scholarly journals Sensitivity to species selection indicates the effect of nuisance variables on marine microfossil transfer functions

2018 ◽  
Author(s):  
Lukas Jonkers ◽  
Michal Kučera
Keyword(s):  
Transfer Function ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Transfer Functions ◽  
Planktonic Foraminifera ◽  
Sea Surface ◽  
Species Selection ◽  
Training Set ◽  
Function Models ◽  
Transfer Function Models

Abstract. The species composition of many groups of marine plankton appears well predicted by sea surface temperature (SST). Consequently, fossil plankton assemblages have been widely used to reconstruct past SST. Most applications of this approach make use of the highest possible taxonomic resolution. However, not all species are sensitive to temperature and their distribution may be governed by other parameters. There are thus reasons to question the merit of including information all species, both for transfer function performance and for its effect on reconstructions. Here we investigate the effect of species selection on planktonic foraminifera transfer functions. We assess species importance for transfer function models using a random forest technique and evaluate the performance of models with increasing number of species. Irrespective of using models that use the entire training set (weighted averaging) or models that use only a subset of the training set (modern analogue technique), we find that the majority of foraminifera species does not carry useful information for temperature reconstruction. Less than one third of the species in the training set is required to provide a temperature estimate with a prediction error comparable to a transfer function that uses all species in the training set. However, species selection matters for paleotemperature estimates. We find that transfer function models with different number of species but with the same error may yield different reconstructions of sea surface temperature when applied on the same fossil assemblages. This ambiguity in the reconstructions implies that fossil assemblage change reflects a combination of temperature and other environmental factors. The contribution of the additional factors is site and time specific, indicating ecological and geological complexity in the formation of the sedimentary assemblages. The possibility of obtaining multiple different reconstructions from a single sediment record presents a previously unrecognised source of uncertainty for sea surface temperature estimates based on planktonic foraminifera assemblages. This uncertainty can be evaluated by determining the sensitivity of the reconstructions to species pruning.

scholarly journals Sensitivity to species selection indicates the effect of nuisance variables on marine microfossil transfer functions

2019 ◽  
Vol 15 (3) ◽  
pp. 881-891
Author(s):  
Lukas Jonkers ◽  
Michal Kučera
Keyword(s):  
Transfer Function ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Transfer Functions ◽  
Planktonic Foraminifera ◽  
Sea Surface ◽  
Species Selection ◽  
Training Set ◽  
Function Models ◽  
Transfer Function Models

Abstract. The species composition of many groups of marine plankton appears well predicted by sea surface temperature (SST). Consequently, fossil plankton assemblages have been widely used to reconstruct past SST. Most applications of this approach make use of the highest possible taxonomic resolution. However, not all species are sensitive to temperature, and their distribution may be governed by other parameters. There are thus reasons to question the merit of including information about all species, both for transfer function performance and for its effect on reconstructions. Here we investigate the effect of species selection on planktonic foraminifera transfer functions. We assess species importance for transfer function models using a random forest technique and evaluate the performance of models with an increasing number of species. Irrespective of using models that use the entire training set (weighted averaging) or models that use only a subset of the training set (modern analogue technique), we find that the majority of foraminifera species does not carry useful information for temperature reconstruction. Less than one-third of the species in the training set is required to provide a temperature estimate with a prediction error comparable to a transfer function that uses all species in the training set. However, species selection matters for paleotemperature estimates. We find that transfer function models with a different number of species but with the same error may yield different reconstructions of sea surface temperature when applied to the same fossil assemblages. This ambiguity in the reconstructions implies that fossil assemblage change reflects a combination of temperature and other environmental factors. The contribution of the additional factors is site and time specific, indicating ecological and geological complexity in the formation of the sedimentary assemblages. The possibility of obtaining multiple different reconstructions from a single sediment record presents a previously unrecognized source of uncertainty for sea surface temperature estimates based on planktonic foraminifera assemblages. This uncertainty can be evaluated by determining the sensitivity of the reconstructions to species pruning.

scholarly journals Infra-sample, inter-sample and down-core microvariation in sea-surface temperature estimates obtained from planktonic foraminifera in the NE Atlantic

1997 ◽  
Vol 16 (2) ◽  
pp. 163-174 ◽  
Author(s):  
Brian M. Funnell ◽  
Jane E. Swallow
Keyword(s):  
Transfer Function ◽  
Confidence Interval ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Function Analysis ◽  
Planktonic Foraminifera ◽  
Sea Surface ◽  
Ne Atlantic ◽  
Quantitative Investigation ◽  
Transfer Function Analysis

Abstract. Quantitative investigation of populations of planktonic foraminifera in core-top and down-core (top 10 cm) samples from 14 sites in the NE Atlantic, between 19° to 52°N and 11° to 30°W, have revealed no intra-sample, inter-sample or down-core variability beyond that to be expected on counts of 300 specimens (2 standard deviations, 95% confidence interval). Application of F20 transfer function analysis shows that estimates of sea-surface temperature, based on these counts, fall within a range of ±1.9°C (precision). However, when these estimates are compared with ‘actual’ temperatures within the 1° latitude/longitude squares containing the sites, the estimate errors range as high as ±3.6°C (accuracy). These results indicate there is a continuing need to improve methods for estimating proxy temperatures from planktonic foraminifera, in order to match the requirements of numerical modellers of past climates.

