Expedition leader on the tourist ship Spirit of Enderby, Rodney Russ, spotted half of the original iceberg yesterday, 52 nautical miles northeast of Macquarie Island.
He said another large iceberg was identified on radar, which suggested the original iceberg had split in two and the two pieces were drifting north on slightly different courses.
The iceberg spotted yesterday was up to 150 metres long and 25-30 metres high, he said.
Numerous small ice chunks between the two icebergs were a risk to navigation because they floated very low in the water.
Four icebergs off the Auckland Islands, 400km south of Bluff, were spotted heading slowly heading toward New Zealand last week.
Australian scientists reported another mass of 20 icebergs drifting north past Macquarie Island two weeks ago.
Glaciologist Neal Young said satellite images showed a group of icebergs, roughly spread over an area of 1000km by 700km, moving with the ocean current away from Antarctica.
The larger icebergs looked as though they had recently been calved off one of the massive icebergs which originally broke off Antarctica's Ross Ice Shelf and the Ronne Ice Shelf in 2000.
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