Present and future mass balance of the ice sheets simulated with GCM

A high-resolution GCM ECHAM3 T106 was used to simulate the climates of the present and of the future under doubled CO2The ECHAM3 T106 was integrated for an equivalent time of 5 years (1) with the observed SST of the 1980s and (2) with the SST for the 2 × CO2climate generated from the ECHAM1 T21 coupled transient experiment. The main motivation for using the GCM to simulate the mass balance is the level of skill in simulating precipitation and accumulation recently achieved in the high-resolution GCM experiment. The ablation is computed, based on the GCM internal surface fluxes and the temperature/ablation relationship formulated on the Greenland field data. The two ice sheets show very different reactions towards doubling the CO2. As the decrease in accumulation and the increase in ablation in Greenland cause an annual mean specific mass balance of −225 mm (eq. −390 km3), the increase in accumulation and virtually non-melt conditions in Antarctica result in a mean annual specific mass balance of + 23 mm (eq. + 325 km3). The sum of the mass balance on both ice sheets is equivalent to the annual sea-level rise of 0.2 mm. This experiment shows that other mechanisms for sea-level change, such as the thermal expansion of the sea water and the melt of small mountain glaciers, will remain important in the coming century.

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Present and future mass balance of the ice sheets simulated with GCM

Annals of Glaciology ◽

10.3189/s0260305500013434 ◽

1996 ◽

Vol 23 ◽

pp. 187-193 ◽

Cited By ~ 2

Author(s):

Atsumu Ohmura ◽

Martin Wild ◽

Lennart Bengtsson

Keyword(s):

High Resolution ◽

Mass Balance ◽

Sea Level ◽

Sea Water ◽

Ice Sheets ◽

Internal Surface ◽

Surface Fluxes ◽

Specific Mass ◽

Mountain Glaciers ◽

Equivalent Time

A high-resolution GCM ECHAM3 T106 was used to simulate the climates of the present and of the future under doubled CO2 The ECHAM3 T106 was integrated for an equivalent time of 5 years (1) with the observed SST of the 1980s and (2) with the SST for the 2 × CO2 climate generated from the ECHAM1 T21 coupled transient experiment. The main motivation for using the GCM to simulate the mass balance is the level of skill in simulating precipitation and accumulation recently achieved in the high-resolution GCM experiment. The ablation is computed, based on the GCM internal surface fluxes and the temperature/ablation relationship formulated on the Greenland field data. The two ice sheets show very different reactions towards doubling the CO2. As the decrease in accumulation and the increase in ablation in Greenland cause an annual mean specific mass balance of −225 mm (eq. −390 km3), the increase in accumulation and virtually non-melt conditions in Antarctica result in a mean annual specific mass balance of + 23 mm (eq. + 325 km3). The sum of the mass balance on both ice sheets is equivalent to the annual sea-level rise of 0.2 mm. This experiment shows that other mechanisms for sea-level change, such as the thermal expansion of the sea water and the melt of small mountain glaciers, will remain important in the coming century.

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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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Trends and projections in ice sheet mass balance

10.5194/egusphere-egu2020-20660 ◽

2020 ◽

Author(s):

Andrew Shepherd ◽

Keyword(s):

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Dynamics ◽

Surface Mass ◽

Sea Levels ◽

Global Sea Level

<p>In recent decades, the Antarctic and Greenland Ice Sheets have been major contributors to global sea-level rise and are expected to be so in the future. Although increases in glacier flow and surface melting have been driven by oceanic and atmospheric warming, the degree and trajectory of today&#8217;s imbalance remain uncertain. Here we compare and combine 26 individual satellite records of changes in polar ice sheet volume, flow and gravitational potential to produce a reconciled estimate of their mass balance. <strong>Since the early 1990&#8217;s, ice losses from Antarctica and Greenland have caused global sea-levels to rise by 18.4 millimetres, on average, and there has been a sixfold increase in the volume of ice loss over time. Of this total, 41 % (7.6 millimetres) originates from Antarctica and 59 % (10.8 millimetres) is from Greenland. In this presentation, we compare our reconciled estimates of Antarctic and Greenland ice sheet mass change to IPCC projection of sea level rise to assess the model skill in predicting changes in ice dynamics and surface mass balance. &#160;</strong>Cumulative ice losses from both ice sheets have been close to the IPCC&#8217;s predicted rates for their high-end climate warming scenario, which forecast an additional 170 millimetres of global sea-level rise by 2100 when compared to their central estimate.</p>

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Ice sheet mass balance and sea level

Antarctic Science ◽

10.1017/s0954102009990137 ◽

2009 ◽

Vol 21 (5) ◽

pp. 413-426 ◽

Cited By ~ 58

Author(s):

