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411 results on '"Webster, Jody M."'

4. Reef-insight: A framework for reef habitat mapping with clustering methods via remote sensing

Author

Barve, Saharsh, Webster, Jody M., and Chandra, Rohitash

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence, Computer Science - Computer Vision and Pattern Recognition
Abstract

Environmental damage has been of much concern, particularly in coastal areas and the oceans, given climate change and the drastic effects of pollution and extreme climate events. Our present-day analytical capabilities, along with advancements in information acquisition techniques such as remote sensing, can be utilised for the management and study of coral reef ecosystems. In this paper, we present Reef-Insight, an unsupervised machine learning framework that features advanced clustering methods and remote sensing for reef habitat mapping. Our framework compares different clustering methods for reef habitat mapping using remote sensing data. We evaluate four major clustering approaches based on qualitative and visual assessments which include k-means, hierarchical clustering, Gaussian mixture model, and density-based clustering. We utilise remote sensing data featuring the One Tree Island reef in Australia's Southern Great Barrier Reef. Our results indicate that clustering methods using remote sensing data can well identify benthic and geomorphic clusters in reefs when compared with other studies. Our results indicate that Reef-Insight can generate detailed reef habitat maps outlining distinct reef habitats and has the potential to enable further insights for reef restoration projects.

Published
2023

13. Coral Skeletal Proxy Records Database for the Great Barrier Reef, Australia

Author

Arzey, Ariella Kathleen, primary, McGregor, Helen V., additional, Clark, Tara R., additional, Webster, Jody M., additional, Lewis, Stephen E., additional, Mallela, Jennie, additional, McKay, Nicholas P., additional, Fahey, Hugo W., additional, Chakraborty, Supriyo, additional, Razak, Tries B., additional, and Fischer, Matt J., additional

Published
2024
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14. Bayesreef: A Bayesian inference framework for modelling reef growth in response to environmental change and biological dynamics

Author

Pall, Jodie, Chandra, Rohitash, Azam, Danial, Salles, Tristan, Webster, Jody M., Scalzo, Richard, and Cripps, Sally

Subjects
Statistics - Applications, Computer Science - Computational Engineering, Finance, and Science
Abstract

Estimating the impact of environmental processes on vertical reef development in geological time is a very challenging task. pyReef-Core is a deterministic carbonate stratigraphic forward model designed to simulate the key biological and environmental processes that determine vertical reef accretion and assemblage changes in fossil reef drill cores. We present a Bayesian framework called Bayesreef for the estimation and uncertainty quantification of parameters in pyReef-Core that represent environmental conditions affecting the growth of coral assemblages on geological timescales. We demonstrate the existence of multimodal posterior distributions and investigate the challenges of sampling using Markov chain Monte-Carlo (MCMC) methods, which includes parallel tempering MCMC. We use synthetic reef-core to investigate fundamental issues and then apply the methodology to a selected reef-core from the Great Barrier Reef in Australia. The results show that Bayesreef accurately estimates and provides uncertainty quantification of the selected parameters that represent the environment and ecological conditions in pyReef-Core. Bayesreef provides insights into the complex posterior distributions of parameters in pyReef-Core, which provides the groundwork for future research in this area.

Published
2018

29. Coral Skeletal Proxy Records Database for the Great Barrier Reef, Australia.

Author

Arzey, Ariella Kathleen, McGregor, Helen V., Clark, Tara R., Webster, Jody M., Lewis, Stephen E., Mallela, Jennie, McKay, Nicholas P., Fahey, Hugo W., Chakraborty, Supriyo, Razak, Tries B., and Fischer, Matt J.

Subjects
DATABASES, CORAL reefs & islands, CORALS, DATA libraries, REEFS, KNOWLEDGE gap theory
Abstract

