Franz Josef Glacier

The Franz Josef Glacier is a unique temperate maritime glacier located in Westland Tai Poutini National Park. It sits on the West Coast of New Zealand's South Island. This glacier is part of the Te Wāhipounamu World Heritage Site. Alongside the Fox Glacier to its south, it descends from the Southern Alps to altitudes near sea level.

Unlike many glaciers in temperate zones that melt away, the Franz Josef Glacier persists. This is because it is short and very steep. It flows through a narrow valley that drops quickly to low altitudes. The Waiho River emerges from the glacier's terminal, which is its end point.

The glacier's movement begins at the névé, a large snowfield at its head. This névé sits over 2,000 meters above sea level and covers a large area. The névé receives massive amounts of precipitation, sometimes up to 15 meters of snow per year. As snow accumulates, it becomes highly compacted into thick ice. This heavy ice then flows down a steep valley toward the Tasman Sea. The movement in the upper reaches is remarkably fast, often moving 15 feet or more every day.

Glaciers like this one follow a cyclic pattern of advance and retreat. This cycle is driven by the balance between snowfall and meltwater. If the névé receives increased snowfall, the glacier will advance. If the precipitation falls as rain instead of snow, the glacier will retreat. It takes about five to six years for changes in snowfall to affect the terminus location.

While most New Zealand glaciers shrank due to global warming in the late 20th century, the Franz Josef Glacier showed some unusual behavior. Between 1983 and 1999, it actually grew by 1,420 meters. Scientists believe this was caused by cool years from increased southerly air flow in the Tasman Sea, rather than increased rainfall.

The history of the glacier is rich with both scientific and cultural stories. The Māori name is Te Moeka o Tuawe, meaning "The tears of Hine Hukatere." Oral tradition says Hine Hukatere's tears froze to form the glacier after her lover died in an avalanche. European records first mentioned the glacier in the log of the ship Mary Louisa in 1859. In 1865, geologist Julius von Haast named it after Emperor Franz Joseph I of Austria. Following the Ngāi Tahu Claims Settlement Act 1998, the official name was changed to include the Māori name.

As the glacier moves and changes, it shapes the landscape. Near the end of the last ice age about 18,000 years ago, the glacier reached the coastline. As it retreated, it left behind moraines, which are piles of accumulated rock and ice. These deposits created coastal hills and lakes. For example, Lake Wombat is a kettle lake formed by ice left in a moraine 9,000 years ago. Peters Pool was created in a similar way only 210 years ago. The Waiho Loop is a terminal moraine deposited between 12,000 and 3,000 years ago.

Extreme weather can also cause sudden events called jökulhlaups. These are outbreak floods from water-filled ice tunnels. In December 1965, after 280 mm of rain fell in just two days, the Waiho River broke out of the glacier. This flood carried chunks of ice up to 50 cm across downriver to the Tasman Sea. Heavy rain has also destroyed access bridges in 1989, 1991, and 2019. The retreat of the ice also allows for plant succession. Native forests colonize the bare rock left behind by the retreating ice.

Today, the glacier is a major destination for tourism. In 2017, it saw approximately 700,000 visitors.

Because the terminal face became unstable in 2012, visitors can no longer walk directly to the end. Instead, people use helicopters to fly to the ice or take a strenuous hike up Alex Knob. Those who walk on the ice must use specialized equipment like ice axes and crampons, which are metal spikes that latch onto boots.

Despite its beauty, the glacier faces a difficult future. Scientists predict it could lose 38% of its mass by the year 2100 due to warming.