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Your search keyword '"Margvelashvili, N."' showing total 21 results
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21 results on '"Margvelashvili, N."'

4. CSIRO Environmental Modelling Suite (EMS): scientific description of the optical and biogeochemical models (vB3p0)

Author

Baird ME, Wild-Allen KA, Parslow J, Mongin M, Robson B, Skerratt J, Rizwi F, Soja-Wozniak M, Jones E, Herzfeld M, Margvelashvili N, Andrewartha J, Langlais C, Adams MP, Cherukuru N, Gustafsson M, Hadley S, Ralph PJ, Rosebrock U, Schroeder T, Laiolo L, Harrison D, Steven ADL, Baird ME, Wild-Allen KA, Parslow J, Mongin M, Robson B, Skerratt J, Rizwi F, Soja-Wozniak M, Jones E, Herzfeld M, Margvelashvili N, Andrewartha J, Langlais C, Adams MP, Cherukuru N, Gustafsson M, Hadley S, Ralph PJ, Rosebrock U, Schroeder T, Laiolo L, Harrison D, and Steven ADL

Abstract

Abstract. Since the mid-1990s, Australia's Commonwealth Science Industry and Research Organisation (CSIRO) has been developing a biogeochemical (BGC) model for coupling with a hydrodynamic and sediment model for application in estuaries, coastal waters and shelf seas. The suite of coupled models is referred to as the CSIRO Environmental Modelling Suite (EMS) and has been applied at tens of locations around the Australian continent. At a mature point in the BGC model's development, this paper presents a full mathematical description, as well as links to the freely available code and user guide. The mathematical description is structured into processes so that the details of new parameterisations can be easily identified, along with their derivation. In EMS, the underwater light field is simulated by a spectrally resolved optical model that calculates vertical light attenuation from the scattering and absorption of 20+ optically active constituents. The BGC model itself cycles carbon, nitrogen, phosphorous and oxygen through multiple phytoplankton, zooplankton, detritus and dissolved organic and inorganic forms in multiple water column and sediment layers. The water column is dynamically coupled to the sediment to resolve deposition, resuspension and benthic–pelagic biogeochemical fluxes. With a focus on shallow waters, the model also includes detailed representations of benthic plants such as seagrass, macroalgae and coral polyps. A second focus has been on, where possible, the use of geometric derivations of physical limits to constrain ecological rates. This geometric approach generally requires population-based rates to be derived from initially considering the size and shape of individuals. For example, zooplankton grazing considers encounter rates of one predator on a prey field based on summing relative motion of the predator with the prey individuals and the search area; chlorophyll synthesis includes a geometrically derived self-shading term; and the

Published
2020

20. Impact of catchment-derived nutrients and sediments on marine water quality on the Great Barrier Reef: An application of the eReefs marine modelling system.

Author

Baird ME, Mongin M, Skerratt J, Margvelashvili N, Tickell S, Steven ADL, Robillot C, Ellis R, Waters D, Kaniewska P, and Brodie J

Subjects
Coral Reefs, Environmental Monitoring, Geologic Sediments, Nutrients, Rivers, Water Quality
Abstract

Water quality of the Great Barrier Reef (GBR) is determined by a range of natural and anthropogenic drivers that are resolved in the eReefs coupled hydrodynamic - biogeochemical marine model forced by a process-based catchment model, GBR Dynamic SedNet. Model simulations presented here quantify the impact of anthropogenic catchment loads of sediments and nutrients on a range of marine water quality variables. Simulations of 2011-2018 show that reduction of anthropogenic catchment loads results in improved water quality, especially within river plumes. Within the 16 resolved river plumes, anthropogenic loads increased chlorophyll concentration by 0.10 (0.02-0.25) mg Chl m -3 . Reductions of anthropogenic loads following proposed Reef 2050 Water Quality Improvement Plan targets reduced chlorophyll concentration in the plumes by 0.04 (0.01-0.10) mg Chl m -3 . Our simulations demonstrate the impact of anthropogenic loads on GBR water quality and quantify the benefits of improved catchment management., (Crown Copyright © 2021. Published by Elsevier Ltd. All rights reserved.)

Published
2021
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21. The exposure of the Great Barrier Reef to ocean acidification.

Author

Mongin M, Baird ME, Tilbrook B, Matear RJ, Lenton A, Herzfeld M, Wild-Allen K, Skerratt J, Margvelashvili N, Robson BJ, Duarte CM, Gustafsson MS, Ralph PJ, and Steven AD

Subjects
Animals, Hydrodynamics, Hydrogen-Ion Concentration, Models, Biological, Models, Chemical, Oceans and Seas, Anthozoa metabolism, Calcium Carbonate metabolism, Coral Reefs, Seawater chemistry
Abstract

The Great Barrier Reef (GBR) is founded on reef-building corals. Corals build their exoskeleton with aragonite, but ocean acidification is lowering the aragonite saturation state of seawater (Ωa). The downscaling of ocean acidification projections from global to GBR scales requires the set of regional drivers controlling Ωa to be resolved. Here we use a regional coupled circulation-biogeochemical model and observations to estimate the Ωa experienced by the 3,581 reefs of the GBR, and to apportion the contributions of the hydrological cycle, regional hydrodynamics and metabolism on Ωa variability. We find more detail, and a greater range (1.43), than previously compiled coarse maps of Ωa of the region (0.4), or in observations (1.0). Most of the variability in Ωa is due to processes upstream of the reef in question. As a result, future decline in Ωa is likely to be steeper on the GBR than currently projected by the IPCC assessment report.

Published
2016
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