Parameterizing the Impact of Seawater Temperature and Irradiance on Dimethylsulfide (DMS) in the Great Barrier Reef and the Contribution of Coral Reefs to the Global Sulfur Cycle

Abstract

Aerosols and clouds play a key role in the Earth's radiative budget and climate. The influence of anthropogenic greenhouse gas (GHG) emissions on the radiative balance is relatively well understood and is estimated to have exerted an average global warming effect of 2.3 W m −2 over the industrial period (IPCC, 2014). Anthropogenic and natural aerosols offset this warming effect by −0.9 W m −2 (−1.9 to −0.1 W m −2) through scattering of shortwave radiation and increasing the albedo, lifetime, and cover of clouds (Andreae, 1995; IPCC, 2014; Twomey, 1974). However, the radiative effects of natural aerosols and their role in climate is complex and less well understood. Approximately 45% of the variance in aerosol radiative forcing is derived

Modelling the influence of coral-reef-derived dimethylsulfide on the atmosphere of the Great Barrier Reef, Australia

“…This method added 0.03 nmol L -1 to the global average seawater concentration and increased global sea-air emissions by 0.3 Tg yr -1 of DMS, representing 1.7% of global DMS emission estimates (Fiddes et al, 2021). This is higher than the estimate of 0.06-0.08 Tg yr -1 of DMS estimated to be released from tropical coral reefs based on field observations (Jones et al, 2018;Jackson et al, 2021).…”

“…However, very few observations were included for coral reef regions and extrapolation did not account for seasonal or spatial variability across coral reef flats and lagoon waters. For this analysis, L11 is modified to include a climatology of DMS w derived from an empirical relationship in the GBR (Jackson et al, 2021), henceforth referred to as the GBR climatology. The GBR climatology calculated in Jackson et al ( 2021) (0.25-degree grid) was scaled up to the model grid by binning the values to a resolution of 1.25 x 1.875 degrees.…”

“…coral-air flux = reef fraction x 22). The fraction of reef cover was calculated as the number of reef pixels within a 0.25-degree grid (as determined in Jackson et al, 2021), using a database of coral reef locations obtained from ReefBase (https://www.refbase.org) in MATLAB R2020a. The estimate of coral cover across the GBR ranged from 0.01-34% within the 0.25 degree-resolution grid.…”

“…The estimate of coral-air DMS flux used in Jackson et al (2021) was scaled up to the model grid by binning the mean values to a resolution of 1.25 x 1.875 degrees. The resulting coralair DMS flux estimate ranged from 0.2-2.6 mmol m -2 d -1 and added an average of 1.4 mmol m -2 d -1 of DMS to the regional seaair flux.…”

“…A parameterization of DMS w in the Great Barrier Reef (GBR), Australia, was recently derived from observational data obtained during Marine National Facility RV Investigator voyage IN2016_V05 (RVI). This parameterization was used to calculate a 19-year climatology of DMS w and DMS flux from the GBR using remotely sensed observations (Jackson et al, 2021). The calculated DMS w climatology reproduced observed seasonal and spatial variability well in the GBR (summarized in Jones et al, 2018) and estimates that the 347,000 km 2 of coral reefs and lagoon waters in the GBR release 0.03-0.05 Tg yr -1 DMS (0.015-0.026 Tg yr -1 S) (Jackson et al, 2021).…”