Tasman Glacier

The Tasman Glacier, officially known as Haupapa / Tasman Glacier, is the largest glacier in New Zealand.

It is also the longest glacier in the country. This massive body of ice is located entirely within Aoraki / Mount Cook National Park. It flows from the Southern Alps toward the Mackenzie Basin on the South Island. The glacier is notable for its immense width and thickness. It covers a vast area of the landscape. Scientists study this glacier to understand how ice environments change over time.

The glacier begins at a high altitude above sea level. It flows southwest from the Hochstetter Dome and Mount Elie De Beaumont. As it moves, it travels alongside the southern slopes of The Minarets. It also flows along the eastern flanks of two of New Zealand's highest mountains. These are Mount Tasman and Aoraki / Mount Cook. The upper reaches of the glacier are covered in white snow. However, the lower section is covered in rocks. This rock cover provides insulation. It protects the ice from sunlight and slows the melting process. This process is known as ablation, which is the loss of ice through melting.

Several smaller glaciers, called tributaries, feed into the lower parts of the Tasman Glacier. These include the Rudolf, Forrest Ross, Kaufmann, Haast, Hochstetter, and Ball Glaciers. The Murchison Glacier also approaches from the northeast. It flows alongside the Tasman Glacier outside of a moraine wall. A moraine is a ridge of debris or rocks left behind by a glacier. The meltwater from these glaciers eventually forms Tasman Lake. This lake is a proglacial lake, meaning it forms in front of a glacier. The water from Tasman Lake flows into the Tasman River. This river is braided, which means it has many small, winding channels. The water eventually joins the Hooker River and flows into Lake Pukaki. From there, it moves through the Waitaki River to the Pacific Ocean.

The history of the Tasman Glacier shows a significant change in its behavior. During the 20th century, the glacier remained at a constant length. This changed in the 1990s when the glacier began a period of rapid melting. This movement of the glacier end away from its previous position is called retreat. Between 2000 and 2008, the glacier terminus receded by 3.7 km. Since the 1990s, the terminus has retreated by about one kilometer each year on average. Currently, the retreat is even faster. It is calculated to be between 10 and 100 meters every year. Experts estimate the glacier will eventually disappear. They believe the terminal Tasman Lake will reach its maximum size in 10 to 19 years.

Natural events can also cause sudden changes to the glacier. On February 22, 2011, the Christchurch earthquake occurred. This earthquake may have triggered a large calving event. Calving is when large chunks of ice break off from the edge of a glacier. During this event, 30 to 40 million metric tons of ice fell into Tasman Lake. This massive fall of ice created tsunami waves up to 7 meters high. These waves were strong enough to hit boats on the lake. Similar events have happened in the past. They are often caused by buoyancy effects. This happens when high water pressure at the base of the ice and increased lake levels from heavy rain push the ice away.

Tourism has played a role in how people experience the Tasman Glacier. Since the early 1970s, heli-skiing tours have operated on the upper glacier. This involves using helicopters to reach the high ice. The Ball Glacier was once a popular spot for skiing, with national championships held there in the 1930s. However, the glacier has diminished too much to be used safely for skiing now. The loss of ice has also changed how people visit the area. More crevasses, which are deep cracks in the ice, are now exposed. Because snow no longer fills them, guided tours are required for safety. The heli-skiing season is now restricted to July, August, and September.

Many visitors enjoy boat tours on Tasman Lake to see floating icebergs. For safety, boats must stay at least 500 meters away from the terminal face. The terminal face is the front edge of the glacier, which stands approximately 40 meters tall. Hikers can also use the Ball Shelter Track. This path leads along the western side of the glacier. It is separated from the lake by a tall moraine wall. About 6 kilometers into the track, the view opens up. From this high point, visitors can see how wide the rock-covered lower glacier is in the valley.