Gael Alory, an oceanographer at the Commonwealth Scientific and Industrial Research Organization (CSIRO), firmly believes that the changes in sea temperature he's witnessed over the past 40 years in the Indian Ocean are evidence that global warming is taking place.
"From ocean measurements and by analysing climate simulations we can see there are changes in features of the ocean that cannot be explained by natural variability," says Alory. "These oceanic changes are almost certainly linked to changes in the heat structure of the atmosphere and have led to a rise in water temperatures in the sub-tropical Indian Ocean of around two degrees Celsius.
At the same time, we are seeing changes in ocean circulation in tropical regions as a result of a long-term weakening of the Pacific Ocean trade winds. This affects sea surface temperature in regions relevant to the source and distribution of rainfall across southern Australia," he continued.
A study he carried out with several colleagues from CSIRO provided in the following key findings:
- general warming of the ocean surface demonstrating the effect of rising atmospheric temperatures
- strong warming (about 2Â°C over 40 years) between 40Â°S and 50Â°S down to a depth of 800 m
- sub-surface cooling in the tropics due to deep waters rising closer to the surface.
According to Alory, his research helped confirm the existence of the "Indonesian throughflow," a system of currents that transports water between the oceans through a series of passages in the Indonesian Archipelago. "The cooling is occurring between Australia and Indonesia where the Indonesian throughflow emerges into the Indian Ocean and is linked to the observed weakening of Pacific Ocean trade-winds," he says. In addition, the study's results shined a light on the trends in temperatures and ocean features that characterize the subtropical Indian Ocean.
He attributes most of the changes in ocean circulation, temperatures and wind patterns that have occurred over the last few decades to anthropogenic activities, particularly the production of aerosols, greenhouse gas emissions and ozone depletion. Drawing from models used in the IPCC's most recent report, Alory predicts that further variations in the climate regime will be accentuated by global warming.
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