Heard Island glaciers facts for kids

The Heard Island glaciers are huge ice masses found on Heard Island. In 1947, these glaciers covered a large part of the island, about 79% of it. This was an area of 288 square kilometers. However, by 1988, the ice had shrunk by 11%, covering only 257 square kilometers.

These glaciers are part of a special area called the Antarctic Environmental Gradient. This area includes different climates, from cool islands to the very cold and dry Antarctic continent. The glaciers on Heard Island stretch from high up at 2745 meters down to sea level. Some of the ice is as deep as 150 meters!

The glaciers can appear to move quickly. This is because the island has steep slopes and gets a lot of rain and snow. They are very sensitive to changes in the climate, especially global warming. Scientists have been watching these glaciers closely. Measurements taken between 1947 and 1980 show that the glaciers are shrinking, especially on the eastern side. This shrinking is linked to changes in weather patterns.

For example, the Brown Glacier lost 29% of its area between 1947 and 2003. All the glaciers on Heard Island flow down from the volcano Big Ben. Scientists have checked, and the volcano's heat output has not changed. This means the melting is not caused by the volcano getting hotter. Instead, the area has warmed by about 1 degree Celsius over the same time.

Glaciologists (scientists who study glaciers) keep a close eye on the Brown Glacier. They measure its front edge (called the snout) and its surface. This helps them figure out if the glacier is shrinking quickly or in smaller steps. They also measure how much ice the glacier gains or loses. They use special radar to measure the ice thickness. Scientists also watch the weather, especially how strong winds called Foehn winds affect the glacier's size.

In 2009, scientists from the Australian Antarctic Division visited Heard Island. They saw that some glaciers had shrunk by 50 meters in just three years! They also fixed an automatic weather station that had been set up in 2000. Dr. Ian Allison, a glaciologist, says that recent aerial surveys show the ice is melting fast. Also, satellite imagery suggests the island might look bigger due to volcanic activity.

How Heard Island's Glaciers Have Changed

Glacier Changes Before 1955

• Between 1874 and 1902, and again from 1902 to 1929, the glaciers didn't seem to change much.
• By 1947, there was some small shrinking in a few spots. By 1954, this shrinking was happening in many places.
• From 1949 to 1954, big changes happened to the ice above 1500 meters (about 5000 feet) on the southwestern side of Big Ben. This might have been due to volcanic activity.

Glacier Changes Since 1955

• By 1963, a lot of shrinking was clear below 600 meters (about 2000 feet) on almost all glaciers. Smaller shrinking was seen as high as 1500 meters.
• The Winston Glacier shrank by about 1.6 kilometers (one mile) between 1947 and 1963.
• There was a very noticeable shrinking of the ice cliffs on the coast northwest of Spit Bay.
• By 1963, coastal ice cliffs that were 15 meters (50 feet) high had disappeared from the Brown and Stephenson Glaciers. These glaciers now ended about 90 meters (100 yards) inland.
• Since 1955, the Baudissin Glacier on the north coast, the Vahsel Glacier on the west coast, and the Jacka Glacier on the east coast of Laurens Peninsula have all shrunk a lot.
• In 1965, scientists saw signs that two glaciers might be growing again:
  • The Winston Glacier had gotten thicker at its end (called the terminus).
  • Some moraine (rock and dirt left by a glacier) was pushed up at the northeastern edge of the Stephenson Glacier. Similar pushes were seen in 1963 on the north side of the Baudissin Glacier.

Why Glaciers Change Their Size

Volcanic Activity

Volcanic activity might have caused the glacier changes above 1500 meters between 1949 and 1955. However, this activity seems to be small and only in certain areas. It cannot explain why glaciers have shrunk so much everywhere since 1955.

Snow is not good at conducting heat. Also, any meltwater from volcanic heat quickly turns into steam. This means volcanic heat doesn't melt large areas of ice easily. Thin layers of volcanic ash can make the ice darker, which means it absorbs more sunlight and melts faster. But thicker layers of ash and cooled lava can actually protect the ice. They act like insulation against the sun's heat, slowing down melting.

Some of Big Ben volcano's past activities include a major eruption in 1910. Glowing lava was seen in 1950. New steam vents (called fumaroles) were seen above 1500 meters on the southwestern slopes of Big Ben in 1949. These were still active in 1954 but were not seen in 1963 or 1965.

Climatic Change

There is evidence that the wind patterns around Heard Island have changed over the last century. This suggests that climate change is a real reason for the glaciers shrinking. People who hunted seals between 1856 and 1859 reported fewer winds from the southwest and more winds from the north. This was different from what the ANARE observed between 1948 and 1955.

Individual Glacier Changes