The Great Barrier Reef (GBR), Australia has a long history of palaeoenvironmental coral research. However, it can be logistically difficult to find the relevant research and records, which are often unpublished or exist as 'grey literature'. This hinders researchers' ability to efficiently assess the current state of coral core studies on the GBR and thus identify any key knowledge gaps. This study presents the Great Barrier Reef Coral Skeletal Records Database (GBRCD), which compiles 208 records from coral skeletal research conducted since the early 1990s. The database includes records from the Holocene, from ~8,000 years ago, to the present day; from the northern, central, and southern GBR from inshore and offshore locations. Massive Porites spp. coral records comprise the majority (92.5 %) of the database, and the remaining records are from Acropora , Isopora or Cyphastrea spp. The database includes 78 variables, with Sr/Ca, U/Ca and Ba/Ca the most frequently measured. Most records measure data over 10 or more years and are at monthly or lower resolution. The GBRCD is machine readable and easily searchable so users can find records relevant to their research, for example, by filtering for site names, time period, or coral type. It is publicly available as comma-separated values (CSV) data and metadata files with entries linked by the unique record ID and as Linked Paleo Data (LiPD) files. The GBRCD is publicly available from the NOAA National Center for Environmental Information's Paleoclimate Data Archive at https://doi.org/10.25921/hqxk-8h74 (Arzey et al. 2024). The collection and curation of existing GBR coral research provides researchers with the ability to analyse common proxies such as Sr/Ca across multiple locations and/or examine regional to reef scale trends. The database is also suitable for multi-proxy comparisons and combination or composite analyses to determine overarching changes recorded by the proxies. This database represents the first comprehensive compilation of coral records from the GBR. It enables the investigation of multiple environmental factors via various proxy systems for the GBR, northeastern Australia and potentially the broader Indo-Pacific. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Geology and Geomorphology

Author

Sherman, Clark E., Locker, Stanley D., Webster, Jody M., Weinstein, David K., Riegl, Bernhard M., Series Editor, Dodge, Richard E., Series Editor, Loya, Yossi, editor, Puglise, Kimberly A., editor, and Bridge, Tom C.L., editor

Published
2019
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36. Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum.

Author

Felis, Thomas, McGregor, Helen V, Linsley, Braddock K, Tudhope, Alexander W, Gagan, Michael K, Suzuki, Atsushi, Inoue, Mayuri, Thomas, Alexander L, Esat, Tezer M, Thompson, William G, Tiwari, Manish, Potts, Donald C, Mudelsee, Manfred, Yokoyama, Yusuke, and Webster, Jody M

Abstract

Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and δ(18)O for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 °C larger temperature decrease between 17° and 20°S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

Published
2014

49. Rapid glaciation and a two-step sea level plunge into the Last Glacial Maximum

Author

Yokoyama, Yusuke, Esat, Tezer M., Thompson, William G., Thomas, Alexander L., Webster, Jody M., Miyairi, Yosuke, and Sawada, Chikako

Subjects
Atmospheric carbon dioxide -- Statistics, Environmental research, Glaciation -- Research, Last Glacial Maximum -- Research, Ocean temperature -- Statistics, Ice ages, Corals, Tectonics, Reefs, Climate, Climate models, Carbon dioxide, Ice sheets, Holocene paleogeography, Proxy, Ice caps, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

The approximately 10,000-year-long Last Glacial Maximum, before the termination of the last ice age, was the coldest period in Earth's recent climate history.sup.1. Relative to the Holocene epoch, atmospheric carbon dioxide was about 100 parts per million lower and tropical sea surface temperatures were about 3 to 5 degrees Celsius lower.sup.2,3. The Last Glacial Maximum began when global mean sea level (GMSL) abruptly dropped by about 40 metres around 31,000 years ago.sup.4 and was followed by about 10,000 years of rapid deglaciation into the Holocene.sup.1. The masses of the melting polar ice sheets and the change in ocean volume, and hence in GMSL, are primary constraints for climate models constructed to describe the transition between the Last Glacial Maximum and the Holocene, and future changes; but the rate, timing and magnitude of this transition remain uncertain. Here we show that sea level at the shelf edge of the Great Barrier Reef dropped by around 20 metres between 21,900 and 20,500 years ago, to -118 metres relative to the modern level. Our findings are based on recovered and radiometrically dated fossil corals and coralline algae assemblages, and represent relative sea level at the Great Barrier Reef, rather than GMSL. Subsequently, relative sea level rose at a rate of about 3.5 millimetres per year for around 4,000 years. The rise is consistent with the warming previously observed at 19,000 years ago.sup.1,5, but we now show that it occurred just after the 20-metre drop in relative sea level and the related increase in global ice volumes. The detailed structure of our record is robust because the Great Barrier Reef is remote from former ice sheets and tectonic activity. Relative sea level can be influenced by Earth's response to regional changes in ice and water loadings and may differ greatly from GMSL. Consequently, we used glacio-isostatic models to derive GMSL, and find that the Last Glacial Maximum culminated 20,500 years ago in a GMSL low of about -125 to -130 metres.Details of the drops in sea level associated with glaciation during the Last Glacial Maximum are revealed using a coral proxy from the Great Barrier Reef., Author(s): Yusuke Yokoyama [sup.1] [sup.2] [sup.3] , Tezer M. Esat [sup.4] [sup.5] , William G. Thompson [sup.6] , Alexander L. Thomas [sup.7] , Jody M. Webster [sup.8] , Yosuke Miyairi [...]

Published
2018
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