Last night I watched the ABC's Catalyst programme and the segment "Southern Ocean Sentinel" I was fascinated - firstly as a Science Teacher but also because of the evidence given for Climate Change.
"As well as a thermostat regulating our planet's current climate, scientists believe the Southern Ocean can be a sentinel, an early warning system, of climate tipping points to come. The entire ocean is changing, from the surface to the depths. When seawater freezes it leaves the salt behind. The resulting brine is super-cold, denser, saltier, and sinks to the bottom. That's why it's known as Antarctic Bottom Water. It drives a global current system called the Overturning Circulation." (Source: website)...."At the University of Tasmania, Donna Roberts and her team are searching for signs of ocean acidification. This is what she's looking for — tiny planktonic snails called pteropods. With shells the size of sand grains, they float using their foot like a wing, and catch plankton in nets made of mucus. Dr Donna Roberts "There are millions and billions of tonnes of pteropods in the Southern Ocean and in some regions, particularly the Ross Sea area, there is more pteropods per cubic metre than krill." Pteropods have a really, really fragile shell. All shells are made out of calcium carbonate but not all calcium carbonate is created equal. There's two types and the scientific names are calcite and aragonite.
NARRATION
When CO2 dissolves, it reacts with water to form carbonic acid and carbonate ions, which decreases the pH. Aragonite is more soluble, so any change in pH will affect the growth of aragonite shells first.
Dr Donna Roberts
Now, aragonite is actually in the shells of pteropods and in corals. So corals and pteropods are going to be at risk first if the ocean health and the ocean chemistry changes and it's changing because we're putting carbon dioxide into the water. We weigh the shells individually. Each shell will be about fifteen micrograms.
Mark Horstman
Fifteen millionths of a gram?
Dr Donna Roberts
Yes. I've probably weighed about a couple of hundred thousand shells. We're actually comparing shells from ten years ago to shells from today and what we find is that the shells of today are thirty five percent smaller and more fragile than they were ten years ago.
NARRATION
That means the pteropods of the Southern Ocean, and the food chains they underpin, may be living on borrowed time. Donna can calculate the CO2 levels when they'll basically run out of shell.
Dr Donna Roberts
The tipping point for pteropods in the southern ocean is four hundred and fifty parts per million and we are currently at three hundred and eighty eight so we're heading there rapidly and we, we think from models that we're going to get there in about the winter of 2030." (Source: website)
This would be a terrific report for students in Years 8 - 12 studying Ecology and Climate Change to view and would be a great resource for a scientist role within Climate Change WebQuest.
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