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Implications of anomalous relative sea-level rise for the peopling of Remote Oceania

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posted on 2023-05-21, 15:48 authored by Sefton, JP, Kemp, AC, Engelhart, SE, Joanna EllisonJoanna Ellison, Karegar, MA, Charley, B, McCoy, MD
Beginning ~3,500 to 3,300 y B.P., humans voyaged into Remote Oceania. Radiocarbon-dated archaeological evidence coupled with cultural, linguistic, and genetic traits indicates two primary migration routes: a Southern Hemisphere and a Northern Hemisphere route. These routes are separated by low-lying, equatorial atolls that were settled during secondary migrations ~1,000 y later after their exposure by relative sea-level fall from a mid-Holocene highstand. High volcanic islands in the Federated States of Micronesia (Pohnpei and Kosrae) also lie between the migration routes and settlement is thought to have occurred during the secondary migrations despite having been above sea level during the initial settlement of Remote Oceania. We reconstruct relative sea level on Pohnpei and Kosrae using radiocarbon-dated mangrove sediment and show that, rather than falling, there was a ~4.3-m rise over the past ~5,700 y. This rise, likely driven by subsidence, implies that evidence for early settlement could lie undiscovered below present sea level. The potential for earlier settlement invites reinterpretation of migration pathways into Remote Oceania and monument building. The UNESCO World Heritage sites of Nan Madol (Pohnpei) and Leluh (Kosrae) were constructed when relative sea level was ~0.94 m (~770 to 750 y B.P.) and ~0.77 m (~640 to 560 y B.P.) lower than present, respectively. Therefore, it is unlikely that they were originally constructed as islets separated by canals filled with ocean water, which is their prevailing interpretation. Due to subsidence, we propose that these islands and monuments are more vulnerable to future relative sea-level rise than previously identified.

Funding

Micronesia Conservation Trust

History

Publication title

Proceedings of the National Academy of Sciences of The United States of America

Volume

119

Issue

52

Article number

e2210863119

Number

e2210863119

Pagination

1-10

ISSN

0027-8424

Department/School

School of Geography, Planning and Spatial Sciences

Publisher

Natl Acad Sciences

Place of publication

2101 Constitution Ave Nw, Washington, USA, Dc, 20418

Rights statement

Copyright © 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CC BY-NC-ND).https://creativecommons.org/licenses/by-nc-nd/4.0/

Repository Status

  • Open

Socio-economic Objectives

Coastal and estuarine systems and management not elsewhere classified; Effects of climate change on the South Pacific (excl. Australia and New Zealand) (excl. social impacts)

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