Dr Mike Williams from NIWA explains why it is difficult to explain where the icebergs originated from that were sighted off the Otago coast.
DR MIKE WILLIAMS
Most of the evidence supports that the icebergs that were off the Otago coast came from the Ross Sea. However, we were able to get a sample of the icebergs and look at the isotope signature. The further south you go in Antarctica, the less heavy oxygen 18 there is in the ice. So the sample suggests that this iceberg came from somewhere that was relatively far north, and that’s incompatible with a Ross Sea origin.
So we have the Ross Sea theory, and then the other theory is that it’s come from the Weddell Sea, which is on the opposite side of Antarctica - and so that would mean that iceberg would have had to have travelled all the way round Antarctica and reached New Zealand.
And people go, “oh but we can track them with -- with satellites.” And we have been able to do that, and that very much supports that they came from due south of New Zealand, but that’s neither the Ross Sea nor the Weddell Sea. So this is a classic scientific question of how do you reconcile these 2 pieces of evidence. And the answer is probably going to be that they’ve come from a third place where -- which is consistent with both pieces of evidence.