I. Allison ◽

R.B. Alley ◽

H.A. Fricker ◽

R.H. Thomas ◽

R.C. Warner

Keyword(s):

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

Average Rate ◽

Ice Sheets ◽

Ice Sheet ◽

Measurement Technology ◽

Satellite Gravity ◽

Intergovernmental Panel ◽

Ice Sheet Mass Balance

AbstractDetermining the mass balance of the Greenland and Antarctic ice sheets (GIS and AIS) has long been a major challenge for polar science. But until recent advances in measurement technology, the uncertainty in ice sheet mass balance estimates was greater than any net contribution to sea level change. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (AR4) was able, for the first time, to conclude that, taken together, the GIS and AIS have probably been contributing to sea level rise over the period 1993–2003 at an average rate estimated at 0.4 mm yr-1. Since the cut-off date for work included in AR4, a number of further studies of the mass balance of GIS and AIS have been made using satellite altimetry, satellite gravity measurements and estimates of mass influx and discharge using a variety of techniques. Overall, these studies reinforce the conclusion that the ice sheets are contributing to present sea level rise, and suggest that the rate of loss from GIS has recently increased. The largest unknown in the projections of sea level rise over the next century is the potential for rapid dynamic collapse of ice sheets.

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Mass balance of glaciers other than the ice sheets

Journal of Glaciology ◽

10.3189/s0022143000002641 ◽

1998 ◽

Vol 44 (147) ◽

pp. 315-325 ◽

Cited By ~ 20

Author(s):

J. Graham Cogley ◽

W. P. Adams

Keyword(s):

Time Series ◽

Mass Balance ◽

Sea Level ◽

Spatial Interpolation ◽

Size Range ◽

Ice Sheets ◽

Spatial Coverage ◽

Complete Set ◽

The 1960S ◽

Global Data

AbstractSmall glaciers appear to have been at equilibrium or shrinking very slightly during 1961–90, according to analysis of an essentially complete set of published measurements. Simple calculations give an average annual mass balance of –195 ± 59 mm a−1 (water equivalent) but this is too low because of systematic errors. Neglect of internal accumulation is responsible for some tens of millimeters of underestimate. Uneven spatial coverage, with fewer measurements where mass balances are less negative, accounts for about 50 mm a−1 of underestimate. This figure derives from spatial interpolation based on global data on ice extent and on an analysis of correlations between balance time series. The correlogram shows exponential decay, the scale length being about 600 km. The largest bias is due to a newly detected dependence of mass balance on glacier size. Among the 231 measured glaciers, many are small and belong to a restricted size range in which balance is negative, but much of the small-glacier extent is accounted for by larger glaciers in a size range where balance is indistinguishable from zero. Correcting for this size bias increases the average balance to –35 ± 89 mm a−1. Inspection of time series for 1940–95 (251 glaciers) shows that mass balance was least negative during the 1960s, and has varied in broad agreement with Northern Hemisphere temperature anomalies; smaller small glaciers (A < 16 km2) appear to be more sensitive than larger small glaciers to changes in thermal forcing. The small-glacier contribution to sea-level rise implied by this assessment is only 0.06–0.32 mm a−1, consistent with glaciers in general making little or no contribution to sea-level change during 1961–90.

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Influence of temperature fluctuations on equilibrium ice sheet volume

The Cryosphere ◽

10.5194/tc-12-39-2018 ◽

2018 ◽

Vol 12 (1) ◽

pp. 39-47 ◽

Cited By ~ 7

Author(s):

Troels Bøgeholm Mikkelsen ◽

Aslak Grinsted ◽

Peter Ditlevsen

Keyword(s):

Mass Balance ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Temperature Fluctuations ◽

Surface Mass ◽

Ice Volume ◽

Recent Estimate ◽

Interannual Fluctuations

Abstract. Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing temperatures. The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an ice sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the ice sheet. We illustrate this in a simple ice sheet model and find that the equilibrium ice volume is approximately 1 m SLE (meters sea level equivalent) smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland Ice Sheet, we estimate the bias to be 30 Gt yr−1 (24–59 Gt yr−1, 95 % credibility) for a warming of 3 °C above preindustrial values, or 13 % (10–25, 95 % credibility) of the present-day rate of ice loss. Models of the Greenland Ice Sheet show a collapse threshold beyond which the ice sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10–0.18 °C, 95 % credibility) for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the mass balance of the ice sheets.

