Tasman Glacier is the largest glacier in New Zealand, and one of several large glaciers which flow south and east towards the Mackenzie Basin from the Southern Alps in New Zealand's South Island. At 23.5 kilometres in length, Tasman Glacier is still New Zealand's longest glacier, despite shrinking considerably from the 1990s onwards. It is as much as 4 kil…Tasman Glacier is the largest glacier in New Zealand, and one of several large glaciers which flow south and east towards the Mackenzie Basin from the Southern Alps in New Zealand's South Island. At 23.5 kilometres in length, Tasman Glacier is still New Zealand's longest glacier, despite shrinking considerably from the 1990s onwards. It is as much as 4 kilometres wide and 600 metres thick, and lies entirely within the borders of Aoraki / Mount Cook National Park. The glacier covers an area of 101 square kilometres and starts at a height of 3,000 metres above sea level. Snowfall during the winter and spring seasons may accumulate up to 50 metres. After the summer melt, 7 metres may remain in the high altitude glacier head.