Editing IPCC:AR6/WGI/Chapter-9 (section)

==== 9.6.2.2 Marine Isotope Stage 11 ====

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The SROCC ( [[#Meredith--2019|Meredith et al., 2019]] ) noted that Greenland may have been ice-free for extensive periods during Pleistocene interglaciations, implying a high sensitivity of the Greenland Ice Sheet to warming levels close to present day. The AR5 ( [[#Church--2013b|Church et al., 2013b]] ) assigned ''medium confidence'' to a Marine Isotope Stage 11 (MIS 11) GMSL of 6–15 m above present, requiring a loss of much of the Greenland and West Antarctic ice sheets, and a possible contribution from East Antarctica. High-resolution multi-proxy sea surface temperature reconstructions and climate model simulations concur that MIS 11 was an extremely long interglacial that exhibited positive annual at 0.5°C ± 1.6 °C ( [[#Irvalı--2020|Irvalı et al., 2020]] ) and summer at 2.1°C–3.4 °C ( [[#Robinson--2017|Robinson et al., 2017]] ) temperature anomalies ( [[#de%20Wet--2016|de Wet et al., 2016]] ). The GMSL was 6–13 m above present ( ''medium confidence'' ) ( [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] ). The Greenland Ice Sheet lost 4.5–6 m ( [[#Reyes--2014|Reyes et al., 2014]] ) or about 6.1 m (3.9–7 m, 95% confidence) sea level equivalent (SLE) by about 7 kyr after peak summer warmth ( [[#Robinson--2017|Robinson et al., 2017]] ), with marine-based ice from AIS ( [[#Blackburn--2020|Blackburn et al., 2020]] ) contributing 6.4–8.8 m SLE at this time ( [[#Mas%20e%20Braga--2021|Mas e Braga et al., 2021]] ). Agreement between GMSL and ice-sheet reconstructions gives ''high confidence'' in identifying a high sensitivity of both ice sheets to the protracted duration of thermal forcing, even at low warming levels ( [[#Reyes--2014|Reyes et al., 2014]] ; [[#Robinson--2017|Robinson et al., 2017]] ; [[#Irvalı--2020|Irvalı et al., 2020]] ; [[#Mas%20e%20Braga--2021|Mas e Braga et al., 2021]] ). Modelled mean mass loss rates for the Greenland Ice Sheet of 0.4 m kyr <sup>–1</sup> during MIS 11 ( [[#Robinson--2017|Robinson et al., 2017]] ) are indistinguishable from recent mass loss rates averaged over 1992–2018 ( [[#9.4.1.1|Section 9.4.1.1]] ). In summary, geological reconstructions and numerical simulations consistently show that past warming levels of &lt;2°C (GMST) are sufficient to trigger multi-metre mass loss from both the Greenland and Antarctic ice sheets if maintained for millennia ( ''high confidence'' ), in agreement with SROCC findings for comparable warming levels during MIS 5e, the Last Interglacial.

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