Marine projections of warming and ocean acidification in the Australasian region

Abstract

In response to increasing carbon dioxide emissions the oceans have become warmer and more acidic. In this paper, the ability of Earth System Models to simulate observed temperature and ocean acidification around Australia is assessed. The model results are also compared with observations collected at stations around Australia over recent years to assess how representative the model results are of the coastal domain; and are found to adequately simulate the mean state at most sites.Simulations from the Coupled Model Intercomparison Project 5 (CMIP5) under low, medium and high emissions scenarios (RCPs 2.6, 4.5 and 8.5 respectively) are then used to project how ocean acidification and sea surface temperature will change. Under each of these emissions scenarios the oceans around Australia exhibit warming and continued acidification. However, these changes are quite heterogeneous, with increases of up to +6 K (under RCP 8.5) above the pre-industrial value, projected in areas such as the Tasman Sea. We conclude that the projected changes in SST, aragonite saturation state and pH are likely to profoundly impact marine ecosystems, and the ecosystem services that they provide in the Australasian region.

The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) – Part 2: Historical simulations

“…The CMIP5 models used to assess the ocean response of ACCESS-ESM1 over the historical period in the study. References for all models are provided in Lenton et al (2015). The dataset used here is limited by having no inter-annual or longer timescale variability.…”

“…The models used in this paper are shown in Table 1 with the references provided in Lenton et al (2015). As not all years were available for these simulations, we focussed on the period 1870-2005 and used only the first ensemble member for each ESM.…”

“…As not all years were available for these simulations, we focussed on the period 1870-2005 and used only the first ensemble member for each ESM. In assessing the response of the CMIP5 models, we calculated the median and the 10th and 90th percentiles following Lenton et al (2015). This allows us to both assess how well ACCESS-ESM1 captures the median and whether it falls into the range of existing CMIP5 models.…”

The influence of local sea surface temperatures on Australian east coast cyclones

“…The EAC is a “hot spot” for projected global warming, with SSTs in parts of the Tasman Sea expected to warm by more than 2°C between the 1990s and 2060s [ Oliver et al ., ] and median projected changes by 2090 under RCP8.5 close to 4°C [ Lenton et al ., ]. While global climate models project a decline in extratropical cyclones in Australian latitudes over the coming century [ Dowdy et al ., ; Grieger et al ., ], their resolutions generally inhibit accurate representation of the EAC, with large uncertainty in how changes in SST may affect ECLs in areas such as the Australian east coast.…”

“…Increased SST resolution and improved representation of eddies had little effect on the overall intensity or development of the low, but resulted in shifts in the locations of thunderstorms and peak rainfall, of considerable interest to forecasters. under RCP8.5 close to 4°C [Lenton et al, 2015]. While global climate models project a decline in extratropical cyclones in Australian latitudes over the coming century [Dowdy et al, 2014;Grieger et al, 2014], their resolutions generally inhibit accurate representation of the EAC, with large uncertainty in how changes in SST may affect ECLs in areas such as the Australian east coast.…”