Haupapa / 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. Geography At in length, Tasman Glacier is still New Zealand's longest glacier, despite shrinking considerably from the 1990s onwards. It is as much as wide and thick, and lies entirely within the borders of Aoraki / Mount Cook National Park. The glacier covers an area of and starts at a height of above sea level. Snowfall during the winter and spring seasons may accumulate up to . After the summer melt, may remain in the high altitude glacier head. The Tasman flows south west from Hochstetter Dome and Mount Elie De Beaumont alongside the southern slopes of The Minarets and south along the eastern flank of New Zealand's two highest mountains, Mount Tasman and its higher southern neighbour Aoraki / Mount Cook. Although its upper reaches are snow-covered, rocks carried by the glacier are exposed by ablation along its course, and the lower glacier is entirely rock-covered. The rock cover helps insulate the ice from the sunlight and slows down the melting process. Tributaries in the lower parts are the Rudolf Glacier, Forrest Ross Glacier, named after Forrestina Ross), Kaufmann Glacier, Haast Glacier, Hochstetter Glacier, and Ball Glacier. The glacial terminal lake is met by the meltwater of the Murchison Glacier, which approaches from the northeast and flows alongside the Tasman Glacier outside the moraine wall. The waters of Tasman Lake flow into the Tasman River and flow south joining the Hooker River draining the proglacial lakes on the Hooker and Mueller Glaciers. The Tasman River exhibits a braided characteristic, and flows south into Lake Pukaki. They eventually flow into the Waitaki River and to the Pacific Ocean north of Oamaru. Recent retreat The glacier remained at a constant in length for all of its recorded history in the 20th century before starting its current period of rapid melting in the 1990s. Between 2000 and 2008 alone, the glacier terminus receded 3.7 km. Since the 1990s the terminus has retreated about a year on average. The glacier is now in a period of faster retreat where the rate of retreat is calculated to be between each year. It is estimated that the Tasman Glacier will eventually disappear and the terminal Tasman Lake will reach a