scholarly journals Tropical sea-surface temperature reconstruction for the early Paleogene using Mg/Ca ratios of planktonic foraminifera

2003 ◽  
Vol 18 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Aradhna K. Tripati ◽  
Margaret L. Delaney ◽  
James C. Zachos ◽  
Linda D. Anderson ◽  
Daniel C. Kelly ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Planktonic Foraminifera ◽  
Temperature Reconstruction ◽  
Sea Surface ◽  
Tropical Sea ◽  
Early Paleogene

Coupled Mg/Ca and clumped isotope measurements at IODP Site U1488 confirm absence of Plio-Pleistocene sea surface temperature cooling in the Western Pacific Warm Pool

2020 ◽  
Author(s):  
Niklas Meinicke ◽  
Maria Reimi ◽  
Christina Ravelo ◽  
Nele Meckler
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Planktonic Foraminifera ◽  
Warm Pool ◽  
Western Pacific ◽  
Sea Surface ◽  
Western Pacific Warm Pool ◽  
Pacific Warm Pool ◽  
The Western Pacific

<p>The Western Pacific Warm Pool (WPWP) as a major source of heat and water vapor has a crucial influence on climate dynamics both in the tropics and globally. Yet, there is conflicting proxy evidence regarding the evolution of WPWP temperatures since the Miocene. On the one hand TEX<sub>86</sub> data suggest a gradual cooling by ~2℃ (O’Brian et al., 2014, Zhang et al., 2014) from the Pliocene to today, while faunal (planktonic foraminifera) sea surface temperature estimates (Dowsett, 2007) and Mg/Ca data measured in planktonic foraminifera (Wara et al., 2005) on the other hand indicate the absence of any long-term temperature trends. It has been suggested that Mg/Ca temperatures could on these time scales be biased by long-term changes of the Mg/Ca ratio of seawater (Evans et al., 2016). To test the influence of the proposed seawater changes on Mg/Ca we combined data from two independent temperature proxies, Mg/Ca and clumped isotopes, measured on two species of planktonic foraminifera from IODP Site U1488 in the central WPWP. Our study finds good agreement between both proxies thereby verifying the validity of Mg/Ca records from the WPWP and confirming the absence of a Plio-Pleistocene cooling trend for the WPWP. This finding suggests that the persistent disagreement between foraminifer-based proxies such as Mg/Ca and biomarker data might be caused by different environmental parameters being recorded in the two archives.</p><p> </p><p>References:</p><p>O’Brien CL, Foster GL, Martínez-Botí MA, Abell R, Rae JWB, Pancost RD. High sea surface temperatures in tropical warm pools during the Pliocene. Nature Geoscience. 2014;7(8):606-11.</p><p>Zhang YG, Pagani M, Liu Z. A 12-million-year temperature history of the tropical Pacific Ocean. Science. 2014;344(6179):84-7.</p><p>Dowsett H. Faunal re-evaluation of Mid-Pliocene conditions in the western equatorial Pacific. Micropaleontology. 2007;53(6):447-56.</p><p>Wara MW, Ravelo AC, Delaney ML. Permanent El Nino-like conditions during the Pliocene warm period. Science. 2005;309(5735):758-61.</p><p>Evans D, Brierley C, Raymo ME, Erez J, Müller W. Planktic foraminifera shell chemistry response to seawater chemistry: Pliocene–Pleistocene seawater Mg/Ca, temperature and sea level change. Earth and Planetary Science Letters. 2016;438:139-48.</p>

scholarly journals The Interdependency of the Morphological Variations of the Planktonic Foraminiferal Species Globigerina bulloides in Surface Sediments on the Environmental Parameters of the Southwestern Indian Ocean

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Abhijit Mazumder ◽  
Neloy Khare ◽  
Pawan Govil
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Census Data ◽  
Planktonic Foraminifera ◽  
Morphological Characteristics ◽  
Sea Surface ◽  
Globigerina Bulloides ◽  
Foraminiferal Species ◽  
Ecological Parameters

18 surface sediment samples collected from a north-south transect along the Indian Ocean have been analyzed for planktonic Foraminifera content. Among the other planktonic foraminiferal faunas, Globigerina bulloides was present substantially in all samples. Census data of G. bulloides were measured for different parameters (average size, mean proloculus size, coiling direction, and number of chambers) and a Q-mode cluster analysis was applied on these data. Samples were segregated into two homogeneous clusters, each reflecting particular environmental conditions. Two clusters are as follows: (1) Cluster A, comprised of 6 samples and characterized by the highest range of foraminiferal and ecological parameters, except sea surface temperature and salinity which shows the lowest range, and (2) Cluster B, comprised of 12 samples and characterized by the lowest range of foraminiferal parameters and ecological parameters, except sea surface temperature and salinity which shows the highest range. The study suggests that the ecological parameters are the governing factors for the morphological characteristics of planktonic foraminiferal species G. bulloides.

Sign in / Sign up

Export Citation Format

Share Document