The Great Barrier Reef (GBR) is the largest contiguous coral reef system in the world. Carbonate chemistry studies and flux quantification within the GBR have largely focused on reef calcification and dissolution, with relatively little work on shelf-scale CO2 dynamics. In this manuscript, we describe the shelf-scale seasonal variability in inorganic carbon and air-sea CO2 fluxes over the main seasons (wet summer, early dry and late dry seasons) in the GBR. Our large-scale dataset reveals that despite spatial-temporal variations, the GBR as a whole is a net source of CO2 to the atmosphere, with calculated air–sea fluxes varying between −6.19 and 12.17 mmol m−2 d−1 (average ± standard error: 1.44 ± 0.15 mmol m−2 d−1), with the strongest release of CO2 occurring during the wet season. The release of CO2 to the atmosphere is likely controlled by mixing of Coral Sea surface water, typically oversaturated in CO2, with the warm shelf waters of the GBR. This leads to oversaturation of the GBR system relative to the atmosphere and a consequent net CO2 release.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Financial support for this study was provided by the Great Barrier Reef Foundation's “Resilient Coral Reefs Successfully Adapting to Climate Change” programme in collaboration with the Australian Government, and the Australian Institute of Marine Science. The authors thank John Pfitzner for his huge efforts in organizing the sample collection and analyse. We thank the crew of the R/V Cape Ferguson and R/V Aquarius for help at sea and Irena Zagorskis and Johnstone Davidson for their help in collecting water samples. Irena Zagorskis is thanked for making the maps included in the manuscript. We also thank Michele Skuza for her huge effort in helping to obtain the dataset. The field chlorophyll a and nutrient data included in the manuscript were obtained with support from the Great Barrier Reef Marine Park Authority, through funding from the Australian Government Reef Program and the Australian Institute of Marine Science. Data from the R/V Cape Ferguson's underway system were sourced from the Integrated Marine Observing System (IMOS) - IMOS is a national collaborative research infrastructure supported by the Australian Government. The R/V Cape Ferguson's underway data were provided by the Australian Ocean Data Network (AODN) Portal (https://portal.aodn.org.au/) and the AIMS Data Catalogue (http://www.aims.gov.au/docs/data/data.html).We thank the associate editor and three anonymous reviewers for their detailed comments and useful suggestions that helped improve the manuscript.