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Public Radio's Environmental News Magazine (follow us on Google News)


Air Date: Week of

By looking at whaling records, an Australian researchers has reported the dramatic finding that the once stable Antarctic seasonal sea ice shrunk twenty-five percent in the 1950's and 1960's. The report in the journal Nature lends credence to fears that sudden climate shifts are possible. Steve Curwood spoke with William K. de la Mare from Hobart, Australia.


CURWOOD: Another study reported in the September 4th issue of Nature looks at a different region of the world's climate but comes up with similar disquieting results. The Antarctic has been warming as a region by as much as 4 degrees over the past few decades. But until recently, few records were made of the vast floes of sea ice that surround the frozen continent in winter. But William K. de la Mare, a researcher with Australia's Department of the Environment, came up with the ingenious idea of looking at old whaling records, since whales like to feed right at the edge of the sea ice. He joins us on the line from Hobart, Tazmania. Dr. de la Mare, what exactly did you find?

DE LA MARE: The whaling records show that the Antarctic sea ice has retreated by about 2.8 degrees of latitude, or about 300 kilometers. And rather abruptly, beginning in the mid-1950s, and the retreat was virtually over by the early 1970s.

CURWOOD: Now, how much of this sea ice is there?

DE LA MARE: Altogether, now, there's about 18 million square kilometers of sea ice. And my study shows that about 25% of that has disappeared. And to put that into perspective, that's about three quarters of the area of the continental United States.

CURWOOD: You did research on whaling records to see about the difference in sea ice in the Antarctic. Why did you pick whaling records?

DE LA MARE: Well in fact there are very few scientific observations of anything to do with the Antarctic before the mid-1950s. The whaling records are quite unique, because they stretch back to the early 1930s, and whaling was in fact the most widespread human activity in Antarctica for most of this century.

CURWOOD: Now, these records were collected by whaling ship captains for the purpose of catching whales and not for scientific research. How much stock can we put in the accuracy of these reports?

DE LA MARE: Well, basically, whaling skippers were required to record the position of each whale caught. And there's no particular reason why they would in any way misreport that information. And in fact the correlations between other direct observations on the sea ice and the whaling observations bear out that they're reasonably accurate representations of where the sea ice age was.

CURWOOD: Now, this decline occurred very quickly, just over the space of about 20 years?

DE LA MARE: That's correct, yeah.

CURWOOD: Why do you suppose it happened so fast?

DE LA MARE: The most likely explanation is that there's been some change in oceanic circulation. But of course, that leaves the question open as to what would have caused changes in oceanic circulation of that kind.

CURWOOD: Does it seem that this would be a natural variability in climate, do you think?

DE LA MARE: It could well be a natural variation. Perhaps one possibility is that it's related in some way to the El Niño phenomenon.

CURWOOD: These changes that you found in the Antarctic sea ice might just be regional changes. This is something that perhaps those of us in the northern hemisphere might not have to worry about, right?

DE LA MARE: It seems to be quite a large-scale phenomenon. And of course, all of the world's oceans are linked. You have been talking before about the Atlantic conveyors. The Antarctic is one of the major engines of world climate, so things that go on in the Antarctic are probably of global significance.

CURWOOD: So even though we're seeing regional temperature changes, regional changes in the ice, this is probably affecting the whole world.

DE LA MARE: It's certainly a possibility, sooner or later, yes.

CURWOOD: I'm wondering if your research shows that climate is less likely to change slowly, and in a fashion that will be easy for humans to respond to, and more likely to change rather abruptly.

DE LA MARE: Yes, I think there is [else?] showing that changes can be quite abrupt, and quite substantial. That shows that there are processes which go on that we don't really understand very well. And so in fact to improve our climate models and our predictions about future climate, this poses some questions for us which in the end might be very informative. It would be indeed an irony that the widespread slaughter of whales gave us some important insights into how to better predict the future climate, and therefore how better to manage our own activities. Particularly when we did such a poor job of managing our activities with regard to the whales themselves.

CURWOOD: Well, I want to thank you for taking this time with us today.

DE LA MARE: No trouble at all.

CURWOOD: William K. de la Mare is with the Australian Antarctic Division of the Department of the Environment, and author of the article that appeared on September 4th in Nature magazine.



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