Historical reconstruction of ocean acidification in the Australian region
The ocean has become more acidic over the last 200 years in response increasing atmospheric carbon dioxide (CO<sub>2</sub>) levels. Documenting how the ocean has changed is critical for assessing how these changes impact marine ecosystems and for the management of marine resources. Here...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-03-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/1753/2016/bg-13-1753-2016.pdf |
| Summary: | The ocean has
become more acidic over the last 200 years in response increasing atmospheric
carbon dioxide (CO<sub>2</sub>) levels. Documenting how the ocean has changed is
critical for assessing how these changes impact marine ecosystems and for the
management of marine resources. Here we use present-day ocean carbon
observations, from shelf and offshore waters around Australia, combined with
neural network mapping of CO<sub>2</sub>, sea surface temperature, and salinity to
estimate the current seasonal and regional distributions of carbonate
chemistry (pH and aragonite saturation state). The observed changes in
atmospheric CO<sub>2</sub> and sea surface temperature (SST) and climatological
salinity are then used to reconstruct pH and aragonite saturation state
changes over the last 140 years (1870–2013). The comparison with data
collected at Integrated Marine Observing System National Reference Station
sites located on the shelf around Australia shows that both the mean state
and seasonality in the present day are well represented, with the exception
of sites such as the Great Barrier Reef. Our reconstruction predicts that
since 1870 decrease in aragonite saturation state of 0.48 and of
0.09 in pH has occurred in response to increasing oceanic uptake of
atmospheric CO<sub>2</sub>. Large seasonal variability in pH and aragonite saturation
state occur in southwestern Australia driven by ocean dynamics (mixing) and
in the Tasman Sea by seasonal warming (in the case of the aragonite
saturation state). The seasonal and historical changes in aragonite
saturation state and pH have different spatial patterns and suggest that the
biological responses to ocean acidification are likely to be non-uniform
depending on the relative sensitivity of organisms to shifts in pH and
saturation state. This new historical reconstruction provides an important
link to biological observations that will help to elucidate the consequences
of ocean acidification. |
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| ISSN: | 1726-4170 1726-4189 |