in sea-level change.

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The response of large ice sheets to climatic change

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1992.0143 ◽

1992 ◽

Vol 338 (1285) ◽

pp. 235-242 ◽

Cited By ~ 23

Keyword(s):

Mass Balance ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Sea Level Change ◽

Mixing Ratio ◽

Ice Dynamics ◽

Environmental Models ◽

Level Change ◽

The Antarctic

The prediction of short-term (100 year) changes in the mass balance of ice sheets and longer-term (1000 years) variations in their ice volumes is important for a range of climatic and environmental models. The Antarctic ice sheet contains between 24 M km 3 and 29 M km 3 of ice, equivalent to a eustatic sea level change of between 60m and 72m. The annual surface accumulation is estimated to be of the order of 2200 Gtonnes, equivalent to a sea level change of 6 mm a -1 . Analysis of the present-day accumulation regime of Antarctica indicates that about 25% ( ca. 500 Gt a -1 ) of snowfall occurs in the Antarctic Peninsula region with an area of only 6.8% of the continent. To date most models have focused upon solving predictive algorithms for the climate-sensitivity of the ice sheet, and assume: (i) surface mass balance is equivalent to accumulation (i.e. no melting, evaporation or deflation); (ii) percentage change in accumulation is proportional to change in saturation mixing ratio above the surface inversion layer; and (iii) there is a linear relation between mean annual surface air tem perature and saturation mixing ratio. For the A ntarctic Peninsula with mountainous terrain containing ice caps, outlet glaciers, valley glaciers and ice shelves, where there can be significant ablation at low levels and distinct climatic regimes, models of the climate response must be more complex. In addition, owing to the high accumulation and flow rates, even short- to medium -term predictions must take account of ice dynamics. Relationships are derived for the mass balance sensitivity and, using a model developed by Hindmarsh, the transient effects of ice dynamics are estimated. It is suggested that for a 2°C rise in mean annual surface tem perature over 40 years, ablation in the A ntarctic Peninsula region would contribute at least 1.0 mm to sea level rise, offsetting the fall of 0.5 mm contributed by increased accum ulation.

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Global Mean Sea Level Change: Correction

Science ◽

10.1126/science.275.5303.1049i ◽

1997 ◽

Vol 275 (5303) ◽

pp. 1049i-1053 ◽

Cited By ~ 12

Author(s):

R. S. Nerem

Keyword(s):

Sea Level ◽

Sea Level Change ◽

Mean Sea Level ◽

Level Change ◽

Global Mean Sea Level ◽

Global Mean

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Global sea-level and ocean-mass budgets using advanced data products and uncertainty characterisation

10.5194/egusphere-egu21-10174 ◽

2021 ◽

Author(s):

Martin Horwath ◽

Anny Cazenave ◽

Keyword(s):

