Limits...
A geological perspective on potential future sea-level rise.

Rohling EJ, Haigh ID, Foster GL, Roberts AP, Grant KM - Sci Rep (2013)

Bottom Line: This context supports SLR of up to 0.9 (1.8) m by 2100 and 2.7 (5.0) m by 2200, relative to 2000, at 68% (95%) probability.Hence, modern change is rapid by past interglacial standards but within the range of 'normal' processes.The upper 95% limit offers a useful low probability/high risk value.

View Article: PubMed Central - PubMed

Affiliation: 1] Research School of Earth Sciences, The Australian National University, Canberra 0200 Australia [2] Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK.

ABSTRACT
During ice-age cycles, continental ice volume kept pace with slow, multi-millennial scale, changes in climate forcing. Today, rapid greenhouse gas (GHG) increases have outpaced ice-volume responses, likely committing us to > 9 m of long-term sea-level rise (SLR). We portray a context of naturally precedented SLR from geological evidence, for comparison with historical observations and future projections. This context supports SLR of up to 0.9 (1.8) m by 2100 and 2.7 (5.0) m by 2200, relative to 2000, at 68% (95%) probability. Historical SLR observations and glaciological assessments track the upper 68% limit. Hence, modern change is rapid by past interglacial standards but within the range of 'normal' processes. The upper 95% limit offers a useful low probability/high risk value. Exceedance would require conditions without natural interglacial precedents, such as catastrophic ice-sheet collapse, or activation of major East Antarctic mass loss at sustained CO2 levels above 1000 ppmv.

No MeSH data available.


Related in: MedlinePlus

Histogram of tinf, the relative age of the inflection from concave to convex in our 2000 sigmoidal (logistic) SLR rate reconstructions.
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f4: Histogram of tinf, the relative age of the inflection from concave to convex in our 2000 sigmoidal (logistic) SLR rate reconstructions.

Mentions: The processes that govern mass-loss from ice sheets build up gradually because of dynamical spin-up or due to slow increases in early melting until ice-sheet height-temperature feedbacks lead to rapid acceleration9545859. Hence, our assessment allows rates of SLR to gradually build, and then accelerate, before settling at the maximum achievable rate for the mechanisms involved (α in our analysis below, in m y−1). We approximate this using a logistic function of the form: Here γ is the timescale over which the rate increases from zero to its peak value (in y). β is discussed below. The dimensionless scaling constant C is empirically set so that γ equals the period over which d2ΔS/dt2 exceeds 1% of its maximum value. C is independent of α, β, and γ; it depends merely on the cutoff criterion used for d2ΔS/dt2. Our consistently applied criterion implies that C = 12 in all iterations. The timing of the central inflection in dΔS/dt, the switch-over from accelerating to decelerating rates of SLR (with the constraint that at AD2000, the SLR rate is 3 ± 1 mm y−1, see below), is tinf = γ ln(β)/C. A histogram for all 2000 iterations (Figure 4) suggests that tinf falls within a window of ~300 years. For comparison, modeled developments from zero to maximum SLR rates from Greenland, over a wide range of climate forcing scenarios, suggest inflection-point timings within a 200-year window (2100–2300) (analysis based on Figure 3b of ref. 59), which is qualitatively similar to our inference.


A geological perspective on potential future sea-level rise.

Rohling EJ, Haigh ID, Foster GL, Roberts AP, Grant KM - Sci Rep (2013)

Histogram of tinf, the relative age of the inflection from concave to convex in our 2000 sigmoidal (logistic) SLR rate reconstructions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3860070&req=5

f4: Histogram of tinf, the relative age of the inflection from concave to convex in our 2000 sigmoidal (logistic) SLR rate reconstructions.
Mentions: The processes that govern mass-loss from ice sheets build up gradually because of dynamical spin-up or due to slow increases in early melting until ice-sheet height-temperature feedbacks lead to rapid acceleration9545859. Hence, our assessment allows rates of SLR to gradually build, and then accelerate, before settling at the maximum achievable rate for the mechanisms involved (α in our analysis below, in m y−1). We approximate this using a logistic function of the form: Here γ is the timescale over which the rate increases from zero to its peak value (in y). β is discussed below. The dimensionless scaling constant C is empirically set so that γ equals the period over which d2ΔS/dt2 exceeds 1% of its maximum value. C is independent of α, β, and γ; it depends merely on the cutoff criterion used for d2ΔS/dt2. Our consistently applied criterion implies that C = 12 in all iterations. The timing of the central inflection in dΔS/dt, the switch-over from accelerating to decelerating rates of SLR (with the constraint that at AD2000, the SLR rate is 3 ± 1 mm y−1, see below), is tinf = γ ln(β)/C. A histogram for all 2000 iterations (Figure 4) suggests that tinf falls within a window of ~300 years. For comparison, modeled developments from zero to maximum SLR rates from Greenland, over a wide range of climate forcing scenarios, suggest inflection-point timings within a 200-year window (2100–2300) (analysis based on Figure 3b of ref. 59), which is qualitatively similar to our inference.

Bottom Line: This context supports SLR of up to 0.9 (1.8) m by 2100 and 2.7 (5.0) m by 2200, relative to 2000, at 68% (95%) probability.Hence, modern change is rapid by past interglacial standards but within the range of 'normal' processes.The upper 95% limit offers a useful low probability/high risk value.

View Article: PubMed Central - PubMed

Affiliation: 1] Research School of Earth Sciences, The Australian National University, Canberra 0200 Australia [2] Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK.

ABSTRACT
During ice-age cycles, continental ice volume kept pace with slow, multi-millennial scale, changes in climate forcing. Today, rapid greenhouse gas (GHG) increases have outpaced ice-volume responses, likely committing us to > 9 m of long-term sea-level rise (SLR). We portray a context of naturally precedented SLR from geological evidence, for comparison with historical observations and future projections. This context supports SLR of up to 0.9 (1.8) m by 2100 and 2.7 (5.0) m by 2200, relative to 2000, at 68% (95%) probability. Historical SLR observations and glaciological assessments track the upper 68% limit. Hence, modern change is rapid by past interglacial standards but within the range of 'normal' processes. The upper 95% limit offers a useful low probability/high risk value. Exceedance would require conditions without natural interglacial precedents, such as catastrophic ice-sheet collapse, or activation of major East Antarctic mass loss at sustained CO2 levels above 1000 ppmv.

No MeSH data available.


Related in: MedlinePlus