Holocene Relative Sea-Level Histories of Far-Field Islands in the Mid-Pacific

Holocene relative sea-level (RSL) data from far-field islands in the mid-Pacific have been used to validate the ice-melting histories of glacial isostatic adjustment (GIA) models. However, a lack of quality control in the reconstruction of RSL hinders the understanding of regional variability that can constrain ice-equivalent sea-level changes. Here, we present a standardised database of Holocene RSL data from five regions in the mid-Pacific (Cook Islands, Tuamotu Islands, Christmas (Kiritimati) Island, Gilbert Islands and Fiji). We categorised the data as high or low quality based on the susceptibility of samples to age and/or elevation errors. Of the 614 data points that were reviewed, 25% were rejected and 100 sea-level index points (SLIPs) were reinterpreted as limiting data. The new database consists of 141 SLIPs and 262 marine and 56 terrestrial limiting data points reconstructed from a variety of sea-level indicators (e.g., coral microatolls, mangrove peat, beachrock, and beach ridges), of which 71% provide high-quality constraints on RSL. The early to mid Holocene RSL evolution in the Cook Islands, Gilbert Islands and Fiji are poorly constrained due to a lack of high-quality SLIPs and limiting data during this period. The Tuamotu Islands provided the only record of early to mid Holocene evolution of RSL, indicating rapid RSL rise from between-22.9 m and-15.2 m at-9.0 ka to between-0.2 m and 0.5 m by-6.5 ka, at rates as high as 9.8 & PLUSMN; 5.1 mm/a, with a slowdown in the rate of RSL rise sometime between-8.2 ka and-6 ka. The Christmas (Kiritimati) Island record indicates stable RSL within-1.5 m of present-day levels over the past-6.6 ka. In the late Holocene, the Cook Islands record suggests a gradual fall in RSL over the past-2.9 ka at rates below 0.1 & PLUSMN; 4.3 mm/a. SLIPs at Fiji also indicate a slight fall in RSL at rates of less than 0.5 & PLUSMN;-4.4 mm/a at-4 ka, following which RSL fell from above 0.9 mat-3 ka to between-0.3 m and 0.6 m by-2.5e-2.1 ka. We highlight the importance of standardisation and quality control to critically evaluate the processes controlling RSL and validate GIA models. Indeed, the new standardised database has impli-cations for the timing of the mid-Holocene highstand, which has been used to support the ICE-4G and ICE-7G_NA models. Due to the poor constraints of data in the mid-Pacific islands, particularly in the early Holocene, there remains no unique solution for a global ice-melting history.& COPY; 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).