Transfer functions

Kemp, Andrew C.; Telford, Richard J.

doi:10.1002/9781118452547.ch31

Cited by 33 publications

(56 citation statements)

References 42 publications

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“…We chose the best model by cross‐validations using the leave‐one‐out method. The leave‐one‐out method removes each sample from the dataset, in turn, and then uses the remaining samples to predict the value of the removed sample (Kemp & Telford ). The results of the predictions are shown as cross‐plots between predicted and observed variables (Fig.…”

Section: Resultsmentioning

confidence: 99%

Diatom (Bacillariophyceae) assemblages in salt marshes of south‐central Chile: Relations with tidal inundation time and salinity

Sawai

Nagumo

Namegaya

et al. 2016

Phycological Research

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SUMMARYTo reconstruct sea-level history from changes in tidal environments using diatom assemblages, we need to better understand the relations among brackish diatom assemblages and changing environments along elevational gradients from diverse coastal sites. Our statistical analysis reveals relations between environmental variables and brackish benthic diatom assemblages in the little studied region of south-central Chile. Along four transects across salt marshes at two sites, we identified 224 diatom taxa in 112 samples. Detrended canonical correspondence analysis showed that tidal exposure time index and salinity were appropriately regressed against the abundance of diatom species using unimodal-based methods. Our tests of classical and inverse regressions of weighted average and weighted averaging partial least squares (WA-PLS) showed that WA-PLS resulted in the highest coefficient of determination and the lowest root-mean square of the error of prediction. Our regression will be useful in reconstructing environmental variables from fossil diatom assemblages in Chile.

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Section: Resultsmentioning

confidence: 99%

Diatom (Bacillariophyceae) assemblages in salt marshes of south‐central Chile: Relations with tidal inundation time and salinity

Sawai

Nagumo

Namegaya

et al. 2016

Phycological Research

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“…We determined the length of the modern training set's environmental gradient using detrended correspondence analysis (DCA), executed in the 'Vegan' package for R (Oksanen et al, 2012). The purpose of this analysis was to decide whether linear or unimodal approaches were more appropriate for developing a transfer function to quantify the relationship between assemblages of foraminifera and tidal elevation from the modern training set (Birks, 1995;Juggins and Birks, 2012;Kemp and Telford, 2015). Based on our gradient length exceeding two standard deviations (2.69 standard deviations), we developed a transfer function using a unimodal method (weighted averaging partial least squares; WA-PLS) in the software package C2 (Juggins, 2011).…”

Section: Modern Training Set Of Salt-marsh Foraminiferamentioning

confidence: 99%

“…Sample preparation and counting followed the approach used for surface samples (except for staining with rose Bengal). The WA-PLS transfer function was applied to assemblages of foraminifera within LMR-9 to estimate PME with a sample-specific,~1σ uncertainty (e.g., Juggins and Birks, 2012;Kemp and Telford, 2015). To assess the ecological plausibility of the PME estimations, we measured the dissimilarity between foraminiferal assemblages in core material and their closest modern analogue using the Bray-Curtis distance metric (Jackson and Williams, 2004).…”

Section: Reconstructing Relative Sea Levelmentioning

confidence: 99%

Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida

et al. 2017

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A B S T R A C TTo address a paucity of Common Era data in the Gulf of Mexico, we reconstructed~1.1 m of relative sea-level (RSL) rise over the past~2000 years at Little Manatee River (Gulf Coast of Florida, USA). We applied a regionalscale foraminiferal transfer function to fossil assemblages preserved in a core of salt-marsh peat and organic silt that was dated using radiocarbon and recognition of pollution, 137 Cs and pollen chronohorizons. Our proxy reconstruction was combined with tide-gauge data from four nearby sites spanning 1913-2014 CE. Application of an Errors-in-Variables Integrated Gaussian Process (EIV-IGP) model to the combined proxy and instrumental dataset demonstrates that RSL fell from~350 to 100 BCE, before rising continuously to present. This initial RSL fall was likely the result of local-scale processes (e.g., silting up of a tidal flat or shallow sub-tidal shoal) as saltmarsh development at the site began. Since~0 CE, we consider the reconstruction to be representative of regional-scale RSL trends. We removed a linear rate of 0.3 mm/yr from the RSL record using the EIV-IGP model to estimate climate-driven sea-level trends and to facilitate comparison among sites. This analysis demonstrates that since~0 CE sea level did not deviate significantly from zero until accelerating continuously from~1500 CE to present. Sea level was rising at 1.33 mm/yr in 1900 CE and accelerated until 2014 CE when a rate of 2.02 mm/yr was attained, which is the fastest, century-scale trend in the~2000-year record. Comparison to existing reconstructions from the Gulf coast of Louisiana and the Atlantic coast of northern Florida reveal similar sea-level histories at all three sites. We explored the influence of compaction and fluvial processes on our reconstruction and concluded that compaction was likely insignificant. Fluvial processes were also likely insignificant, but further proxy evidence is needed to fully test this hypothesis. Our results indicate that no significant Common Era sea-level changes took place on the Gulf and southeastern Atlantic U.S. coasts until the onset of modern sea-level rise in the late 19th century.

