The last interglacial sea-level record of Aotearoa New Zealand

Abstract

Abstract. This paper presents the current state of knowledge of the Aotearoa New Zealand last interglacial (marine isotope stage 5, MIS 5, sensu lato) sea-level record compiled within the framework of the World Atlas of Last Interglacial Shorelines (WALIS) database. A total of 77 relative sea-level (RSL) indicators (direct, marine-limiting, and terrestrial-limiting points), commonly in association with marine terraces, were identified from over 120 studies reviewed. Extensive coastal deformation around New Zealand has prompted research focused on active tectonics, the scale of which overprints the sea-level record in most regions. The ranges of last interglacial palaeo-shoreline elevations are significant on both the North Island (276.8 ± 10.0 to −94.2 ± 10.6 ma.m.s.l., above mean sea level) and South Island (165.8 ± 2.0 to −70.0 ± 10.3 ma.m.s.l.) and have been used to estimate rates of vertical land movement; however, in many instances there is a lack of adequate description and age constraint for high-quality RSL indicators. Identified RSL indicators are correlated with MIS 5, MIS 5e, MIS 5c, and MIS 5a and indicate the potential for the New Zealand sea-level record to inform sea-level fluctuation and climatic change within MIS 5. The Northland Region of the North Island and southeastern South Island, historically considered stable, have the potential to provide a regional sea-level curve, minimally impacted by glacio- and hydro-isostatic adjustment (GIA) and reflecting near-eustatic fluctuations in a remote location of the South Pacific, across broad degrees of latitude; however, additional records from these regions are needed. Future work requires modern analogue information, heights above a defined sea-level datum, better stratigraphic descriptions, and use of improved geochronological methods. The database presented in this study is available open access at this link: https://doi.org/10.5281/zenodo.4590188 (Ryan et al., 2020a).

Drivers of 20th century sea‐level change in southern New Zealand determined from proxy and instrumental records

“…Extrapolation of this short‐term pattern of vertical land motion again does not serve to resolve the difference with the instrumental record, but rather increases the disparity. Furthermore, New Zealand's southern coastline is generally considered tectonically stable over multi‐millennial timescales (Beavan and Litchfield, 2012; Clement et al ., 2016; Ryan et al ., 2021), suggesting that recent uplift may be a transient feature.…”

The Significance of Interseismic Vertical Land Movement at Convergent Plate Boundaries in Probabilistic Sea‐Level Projections for AR6 Scenarios: The New Zealand Case

“…Along 70% of New Zealand's ∼15,000 km coastline from Christchurch clockwise to Hokitika and from Whanganui clockwise to Tauranga (except for Auckland/Waikato segment) estimates of VLM rate from geological archives (spanning the last 125,000 years) are relatively low (<2 mm/y) and are consistent within error of the GNSS rates (Beavan & Litchfield, 2012; Hamling et al., 2022; Houlié & Stern, 2017; Lamb & Smith, 2013; Pillans, 1986; Ryan et al., 2021). In contrast, along ∼30% of the coastline including eastern and southern lower North Island and upper South Island, geodetic data show land surface subsidence has been high this century with rates between 3 and 8 mm/y (Figure 2a).…”

Geomorphological indicators

“…Marine terraces are among the most widely used sea-level indicators for which concerns past interglacials, as they can be preserved for a long time in coastal landscapes. In particular, stairs of marine terraces characterize areas with relevant uplift rates, such as the Pacific Coast of South America (Freisleben et al, 2021) or New Zealand (Ryan et al, 2021).…”