I have provided copious extracts (& the four attached images) from the linked reference that studies four deep East Antarctic ice cores, with time resolutions as fine as 200-years, specifically to study the sensitivity of the WAIS to collapse during the Eemian peak (circa 128 ka ago). While the study provides valuable (& useful) scientific information, the authors seem to lean over backwards to demonstrate that under peak Eemian conditions (with 300ppm CO₂) that the entire WAIS did not entirely (but very likely partially) collapsed within the 200-year period resolution offered by their ice cores. They offer an alternate hypothesis (to rapid WAIS collapse), which matches their observations, and that likely requires invocations of the bipolar seesaw mechanism (driven by ice mass loss from the GIS) to warm the Southern Ocean, resulting in relatively rapid sea ice coverage loss around Antarctica. However, I emphasize that none of their findings run counter to the findings of either Hansen et. al. (2016) or DeConto & Pollard (2016); nor do they preclude DeConto's EGU finding that the WAIS could largely collapse abruptly if/when the modern GMST anom reaches/exceeds 2.7C:
Max D. Holloway, Louise C. Sime, Joy S. Singarayer, Julia C. Tindall, Pete Bunch & Paul J. Valdes (August 16, 2016), "Antarctic last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse", Nature Communications, Volume: 7, Article number: 12293, doi:10.1038/ncomms12293
http://www.nature.com/ncomms/2016/160816/ncomms12293/full/ncomms12293.html?WT.ec_id=NCOMMS-20160817&spMailingID=52079988&spUserID=ODkwMTM2NjQyNgS2&spJobID=983091385&spReportId=OTgzMDkxMzg1S0Abstract: "Several studies have suggested that sea-level rise during the last interglacial implies retreat of the West Antarctic Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak Antarctic temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of Antarctic sea ice extent to climate warming."
Extract: "During the last interglacial (LIG; 130,000–115,000 years ago) global climate was warmer than today and global mean sea level was 6-9 m higher. This LIG sea-level high stand was mainly driven by ice-sheet loss. Recent ice core results indicate that the Greenland ice sheet likely provided a modest 2 m contribution towards the global sea-level rise5, with estimates ranging from +1.4 m to +4.3 m. This implies that ice loss from the West Antarctic Ice Sheet (WAIS) must have contributed to the LIG sea-level maxima: loss of the entire WAIS would contribute 3–4 m of global sea-level rise. Coral records from Western Australia indicate that the sea level rose late in the interglacial, ~118,000 years ago (118 kyr ago). However, Seychelles coral has been interpreted as indication of a +5 m global sea level at 128 ka. These differing interpretations prevent constraint on the timing of WAIS loss, thus reducing the potential to use the LIG to inform the debate on the likelihood of future WAIS loss. We therefore turn to the ice core records to push forward the WAIS loss debate.
The recent ice core drilled at WAIS Divide does not extend back through the LIG; ice that may have been present during the LIG has since been lost through basal melt. However, ice cores extending back throughout the LIG, at a resolution of <200 years per metre of ice, are available from four locations on the East Antarctic Ice Sheet …
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We have explored only complete WAIS loss, rather than WAIS reduction, scenarios here. Our results thus do not preclude some loss of the WAIS by 128 ka, or that the WAIS may have been lost later in the LIG, possibly preconditioned by the early retreat of Southern Hemisphere sea ice. Indeed, loss of the WAIS between 128 and 125 kyr ago and a meltwater driven build-up of Southern Hemisphere sea ice may provide an explanation for the late LIG δ18O drop observed in ice core records; the δ18O trend throughout the early LIG, with a significant peak and subsequent drop, is distinct from the isotope record of the present interglacial (Fig. 1). Our results indicate that the LIG isotope trend may be consistent with a WAIS collapse and sea ice build-up in the following few thousand years of the isotope maximum.
