The changing sea around us

The ocean around us, the source of life, is the basis for our future well-being. We will do well to heed what’s happening there. [6 May 2008 | Peter Boyer]

We’ve always known we’re different, down here in little Tasmania.

CSIRO modelling shows a "hot spot" developing off Tasmania's east coast over coming decades. (Data Richard Matear)

CSIRO modelling shows a "hot spot" developing off Tasmania's east coast over coming decades. (Data Richard Matear)

You just have to look at a map of the world. Where much bigger places like Russia, Brazil, Congo, Queensland just blend into the background of their great land masses, Tasmania is there for all to see in a sea of blue.

The  relatively large islands of Tasmania and its trans-Tasman cousin, New Zealand, protrude into waters loosely called the Southern Ocean – a dynamic, storm-tossed system that unites all the major oceans with the world’s largest current, the Antarctic Circumpolar.

Basing the CSIRO’s marine and atmospheric studies in Hobart, with links to Antarctic CRC, University of Tasmania and Australian Antarctic Division research, is a recognition of the special place of Tasmania in the science of this watery planet.

Our oceans are crucially important to life on Earth. They absorb vast quantities of carbon dioxide, and since the start of the Industrial Revolution they’ve been helping to keep atmospheric CO2 at a tolerable level.

This would be good news for us on land if it wasn’t for the fact that these increasing carbon levels in oceans have made seawater more acid, to a point where some species are struggling to survive.

If our present carbon pollution trajectory continues to the end of this century, our oceans will be more acidic than they have been since hundreds of millennia before humans walked the planet. And the rate of change will be greater than anything previous in that time.

The biological implications are enormous, affecting ocean ecosystems from the tinest organism right up to the top of the food chain. From a human perspective, even putting aside overfishing, we will find it increasingly difficult to obtain food from the ocean.

There’s something else that we in Tasmania need to be concerned about. Waters off our island’s east coast are getting warmer. An especially pronounced warming in recent years, when the warm, southerly-flowing East Australia Current extended its reach around the far south of Tasmania, was a clear sign of change.

Based on what we know about past and present patterns, CSIRO computer models show a significant “hot spot” developing over coming decades in the Tasman Sea off Tasmania’s east coast – a possibility that has the concerned attention of Tasmania’s commercial fishing and aquaculture industries.

Unlike warm-blooded humans, the species for which Tasmanian sea fishing is famous – rock lobster, scallops, abalone and many scale fish – prefer their water cold. So do Atlantic salmon.

Warming seas will also change Tasmania’s weather patterns in ways that are still being worked out – one more factor in an unfolding future that is both fascinating and unsettling.

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