Time Series ◽

Sea Level ◽

Satellite Altimetry ◽

Sea Level Change ◽

Mass Change ◽

Level Change ◽

Ocean Mass ◽

Global Mean Sea Level ◽

Global Sea Level ◽

Global Mean

Studies of the global sea-level budget (SLB) and ocean-mass budget (OMB) are essential to assess the reliability of our knowledge of sea-level change and its contributors. The SLB is considered closed if the observed sea-level change agrees with the sum of independently assessed steric and mass contributions. The OMB is considered closed if the observed ocean-mass change is compatible with the sum of assessed mass contributions.&#160;Here we present results from the Sea-Level Budget Closure (SLBC_cci) project conducted in the framework of ESA&#8217;s Climate Change Initiative (CCI). We used data products from CCI projects as well as newly-developed products based on CCI products and on additional data sources. Our focus on products developed in the same framework allowed us to exercise a consistent uncertainty characterisation and its propagation to the budget closure analyses, where the SLB and the OMB are assessed simultaneously.&#160;We present time series of global mean sea-level changes from satellite altimetry; new time series of the global mean steric component generated from Argo drifter data with incorporation of sea surface temperature data; time series of ocean-mass change derived from GRACE satellite gravimetry; time series of global glacier mass change from a global glacier model; time series of mass changes of the Greenland Ice Sheet and the Antarctic Ice Sheet both from satellite radar altimetry and from GRACE; as well as time series of land water storage change from the WaterGAP global hydrological model. Our budget analyses address the periods 1993&#8211;2016 (covered by the satellite altimetry records) and 2003&#8211;2016 (covered by GRACE and the Argo drifter system). In terms of the mean rates of change (linear trends), the SLB is closed within uncertainties for both periods, and the OMB, assessable for 2003&#8211;2016 only, is also closed within uncertainties. Uncertainties (1-sigma) arising from the combined uncertainties of the elements of the different budgets considered are between 0.26 mm/yr and 0.40 mm/yr, that is, on the order of 10% of the magnitude of global mean sea-level rise, which is 3.05 &#177; 0.24 mm/yr and 3.65 &#177; 0.26 mm/yr for 1993-2016 and 2003-2016, respectively. We also assessed the budgets on a monthly time series basis. The statistics of monthly misclosure agrees with the combined uncertainties of the budget elements, which amount to typically 2-3 mm for the 2003&#8211;2016 period. We discuss possible origins of the residual misclosure.

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Variations in global mean sea level associated with the 1997-1998 ENSO event: Implications for measuring long term sea level change

Geophysical Research Letters ◽

10.1029/1999gl002311 ◽

1999 ◽

Vol 26 (19) ◽

pp. 3005-3008 ◽

Cited By ~ 91

Author(s):

R. S. Nerem ◽

D. P. Chambers ◽

E. W. Leuliette ◽

G. T. Mitchum ◽

B. S. Giese

Keyword(s):

Sea Level ◽

Sea Level Change ◽

Enso Event ◽

Mean Sea Level ◽

Level Change ◽

Global Mean Sea Level ◽

Global Mean

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Sea State Bias Variability in Satellite Altimetry Data

Remote Sensing ◽

10.3390/rs11101176 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1176

Author(s):

Yongcun Cheng ◽

Qing Xu ◽

Le Gao ◽

Xiaofeng Li ◽

Bin Zou ◽

...

Keyword(s):

Sea Level ◽

Sea Level Change ◽

Sea State ◽

Mean Sea Level ◽

Level Change ◽

Sea State Bias ◽

Regional Sea Level ◽

Sea Level Trend ◽

Global Mean Sea Level ◽

Global Mean

Sea State Bias (SSB) contributes to global mean sea level variability and it needs cm-level range adjustment due to the instrumental drift over time. To investigate its variations and correct the global and regional sea level trend precisely, we calculate the temporal and spatial variability of the SSB correction in TOPEX, Jason-1, Jason-2 and Jason-3 missions, separately, as well as in the combined missions over the period 1993–2017. The long-term trend in global mean operational 2D non-parametric SSB correction is about −0.03 ± 0.03 mm/yr, which accounts for 1% of current global mean sea level change rate during 1993–2016. This correction contributes to sea level change rates of −1.27 ± 0.21 mm/yr and −0.26 ± 0.13 mm/yr in TOPEX-A and Jason-2 missions, respectively. The global mean SSB varies up to 7–10 mm during the very strong ENSO events in 1997–1998 and 2015–2016. Furthermore, the TOPEX SSB trend, which is consistent with recently reported sea level trend drift during 1993–1998, may leak into the determined global sea level trend in the period. Moreover, the Jason-1/2 zonal SSB variability is highly correlated with the significant wave height (SWH). On zonal average, SSB correction causes about 1% uncertainty in mean sea level trend. At high SWH regions, the uncertainties grow to 2–4% near the 50°N and 60°S bands. This should be considered in the study of regional sea level variability.

