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Occurrence and seasonal variability of Dense Shelf Water Cascades along Australian continental shelves. Sci Rep 2020; 10:9732. [PMID: 32546836 PMCID: PMC7298046 DOI: 10.1038/s41598-020-66711-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 05/21/2020] [Indexed: 11/21/2022] Open
Abstract
Transport of water between the coast and the deeper ocean, across the continental shelf, is an important process for the distribution of biota, nutrients, suspended and dissolved material on the shelf. Presence of denser water on the inner continental shelf results in a cross-shelf density gradient that drives a gravitational circulation with offshore transport of denser water along the sea bed that is defined as Dense Shelf Water Cascade (DSWC). Analysis of field data, collected from multiple ocean glider data missions around Australia, confirmed that under a range of wind and tidal conditions, DSWC was a regular occurrence during autumn and winter months over a coastline spanning > 10,000 km. It is shown that even in the presence of relatively high wind- and tidal-induced vertical mixing, DSWCs were present due to the strength of the cross-shelf density gradient. The occurrence of DSWC around Australia is unique with continental scale forcing through air-sea fluxes that overcome local wind and tidal forcing. It is shown that DSWC acts as a conduit to transport suspended material across the continental shelf and is a critical process that influences water quality on the inner continental shelf.
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Jones AR, Doubleday ZA, Prowse TAA, Wiltshire KH, Deveney MR, Ward T, Scrivens SL, Cassey P, O'Connell LG, Gillanders BM. Capturing expert uncertainty in spatial cumulative impact assessments. Sci Rep 2018; 8:1469. [PMID: 29362389 PMCID: PMC5780512 DOI: 10.1038/s41598-018-19354-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 12/19/2017] [Indexed: 11/09/2022] Open
Abstract
Understanding the spatial distribution of human impacts on marine environments is necessary for maintaining healthy ecosystems and supporting 'blue economies'. Realistic assessments of impact must consider the cumulative impacts of multiple, coincident threats and the differing vulnerabilities of ecosystems to these threats. Expert knowledge is often used to assess impact in marine ecosystems because empirical data are lacking; however, this introduces uncertainty into the results. As part of a spatial cumulative impact assessment for Spencer Gulf, South Australia, we asked experts to estimate score ranges (best-case, most-likely and worst-case), which accounted for their uncertainty about the effect of 32 threats on eight ecosystems. Expert scores were combined with data on the spatial pattern and intensity of threats to generate cumulative impact maps based on each of the three scoring scenarios, as well as simulations and maps of uncertainty. We compared our method, which explicitly accounts for the experts' knowledge-based uncertainty, with other approaches and found that it provides smaller uncertainty bounds, leading to more constrained assessment results. Collecting these additional data on experts' knowledge-based uncertainty provides transparency and simplifies interpretation of the outputs from spatial cumulative impact assessments, facilitating their application for sustainable resource management and conservation.
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Affiliation(s)
- Alice R Jones
- The University of Adelaide, School of Biological Sciences and Environment Institute, Adelaide, SA, 5005, Australia.
| | - Zoë A Doubleday
- The University of Adelaide, School of Biological Sciences and Environment Institute, Adelaide, SA, 5005, Australia
| | - Thomas A A Prowse
- The University of Adelaide, School of Biological Sciences and Environment Institute, Adelaide, SA, 5005, Australia
- The University of Adelaide, School of Mathematical Sciences, Adelaide, SA, 5005, Australia
| | - Kathryn H Wiltshire
- South Australian Research and Development Institute, Aquatic Sciences, West Beach, SA, 5024, Australia
| | - Marty R Deveney
- South Australian Research and Development Institute, Aquatic Sciences, West Beach, SA, 5024, Australia
| | - Tim Ward
- South Australian Research and Development Institute, Aquatic Sciences, West Beach, SA, 5024, Australia
| | - Sally L Scrivens
- The University of Adelaide, School of Biological Sciences and Environment Institute, Adelaide, SA, 5005, Australia
| | - Phillip Cassey
- The University of Adelaide, School of Biological Sciences and Environment Institute, Adelaide, SA, 5005, Australia
| | - Laura G O'Connell
- Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, K7L 3N6, Ontario, Canada
- Geology, Southern Illinois University, Carbondale, 62901, Illinois, USA
| | - Bronwyn M Gillanders
- The University of Adelaide, School of Biological Sciences and Environment Institute, Adelaide, SA, 5005, Australia.
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Salamena GG, Martins F, Ridd PV. The density-driven circulation of the coastal hypersaline system of the Great Barrier Reef, Australia. MARINE POLLUTION BULLETIN 2016; 105:277-285. [PMID: 26880128 DOI: 10.1016/j.marpolbul.2016.02.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 01/30/2016] [Accepted: 02/04/2016] [Indexed: 06/05/2023]
Abstract
The coastal hypersaline system of the Great Barrier Reef (GBR) in the dry season, was investigated for the first time using a 3D baroclinic model. In the shallow coastal embayments, salinity increases to c.a. 1‰ above typical offshore salinity (~35.4‰). This salinity increase is due to high evaporation rates and negligible freshwater input. The hypersalinity drifts longshore north-westward due to south-easterly trade winds and may eventually pass capes or headlands, e.g. Cape Cleveland, where the water is considerably deeper (c.a. 15m). Here, a pronounced thermohaline circulation is predicted to occur which flushes the hypersalinity offshore at velocities of up to 0.08m/s. Flushing time of the coastal embayments is around 2-3weeks. During the dry season early summer, the thermohaline circulation reduces and therefore, flushing times are predicted to be slight longer due to the reduced onshore-offshore density gradient compared to that in the dry season winter period.
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Affiliation(s)
- Gerry G Salamena
- College of Marine and Environmental Science, James Cook University, Townsville, Queensland 4811, Australia.
| | - Flávio Martins
- CIMA-EST/UAlg., Campus da Penha, P8000-117, Faro, Portugal
| | - Peter V Ridd
- Marine Geophysics Laboratory, College of Science Technology and Engineering, James Cook University, Townsville, Queensland 4811, Australia
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Alendal G, Drange H, Haugan PM. Modelling of Deep-Sea Gravity Currents Using an Integrated Plume Model. THE POLAR OCEANS AND THEIR ROLE IN SHAPING THE GLOBAL ENVIRONMENT 2013. [DOI: 10.1029/gm085p0237] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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