Salt marsh elevation and responses to future sea-level rise in the Knysna Estuary, South Africa

Abstract Peak eustatic sea level (ESL), or minimum ice volume, during the protracted marine isotope stage 11 (MIS11) interglacial at ~420 ka remains a matter of contention. A recent study of high-stand markers of MIS11 age from the tectonically stable southern coast of South Africa estimated a peak ESL of 13 m. The present study refines this estimate by taking into account both the uncertainty in the correction for glacial isostatic adjustment (GIA) and the geographic variability of sea level change following polar ice sheet collapse. In regard to the latter, the authors demonstrate, using gravitationally self-consistent numerical predictions of postglacial sea level change, that rapid melting from any of the three major polar ice sheets (West Antarctic, Greenland, or East Antarctic) will lead to a local sea level rise in southern South Africa that is 15%–20% higher than the eustatic sea level rise associated with the ice sheet collapse. Taking this amplification and a range of possible GIA corrections into account and assuming that the tectonic correction applied in the earlier study is correct, the authors revise downward the estimate of peak ESL during MIS11 to 8–11.5 m.

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Late Holocene sea-level change around Newfoundland

Canadian Journal of Earth Sciences ◽

10.1139/e07-036 ◽

2007 ◽

Vol 44 (10) ◽

pp. 1453-1465 ◽

Cited By ~ 11

Author(s):

Julia F Daly ◽

Daniel F Belknap ◽

Joseph T Kelley ◽

Trevor Bell

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Late Holocene ◽

Sea Level Change ◽

Laurentide Ice Sheet ◽

Change Analysis ◽

Level Change ◽

Rising Sea Level ◽

Holocene Sea Level

Differential sea-level change in formerly glaciated areas is predicted owing to variability in extent and timing of glacial coverage. Newfoundland is situated close to the margin of the former Laurentide ice sheet, and the orientation of the shoreline affords the opportunity to investigate variable rates and magnitudes of sea-level change. Analysis of salt-marsh records at four sites around the island yields late Holocene sea-level trends. These trends indicate differential sea-level change in recent millennia. A north–south geographic trend reflects submergence in the south, very slow sea-level rise in the northeast, and a recent transition from falling to rising sea-level at the base of the Northern Peninsula. This variability is best explained as a continued isostatic response to deglaciation.

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Ecophysiological response of native and exotic salt marsh vegetation to waterlogging and salinity: Implications for the effects of sea-level rise

Scientific Reports ◽

10.1038/s41598-017-18721-z ◽

2018 ◽

Vol 8 (1) ◽

Cited By ~ 14

Author(s):

Shi-Hua Li ◽

Zhen-Ming Ge ◽

Li-Na Xie ◽

Wei Chen ◽

Lin Yuan ◽

...

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Salt Marsh Vegetation ◽

Marsh Vegetation ◽

Ecophysiological Response

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Towards disentangling climatic and tectonic changes of southernmost Africa using strontium isotope stratigraphy and clumped isotope thermometry

South African Journal of Geology ◽

10.25131/sajg.124.0045 ◽

2021 ◽

Author(s):

B. Linol ◽

I. Montañez ◽

A. Lombardo ◽

D. Kuta ◽

D. Upadhyay ◽

...

Keyword(s):