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Evaluating Model Simulations of Twentieth-Century Sea Level Rise. Part I: Global Mean Sea Level Change

Journal of Climate ◽

10.1175/jcli-d-17-0110.1 ◽

2017 ◽

Vol 30 (21) ◽

pp. 8539-8563 ◽

Cited By ~ 23

Author(s):

Aimée B. A. Slangen ◽

Benoit Meyssignac ◽

Cecile Agosta ◽

Nicolas Champollion ◽

John A. Church ◽

...

Keyword(s):

Twentieth Century ◽

Thermal Expansion ◽

Sea Level Rise ◽

Sea Level ◽

Sea Level Change ◽

Mean Sea Level ◽

Level Change ◽

The World ◽

Global Mean Sea Level ◽

Global Mean

Sea level change is one of the major consequences of climate change and is projected to affect coastal communities around the world. Here, global mean sea level (GMSL) change estimated by 12 climate models from phase 5 of the World Climate Research Programme’s Climate Model Intercomparison Project (CMIP5) is compared to observational estimates for the period 1900–2015. Observed and simulated individual contributions to GMSL change (thermal expansion, glacier mass change, ice sheet mass change, landwater storage change) are analyzed and compared to observed GMSL change over the period 1900–2007 using tide gauge reconstructions, and over the period 1993–2015 using satellite altimetry estimates. The model-simulated contributions explain 50% ± 30% (uncertainties 1.65 σ unless indicated otherwise) of the mean observed change from 1901–20 to 1988–2007. Based on attributable biases between observations and models, a number of corrections are proposed, which result in an improved explanation of 75% ± 38% of the observed change. For the satellite era (from 1993–97 to 2011–15) an improved budget closure of 102% ± 33% is found (105% ± 35% when including the proposed bias corrections). Simulated decadal trends increase over the twentieth century, both in the thermal expansion and the combined mass contributions (glaciers, ice sheets, and landwater storage). The mass components explain the majority of sea level rise over the twentieth century, but the thermal expansion has increasingly contributed to sea level rise, starting from 1910 onward and in 2015 accounting for 46% of the total simulated sea level change.

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Seasonal global mean sea level change from satellite altimeter, GRACE, and geophysical models

Journal of Geodesy ◽

10.1007/s00190-005-0005-9 ◽

2005 ◽

Vol 79 (9) ◽

pp. 532-539 ◽

Cited By ~ 48

Author(s):

J. L. Chen ◽

C. R. Wilson ◽

B. D. Tapley ◽

J. S. Famiglietti ◽

Matt Rodell

Keyword(s):

Sea Level ◽

Sea Level Change ◽

Satellite Altimeter ◽

Mean Sea Level ◽

Level Change ◽

Global Mean Sea Level ◽

Global Mean

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Effects of Sea-Level Rise and Subsidence on Deltas

Deltas and Humans ◽

10.1093/oso/9780199764174.003.0010 ◽

2016 ◽

Author(s):

Thomas S. Bianchi

Keyword(s):

Thermal Expansion ◽

Global Warming ◽

Sea Level Rise ◽

Sea Level ◽

Sea Level Change ◽

Mean Sea Level ◽

Level Change ◽

Global Mean Sea Level ◽

Global Sea Level ◽

Global Mean

As I briefly mentioned in Chapter 3, the global mean sea level, as deduced from the accumulation of paleo-sea level, tide gauge, and satellite-altimeter data, rose by 0.19 m (range, 0.17–0.21 m) between 1901 and 2010 (see Figure 3.3). Global mean sea level represents the longer-term global changes in sea level, without the short-term variability, and is also commonly called eustatic sea-level change. On an annual basis, global mean sea-level change translates to around 1.5 to 2 mm. During the last century, global sea level rose by 10 to 25 cm. Projections of sea-level rise for the period from 2000 to 2081 indicate that global mean sea-level rise will likely be as high as 0.52 to 0.98 m, or 8 to 16 mm/ yr, depending on the greenhouse gas emission scenarios used in the models. Mean sea-level rise is primarily controlled by ocean thermal expansion. But there is also transfer of water from land to ocean via melting of land ice, primarily in Greenland and Antarctica. Model predictions indicate that thermal expansion will increase with global warming because the contribution from glaciers will decrease as their volume is lost over time. (Take a look at Figure 5.1 if you have doubts about glaciers melting.) And remember our discussion in Chapter 2 about the role of the oceans in absorbing carbon dioxide (CO2) and the resultant ocean acidification in recent years. The global ocean also absorbs about 90% of all the net energy increase from global warming as well, which is why the ocean temperature is increasing, which in turn results in thermal expansion and sea-level rise. To make things even more complicated, the expansion of water will vary with latitude because expansion of seawater is greater with increasing temperature. In any event, sea level is expected to rise by 1 to 3 m per degree of warming over the next few millennia.

