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

==== 9.6.2.5 Last Deglacial Transition: Meltwater pulse 1A ====

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During Meltwater pulse 1A (MWP-1A), GMSL ''very likely'' ( ''medium confidence'' ) rose by 8–15 m ( [[#Liu--2016|Liu et al., 2016]] ). Consistent with AR5, the drivers of this rapid rise remain ambiguous. The spatial patterns of RSL change over this interval are inadequately observed to constrain the relative contributions of the North American and Antarctic ice sheets ( [[#Liu--2016|Liu et al., 2016]] ). Modelling studies of the North American Ice Sheet permit a 3–6 m ( [[#Gregoire--2016|Gregoire et al., 2016]] ) or 6–9 m contribution over the duration of MWP-1A ( [[#Tarasov--2012|Tarasov et al., 2012]] ). Sedimentological evidence ( [[#Weber--2014|Weber et al., 2014]] ; [[#Bart--2018|Bart et al., 2018]] ) provides near-field evidence for an Antarctic contribution, consistent with modelling studies ( [[#Golledge--2014|Golledge et al., 2014]] ; [[#Stuhne--2015|Stuhne and Peltier, 2015]] ), but does not constrain the magnitude of the contribution. A recent statistical analysis of Norwegian Sea and Arctic Ocean sediments suggests a 3–7 m contribution from the Eurasian Ice Sheet ( [[#Brendryen--2020|Brendryen et al., 2020]] ), a possibility not considered in AR5 or the meta-analysis of [[#Liu--2016|Liu et al. (2016)]] . In summary, MWP-1A appears to have been driven by a combination of melt in North America ( ''high confidence'' ), Eurasia ( ''low confidence'' ), and Antarctica ( ''low confidence'' ), but the budget is not closed.

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