ABSTRACT At the Last Glacial Maximum (LGM), about 21,000 years before present, land-based ice sheets held enough water to reduce global mean sea level by 130 metres1. Yet after decades of

study, major uncertainties remain as to the distribution of that ice2. Here we test four reconstructions of North American deglacial ice-sheet history3,4,5,6 by quantitatively connecting

them to high-resolution oxygen isotope (δ18O) records from the Gulf of Mexico7,8,9,10,11 using a water mixing model12. For each reconstruction, we route meltwater3,4,5,6 and seasonal

runoff13,14,15,16 through the time-evolving Mississippi drainage basin, which co-evolves with ice geometry3,4,5,6 and changing topography as ice loads deform the solid Earth and produce

thought5,12,19. In contrast, the three reconstructions based on glacial isostatic adjustment3,4,5 overpredict the δ18O-based post-LGM meltwater volume by a factor of 1.6 to 3.6. The fourth

reconstruction6, which is based on ice physics, has a low enough Mississippi-routed meltwater discharge to be consistent with δ18O constraints, but also contains the largest LGM North

American ice volume. This suggests that modelling based on ice physics may be the best way of matching isotopic records while also sequestering enough water in the North American ice sheets

to match the observed LGM sea level fall1. Access through your institution Buy or subscribe This is a preview of subscription content, access via your institution ACCESS OPTIONS Access

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subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS RAPID NORTHERN HEMISPHERE ICE SHEET MELTING DURING THE PENULTIMATE DEGLACIATION Article Open

access 02 July 2022 MELTWATER PULSE 1A SEA-LEVEL-RISE PATTERNS EXPLAINED BY GLOBAL CASCADE OF ICE LOSS Article 18 February 2025 MULTIPLE EPISODES OF ICE LOSS FROM THE WILKES SUBGLACIAL BASIN

DURING THE LAST INTERGLACIAL Article Open access 18 April 2023 CHANGE HISTORY * _ 30 OCTOBER 2013 In the print version, a citation to ref. 1 in the first sentence is inadvertently missing;

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sediment concentrations. _Sedimentology_ 48, 465–478 (2001) ADS  Google Scholar  Download references ACKNOWLEDGEMENTS We thank F. He, B. Otto-Bliesner and Z. Liu for supplying their

TraCE-21K general circulation model outputs. The Climate Prediction Center Merged Analysis of Precipitation (CMAP) precipitation data were provided by the NOAA/OAR/ESRL PSD from their

website at http://www.esrl.noaa.gov/psd/. A.D.W. was supported by the US Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program, and by the US

National Science Foundation Graduate Research Fellowship under grant number DGE 1144083. J.X.M. acknowledges support from the Canadian Institute for Advanced Research and Harvard

University. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, 1560 30th Street, Boulder,

Colorado 80303, USA, Andrew D. Wickert & Robert S. Anderson * Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA, Jerry

X. Mitrovica * College of Marine Science, University of South Florida, 140 7th Avenue South, St Petersburg, Florida 33701, USA , Carlie Williams Authors * Andrew D. Wickert View author

publications You can also search for this author inPubMed Google Scholar * Jerry X. Mitrovica View author publications You can also search for this author inPubMed Google Scholar * Carlie

Williams View author publications You can also search for this author inPubMed Google Scholar * Robert S. Anderson View author publications You can also search for this author inPubMed 

Google Scholar CONTRIBUTIONS A.D.W. built and ran the drainage basin analysis routine, compiled and corrected the δ18O data, performed the data–model comparisons, and interpreted the

results. J.X.M. provided the global sea level model outputs and post-processing software. C.W. produced a large part of the δ18O data. R.S.A. assisted with idea development. A.D.W. wrote the

manuscript, with input and suggestions from R.S.A., J.X.M. and C.W. CORRESPONDING AUTHOR Correspondence to Andrew D. Wickert. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no

competing financial interests. EXTENDED DATA FIGURES AND TABLES EXTENDED DATA FIGURE 1 MELTWATER DISCHARGE HISTORIES COMPUTED FROM EACH OF THE FLOW-ROUTED ICE MODELS. For comparison, the

δ18Oivc-sw data have been converted to meltwater discharge using the mixing model (equation (1)). The negative discharge shown in the data indicates that the LIS was growing from

precipitation inputs during the Port Bruce Readvance24, significantly reducing net Mississippi discharge (precipitation minus evapotranspiration, minus ice sheet growth) during that time.

The modern mean Mississippi discharge, for reference, is 16,790 m3 s−1 (ref. 38). POWERPOINT SLIDES POWERPOINT SLIDE FOR FIG. 1 POWERPOINT SLIDE FOR FIG. 2 POWERPOINT SLIDE FOR FIG. 3 SOURCE

DATA SOURCE DATA TO FIG. 1 RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Wickert, A., Mitrovica, J., Williams, C. _et al._ Gradual demise of a thin

southern Laurentide ice sheet recorded by Mississippi drainage. _Nature_ 502, 668–671 (2013). https://doi.org/10.1038/nature12609 Download citation * Received: 18 June 2013 * Accepted: 28

August 2013 * Published: 30 October 2013 * Issue Date: 31 October 2013 * DOI: https://doi.org/10.1038/nature12609 SHARE THIS ARTICLE Anyone you share the following link with will be able to

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