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The land-ice contribution to 21st-century dynamic sea level rise

Ocean Science ◽

10.5194/os-10-485-2014 ◽

2014 ◽

Vol 10 (3) ◽

pp. 485-500 ◽

Cited By ~ 8

Author(s):

T. Howard ◽

J. Ridley ◽

A. K. Pardaens ◽

R. T. W. L. Hurkmans ◽

A. J. Payne ◽

...

Keyword(s):

Sea Level ◽

21St Century ◽

Sea Level Change ◽

Sea Level Changes ◽

Mean Sea Level ◽

Ice Melt ◽

Level Change ◽

Global Mean Sea Level ◽

Global Mean ◽

Dynamic Sea Level

Abstract. Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere–ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

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Projecting Global Mean Sea-Level Change Using CMIP6 Models

10.5194/egusphere-egu21-1965 ◽

2021 ◽

Author(s):

Tim Hermans ◽

Jonathan Gregory ◽

Matthew Palmer ◽

Mark Ringer ◽

Caroline Katsman ◽

...

Keyword(s):

Sea Level ◽

Climate Models ◽

Sea Level Change ◽

Global Climate Models ◽

Mean Sea Level ◽

Level Change ◽

Global Mean Sea Level ◽

The Impact ◽

Global Mean ◽

Emissions Scenario

The effective climate sensitivity (EffCS) of models in the Coupled Model Intercomparison Project 6 (CMIP6) has increased relative to CMIP5. Consequently, using CMIP6 models tends to lead to larger projections of global mean surface air temperature (GSAT) increase for a given emissions scenario. The effect of increased EffCS on projections of global mean sea-level (GMSL) change however, has so far only been studied using a reduced complexity model. Here, we explore the implications of increased EffCS in CMIP6 models for GMSL change projections in 2100 for three emissions scenarios: SSP5-8.5, SSP2-4.5 and SSP1-2.6.Whereas CMIP6 projections of GSAT change are substantially higher than in CMIP5, projections of global mean thermal expansion (GTE) are only slightly higher. We use these projections as input to construct projections of GMSL change, using the Monte Carlo approach of IPCC AR5. Isolating the impact of the CMIP6 simulations using consistent methods is an important step to ensure traceability to past IPCC projections of global and regional sea-level change. The resulting 95th percentile of projected GMSL change at 2100 is only 3-7 cm higher for CMIP6 than for CMIP5, depending on the emissions scenario. Projected rates of GMSL rise around 2100 increase more strongly from CMIP5 to CMIP6, though, implying more pronounced differences beyond 2100 and greater committed sea-level rise. GMSL change in 2100 is accurately predicted by time-integrated temperature change and therefore mitigation requires early reduction of emissions.We also find that the 95th percentile projections based on individual CMIP6 models can differ as much as 51 cm and that the 5-95% range of projected GMSL change for individual CMIP6 models can be substantially outside of the 5-95% range of the CMIP6 multi-model ensemble. Thus, through subsetting the CMIP6 ensemble using EffCS, a choice can be made between characterizing the central part of the probability distribution and more comprehensively sampling the high end of the GMSL projection space, which is relevant to risk-averse stakeholders. Our results show this may substantially alter ensemble projections, underlining the need to constrain EffCS in global climate models in order to reduce uncertainty in sea-level projections.

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