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“…Studies from the Americas (Jennings & Nelson, ; Gehrels, ; Williams, ; Guilbault et al ., ; Jennings et al ., ; Jennings & Weiner, ; Goldstein & Watkins, ), New Zealand (Hayward et al ., ), Australia (Horton et al ., ) and Great Britain (Horton, ; Edwards & Horton, ) support this notion. Although elevation is the basis for investigating changes in sea level, it must be acknowledged that elevation is not a true environmental variable (Kemp & Telford, ). Elevation itself is not able to exert a controlling influence on modern foraminiferal distributions.…”

Section: Introductionmentioning

confidence: 99%

“…Where ecologists aim to identify and understand the relative importance of controlling variables, palaeoecologists simplify this approach to explain patterns in terms of their relationship with target variables (Edwards & Wright, ), in this case extracting an ‘elevational signal’ from the data. Thus, in developing a transfer function to reconstruct sea‐level change, elevation is accepted as a surrogate variable for true controlling variables (Kemp & Telford, ).…”

Section: Introductionmentioning

confidence: 99%

Environmental controls on the distribution of salt‐marsh foraminifera from the southern coastline of South Africa

Strachan

Finch

Hill

et al. 2015

Journal of Biogeography

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Aim Salt‐marsh foraminifera are widely used as robust sea‐level indicators. High‐resolution Holocene sea‐level reconstructions depend on the accurate characterization of modern foraminifera‐environment relationships representative of a study site. We investigate the relationship between modern foraminiferal assemblage distribution and key environmental variables, viz. elevation above land levelling datum (LLD), sediment grain size, organic content, pH and salinity. We hypothesize that the distribution of modern salt‐marsh foraminifera is primarily controlled by elevation above LLD. Location Knysna and Keiskamma estuaries along the southern coastline of South Africa. Methods Salt‐marsh surface sediment samples (n = 97) were collected along eight intertidal transects with corresponding environmental data (pH, salinity, organic content, sand, silt, clay and elevation). Multivariate ordination analysis (partial redundancy analysis; pRDA) was used to investigate the relationship between living foraminiferal assemblages and environmental controls, after accounting for spatial variability in community composition. Results The pRDA suggests that species composition varied spatially within estuaries, but was strongly influenced by elevation at Keiskamma (r = 0.63) and Knysna (r = −0.75). At Keiskamma, the main gradient in composition was also influenced by salinity (r = −0.63), in an equal and opposite manner to elevation. Composition at Keiskamma was influenced to a much lesser extent by sediment organic content (r = 0.20) and the clay fraction (r = −0.13). At Knysna, pH (r = 0.455) was a secondary determinant of composition, and sediment characteristics covaried with elevation. Main conclusion Elevation was found to be a key environmental variable controlling the distribution of salt‐marsh foraminifera at both estuaries, thereby validating the use of foraminifera as sea‐level indicators. Certain species were particularly sensitive to elevation changes and could thus serve as useful indicators of past sea‐level change. This is an important first step towards the development of high‐resolution sea‐level reconstructions for the South African coastline.

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Transfer functions

Cited by 33 publications

References 42 publications

Diatom (Bacillariophyceae) assemblages in salt marshes of south‐central Chile: Relations with tidal inundation time and salinity

Diatom (Bacillariophyceae) assemblages in salt marshes of south‐central Chile: Relations with tidal inundation time and salinity

Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida

Environmental controls on the distribution of salt‐marsh foraminifera from the southern coastline of South Africa

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