ICE-5G and ICE-6G models of postglacial relative sea-level history applied to the Holocene coral reef record of northeastern St Croix, U.S.V.I.: investigating the influence of rotational feedback on GIA processes at tropical latitudes

Fossil coral reefs along the northeastern coast of St Croix in the Caribbean Sea provide an 8000 year record of dated and interpreted Holocene sea-level change. We herein compare this record with the predictions of models of glacio-hydro-isostatic adjustment for St Croix and for additional sites at similar latitudes in the Greater and Lesser Antilles region. RSL predictions are based upon the model ICE-5G (VM2), and with a modified model ICE-6G (VM5A), both including and excluding the influence of rotational feedback. Misfits between the modeled sea levels and the local geologic data are most apparent for models without rotational feedback, particularly in the prediction of a +2 to +4 m unsupported mid-Holocene misfit at ∼4 ka, as well as a small-amplitude highstand that extends from 2.5 to 1.5 ka. Incorporation of the influence of rotational feedback provides the best fit to the data, largely eliminating the unsupported mid-Holocene misfit between the data field and the sea-level histories predicted by the models without rotational feedback, and fitting data older than 5 kyr more closely than a previously published latitudinally-averaged sea-level curve for the western Atlantic. The St Croix data therefore demonstrate that rotational influence extends at least 27° further south from its 45° N mid-latitude extremum along the US east coast, and identifies tropical latitudes as influenced by proglacial forebulge collapse. Implications for reef-based sea-level reconstruction include the ability to accurately model sea levels at specific tropical sites with partial Holocene chronologies using the ICE-6G (VM5A) model with rotational feedback. Latitudinally-averaged sea-level curves are therefore of limited use in understanding the relative importance of contributing physical influences on postglacial sea-level history.

► RSL models ICE-5G(VM2); ICE-6G(VM5A) at St Croix tested with 9 kyr coral data. ► Misfits (modeled RSLs vs geologic data) at ∼4 ka decrease with rotational feedback. ► ICE-6G(VM5A) with rotation best accounts for coral data, St Croix and Barbados. ► Tropical latitudes are shown to be influenced by proglacial forebulge collapse. ► ICE-6G(VM5A) with rotation can model RSLs at tropical sites with limited age data.