Development of a Training Set of Contemporary Salt-Marsh Foraminifera for Late Holocene Sea- Level Reconstructions in southeastern Australia

Sophie Williams,Rebecca Bartlett,Roland Gehrels,Patrick Moss,Ed Garrett

doi:10.5334/oq.93

Sophie Williams, Rebecca Bartlett + Show 3 more

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https://doi.org/10.5334/oq.93

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Journal: Open Quaternary	Publication Date: Jun 30, 2021
Citations: 8	License type: cc-by

Affiliation: University of York, University of Queensland

Abstract

We collected contemporary foraminiferal training sets from two salt marshes to enable more precise and accurate proxy historical sea-level reconstructions from southeastern Australia. Combined with an existing training set from Tasmania, this new regional set consists of 112 samples and 16 species of foraminifera, of which 13 are agglutinated. Cluster analyses group the regional training set into a high–elevation cluster, dominated by Trochamminita salsa, a mid–elevation cluster, dominated by Entzia macrescens and Trochammina inflata, and a mid–low elevation cluster dominated by Miliammina fusca and tidal-flat species. We develop transfer functions using local and regional training sets and assess their performance. Our resulting site-specific and chosen regional models are capable of predicting sea level with decimetre-scale precision (95% confidence intervals of 0.12–0.22 m). These results are comparable to other examples from around the world. When developing regional training sets, we advocate that the similarity in the environmental settings (particularly salinity) should be assessed as an alternative way of grouping sites, rather than simply using spatial proximity. We compare our findings with global results and conclude that salt marshes along microtidal coasts yield models with the lowest vertical uncertainties. Studies with the lowest uncertainties are located in the western Pacific and the western Atlantic, whereas those from the eastern Atlantic generally have larger tidal ranges and carry larger vertical uncertainties. Our models expand the existing region available for sea-level reconstruction and can be used to generate new late Holocene sea-level reconstructions across southeastern Australia.

Highlights

Proxy-based palaeo sea-level reconstructions usefully complement historical tide-gauge data (Kopp et al 2016) as they expand our knowledge of sea-level change beyond instrumental records and can be used to validate instrumental records where both overlap
We establish new training sets using data collected from a total of four transects at Lutregala salt marsh in the southwest of Tasmania (43.299°S, 147.307°E) and Wapengo salt marsh located in southern New South Wales (36.593°S, 150.009°E) (Figure 1)
4.2 MULTIVARIATE ANALYSES 4.2.1 Partitioning Around Medoids Analysis Combining samples from Lutregala, Wapengo, and the previously published site at Little Swanport (Callard et al 2011) into a regional training set, we find that partitioning around medoids (PAM) analysis groups samples into three clusters (Figure 4)

Summary

Introduction

Proxy-based palaeo sea-level reconstructions usefully complement historical tide-gauge data (Kopp et al 2016) as they expand our knowledge of sea-level change beyond instrumental records and can be used to validate instrumental records where both overlap. Proxy data are important in the Southern Hemisphere as tide-gauge records are sparse and often short compared to those in the Northern Hemisphere (Holgate et al 2013). Both proxy and tide-gauge sea-level data have shown that, globally, the 19th to 20th century sea-level acceleration is larger than any acceleration over the preceding 3000 years (Kopp et al 2016). Grenfell et al 2012); these Southern Hemisphere salt marshes are shallow and are composed of a stratigraphy not very susceptible to compression (Brain et al 2012)

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