How Bølling warming and ice saddles fed MWP1a
North American ice-sheet ensembles show saddle collapse and Bølling warming can supply several meters of Meltwater Pulse 1a in 340 years.
Source
Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise
Study at a glance
- Design
- Computational / modelling — Glimmer-CISM North American deglaciation ensembles forced by FAMOUS and CCSM3 climates
- N
- N=603 · 603 deglaciation experiments; 340-year Meltwater Pulse 1a windows
- Population
- Cordilleran–Laurentide ice-sheet model ensemble
- Outcome
- Ice-saddle collapse plus Bølling warming can supply several meters of Meltwater Pulse 1a sea-level rise in 340 years
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Inspect source passages
How Bølling warming and ice saddles fed MWP1a
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Each forcing used 201 experiments, 603 simulations in total.
For each climate forcing (Fabs, Cabs, and Cano), we ran a perturbed physics parameter ensemble of 201 experiments, 603 simulations in total.
Why can’t FAMOUS assess Bølling melt?
The F‐21k (Fabs) forcing does not include a Bølling warming signal and so cannot be used to assess the climate event's influence on North American ice sheet evolution.
What they did
Authors ran 603 Glimmer-CISM deglaciation experiments forced by FAMOUS and CCSM3 climates, selected geologically plausible members, and measured 340-year melt pulses from Cordilleran–Laurentide separation versus Bølling warming.
What they found
Saddle collapse alone yields 5.7–11.0 m of GMSL in 340 years, but too late unless Bølling warming helps. When Bølling triggers separation, North America contributes about 5–6 m; if already separated, only about 3–4 m.
The limits
What it doesn't show
Shallow-ice physics omits marine instability and ice streams; FAMOUS has no Bølling; CCSM3 ice-mask steps required discarding some melt spikes; Antarctic sources are not modeled here.
Key terms
- Meltwater Pulse 1a
- Rapid ~14–18 m sea-level rise in <340 years around 14.6 ka.
- Saddle collapse
- Accelerated melt when the Cordilleran and Laurentide ice sheets separate.
- Bølling warming
- Abrupt Northern Hemisphere warming near 14.6 ka.
- Glimmer-CISM
- 3-D thermodynamic ice-sheet model used for the ensembles.
- Anomaly forcing
- GCM climate applied as anomalies to reduce present-day bias (Cano).
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MWP1a coral-record size cited:
Common questions
How big is MWP1a in the coral records cited?
14–18 m of GMSL in less than 340 years at 14.6 ka.
Saddle-collapse pulse size in Fabs?
5.7–11.0 m GMSL in 340 years.
Bølling-only contribution if ice sheets already split?
About 3–4 m in 340 years.
How many simulations were run?
603 (201 per climate forcing).
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