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Qualitative Modeling of Ice Sheet Accumulation for Identification of Mass Balance Variation

Advances in Web Technologies and Engineering - Dynamic Knowledge Representation in Scientific Domains ◽

10.4018/978-1-5225-5261-1.ch005 ◽

2018 ◽

pp. 99-118

Author(s):

Kirill Khvorostovsky ◽

Pavel Lunev ◽

Victoria Shterkhun

Keyword(s):

Climate Change ◽

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheets ◽

Physical Models ◽

Qualitative Model ◽

Qualitative Modeling ◽

Formation And Evolution ◽

Methods Of Measurement

Formation and evolution of ice sheets is one of the “hot” problems of modern geosciences, as it has direct implication on the issues of climate change and sea level rise. Different methods of measurement or computing the mass balance of modern ice sheets based on various physical models sometimes give conflicting results. To understand them, one should first reconcile the models they are based on. This, in turn, requires one to decipher the vision different researchers have on the generation and evolution of ice sheets. This vision is initially qualitative. Hence, a qualitative model is desired that would reconcile various, and sometimes conflicting, physical models. This chapter proposes this model.

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Mass balance of glaciers other than the ice sheets

Journal of Glaciology ◽

10.1017/s0022143000002641 ◽

1998 ◽

Vol 44 (147) ◽

pp. 315-325 ◽

Cited By ~ 76

Author(s):

J. Graham Cogley ◽

W. P. Adams

Keyword(s):

Time Series ◽

Mass Balance ◽

Sea Level ◽

Spatial Interpolation ◽

Size Range ◽

Ice Sheets ◽

Spatial Coverage ◽

Complete Set ◽

The 1960S ◽

Global Data

AbstractSmall glaciers appear to have been at equilibrium or shrinking very slightly during 1961–90, according to analysis of an essentially complete set of published measurements. Simple calculations give an average annual mass balance of –195 ± 59 mm a−1(water equivalent) but this is too low because of systematic errors. Neglect of internal accumulation is responsible for some tens of millimeters of underestimate. Uneven spatial coverage, with fewer measurements where mass balances are less negative, accounts for about 50 mm a−1of underestimate. This figure derives from spatial interpolation based on global data on ice extent and on an analysis of correlations between balance time series. The correlogram shows exponential decay, the scale length being about 600 km. The largest bias is due to a newly detected dependence of mass balance on glacier size. Among the 231 measured glaciers, many are small and belong to a restricted size range in which balance is negative, but much of the small-glacier extent is accounted for by larger glaciers in a size range where balance is indistinguishable from zero. Correcting for this size bias increases the average balance to –35 ± 89 mm a−1. Inspection of time series for 1940–95 (251 glaciers) shows that mass balance was least negative during the 1960s, and has varied in broad agreement with Northern Hemisphere temperature anomalies; smaller small glaciers (A< 16 km2) appear to be more sensitive than larger small glaciers to changes in thermal forcing. The small-glacier contribution to sea-level rise implied by this assessment is only 0.06–0.32 mm a−1, consistent with glaciers in general making little or no contribution to sea-level change during 1961–90.

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Change in mass balance of polar ice sheets and sea level from high-resolution GCM simulations of greenhouse warming

Annals of Glaciology ◽

10.3189/172756400781820741 ◽

2000 ◽

Vol 30 ◽

pp. 197-203 ◽

Cited By ~ 26

Author(s):

Martin Wild ◽

Atsumu Ohmura

Keyword(s):

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

General Circulation ◽

Ice Sheets ◽

General Circulation Models ◽

Dominant Factor ◽

Greenhouse Warming ◽

Sea Level Changes ◽

And Sea Level

AbstractFor projecting future sea level, the mass-balance changes on Greenland and Antarctica are considered to be crucial. Promising tools for such estimates are general circulation models (GCM). Until recently, a major impediment was their coarse grid resolution (3°-6°) causing substantial uncertainties in the mass-balance calculations of the poorly resolved ice sheets. The present study is based on a new climate-change experiment of the highest resolution currently feasible (1.1 °) performed with the ECHAM4 T106 GCM, thereby increasing confidence in the projected mass-balance and sea-level changes. This new experiment, with doubled CO2 concentration, suggests that the mass gain in Antarctica due to increased accumulation exceeds the melt-induced mass loss in Greenland by a factor of three. The resulting mass-balance change on both ice sheets is equivalent to a net sea-level decrease of 0.6 mm a"1 under doubled CO2 conditions. This may compensate for a significant portion of the melt-induced sea-level rise from the smaller glaciers and ice caps, thus leaving thermal expansion as the dominant factor for sea-level rise over the next decades. This compensating effect, however, no longer applies should atmospheric CO2 concentration reach levels well above "doubled the present value". On the contrary, under these conditions, the greenhouse warming would become large enough to induce substantial melting also on the Antarctic ice sheet, thereby significantly accelerating global sea-level rise.

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