The difference between an isotope record from Mt. Moulton and East Antarctic ice core records may also be consistent with a slow loss of the WAIS, which could have been mostly melted after another 2,000 years, by ~126 kyr ago. Lower isotope anomalies in the Mt. Moulton record relative to isotope records from East Antarctica suggest a local cooling anomaly, which is consistent with climate model simulations of WAIS collapse driven by pre-industrial boundary conditions27. The low isotope values in the Mt. Moulton record, relative to the other ice core sites, persists throughout the LIG, but the difference is greatest after ~126 kyr ago, perhaps coinciding with maximum retreat of the WAIS. Considering the reasonable agreement between the observed peak-to-trough δ18O anomalies and those calculated between our sea ice retreat and the WAIS loss experiments (Supplementary Fig. 5), we suggest that a large sea ice retreat best explains the early isotope maximum and a subsequent retreat of the WAIS, and sea ice build-up could provide an explanation for the observed pattern of isotope anomalies following the LIG maximum.
The bipolar seesaw mechanism proposes that a slowdown in northwards ocean heat transport, particularly in the Atlantic, tends to warm the Southern Ocean. This mechanism is consistent with a recent bipolar re-interpretation of the early LIG, alongside a recent synthesis of sea surface temperature reconstructions between 40 and 60° S (ref. 3). These all support Southern Ocean warming at 128 ka, providing a partial explanation for why Southern Hemisphere sea ice retreated at 128 ka. In future work, we will investigate whether the bipolar seesaw can provide the mechanism to cause a major Southern Hemisphere sea ice retreat and thus reconcile the 128 ka δ18O maximum. Further simulations, including WAIS loss and North Atlantic meltwater input, could provide insight into the non-linear interactions between the bipolar seesaw, the WAIS and Southern Hemisphere sea ice.
Finally, we note the similarity between the wintertime sea ice reduction of up to 58% forecast for the end of the 21st century and our 58–72% decrease suggested for 128 ka. This implies that the 128 ka sea ice retreat may prove a crucial model–data target for the sea ice modelling community. Currently, the most recent Coupled Model Intercomparison Project Phase 5 multi-model simulations do not simulate a reduction in September sea ice area >13% between the LIG and the present interglacial (Supplementary Discussion; Supplementary Table 2). Considering the disagreement between modelled and observed Antarctic sea ice during the satellite era, a number of studies have called for improvements in the modelling of climate and climate change in the Antarctic region. Whether this recent discrepancy is a function of natural variability or represents a failing of current climate models is still a matter of debate. If the currently observed increase in Antarctic sea ice is robust, a major reduction at 128 ka could indicate a tipping point in the sea ice system. There is clearly a need for more (and more robust) data for Antarctica and the surrounding sea ice edge during the LIG. If it is possible to correctly simulate the 128 ka sea ice reduction, it would improve the low confidence associated with future predictions of Southern Hemisphere sea ice change and, subsequently, improve projections of Antarctic temperature, precipitation and mass balance."
See also:
http://www.independent.co.uk/news/science/west-antarctic-ice-sheet-sea-level-rise-global-warming-climate-change-british-antarctic-survey-a7195481.htmlExtract: "She said their results suggested the ice sheet had not melted within about 50 to 200 years – a ‘sudden’ change in these terms. “It probably took longer than that,” she said.
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The broader lesson from 128,000 years ago is somewhat concerning. The temperature was higher than today even though the level of carbon dioxide in the atmosphere reached just 300 parts per million (ppm), compared to 400ppm today.
“The climate [today] hasn’t had time to respond fully to the CO2 we’ve put into the atmosphere,” Dr Sime said.
“We are now heading for a time that will be almost certainly warmer than the last interglacial. It’s just we haven’t got there yet.
“It’s really interesting to look at the past because the climate had long enough to adjust to higher levels of CO2.”
Dr Sime said she and others in the US were now planning to do more research to try to work out how long it took the Western Antarctic ice sheet to melt.
She stressed that the past was only an indication of what might happen in the future, not what would certainly happen."