South Africa ◽

Sea Level Rise ◽

Sea Level ◽

Secondary Ion Mass Spectrometry ◽

Isotope Composition ◽

Tectonic Activity ◽

Elemental Ratios ◽

Strontium Isotope Stratigraphy ◽

Clumped Isotope ◽

Global Sea Level

Abstract Upper Cretaceous-Cenozoic marine sequences preserved between 30 and 350 masl across southern South Africa record a complex history of climatic and tectonic changes. In this study, we measure the strontium (Sr) isotope composition of fossil shark teeth, echinoderms, corals and oyster shells to chronostratigraphically constrain the ages of these sequences. The method requires careful petrographic screening and micro-drilling of the samples to avoid possible alteration by diagenesis. To assess palaeoenvironmental effects in the shells we measured the Mg/Ca elemental ratios and O isotope values using electron microprobe analysis (EMPA) and secondary ion mass spectrometry (SIMS). In addition, we employed carbonate clumped isotope thermometry to test palaeotemperatures reconstruction. The analysis of recent to modern stromatolites by clumped isotopes yields an average temperature of 20.2°C, in agreement with present day observations. The fossil oyster shells suggest a warmer (23.0°C) seawater palaeotemperature, possibly due to major deglaciation and sea-level rise during the Neogene. We also find that transgressions occurred above 200 to 350 m elevation during: 1) the Campanian-Maastrichian (~75 Ma); 2) the mid-Oligocene (32 to 26 Ma); and 3) the Messinian-Zanclean (6 to 5 Ma). These three episodes are linked to well-known variations in global sea level and regional tectonic processes that could have affected the continental margin differently. The most recent transgression coincides with a maximum global sea-level rise of ~50 m at ca. 5.3 Ma, and a worldwide plate kinematic change around 6 Ma, which in Eurasia led to the closure of the Mediterranean Sea. In the Eastern Cape of South Africa, the new dates of analyzed oyster shells constrain a minimum uplift rate of ca. 150 m/Myr during this tectonic activity. The results have important implications for robust calibration of relative sea level in southern Africa.

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COARSE CLASTIC TIDAL AND FLUVIAL SEDIMENTATION DURING A LARGE LATE ARCHEAN SEA-LEVEL RISE: THE TURFFONTEIN SUBGROUP IN THE VREDEFORT STRUCTURE, SOUTH AFRICA

Tidalites ◽

10.2110/pec.98.61.0155 ◽

1998 ◽

pp. 155-165 ◽

Cited By ~ 1

Author(s):

B. G. ELS ◽

J. J. MAYER

Keyword(s):

South Africa ◽

Sea Level Rise ◽

Sea Level ◽

Fluvial Sedimentation

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A foraminiferal proxy record of 20th century sea-level rise in the Manukau Harbour, New Zealand

Marine and Freshwater Research ◽

10.1071/mf11208 ◽

2012 ◽

Vol 63 (4) ◽

pp. 370 ◽

Cited By ~ 10

Author(s):

Hugh R. Grenfell ◽

Bruce W. Hayward ◽

Ritsuo Nomura ◽

Ashwaq T. Sabaa

Keyword(s):

New Zealand ◽

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

20Th Century ◽

Tide Gauge ◽

Sediment Accumulation ◽

Proxy Record ◽

Tide Gauge Record ◽

Tidal Salt Marsh

The present study aimed to extract a sea-level history from northern New Zealand salt-marsh sediments using a foraminiferal proxy, and to extend beyond the longest nearby tide-gauge record. Transects through high-tidal salt marsh at Puhinui, Manukau Harbour, Auckland, New Zealand, indicate a zonation of dominant foraminifera in the following order (with increasing elevation): Ammonia spp.–Elphidium excavatum, Ammotium fragile, Miliammina fusca, Haplophragmoides wilberti–Trochammina inflata, Trochamminita salsa–Miliammina obliqua. The transect sample faunas are used as a training set to generate a transfer function for estimating past tidal elevations in two short cores nearby. Heavy metal, 210Pb and 137Cs isotope analyses provide age models that indicate 35 cm of sediment accumulation since ~1890 AD. The first proxy-based 20th century rates of sea-level rise from New Zealand’s North Island at 0.28 ± 0.05 cm year–1 and 0.33 ± 0.07 cm year–1 are estimated. These are faster than the nearby Auckland tide gauge for the same interval (0.17 ± 0.1 cm year–1), but comparable to a similar proxy record from southern New Zealand (0.28 ± 0.05 cm year–1) and to satellite-based observations of global sea-level rise since 1993 (0.31 ± 0.07 cm year–1).

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