New Zealand's icy visitors - past and present

New Zealand's icy visitors - past and present

Scour marks of the seabed were probably made by an iceberg measuring between 2 and 5 km long.

November saw some unusual visitors to New Zealand waters, with several icebergs reaching the South Island’s east coast. NIWA oceanographer Dr Mike Williams estimated that the bergs probably came from the Ronne Ice Shelf on the other side of Antarctica. Isotope analysis by Dr Russell Frew at Otago University has since confirmed this as the most likely source.

NIWA’s multibeam acoustic survey equipment has detected evidence of much older bergs on the Chatham Rise. The scour marks on this image of the seabed were probably made by an iceberg measuring between 2 and 5 km long (similar or slightly larger than the largest berg sighted in November) during the last Ice Age, about 20 000 years ago, says NIWA marine geologist Dr Scott Nodder.

The evidence was captured from NIWA’s deepwater research vessel Tangaroa during the inaugural voyage of the Government’s Ocean Survey 20/20 programme last August.

For more information, see our iceberg information sheet at www.niwascience.co.nz/pubs/mr/archive/2006-11-28-1.