Heard Island glaciers
The Heard Island glaciers covered 79 percent of
A 29% reduction in area of the Brown Glacier from 1947-2003 was observed.[4] The volcano Big Ben, from which all the glaciers drain, has shown no sign of changing geothermal output to cause the melting;[4] a 1 degree Celsius warming has occurred over the same time period.[4] Glaciologists continue to study the Brown Glacier, detailing surveys of the glacier's snout and surface, which determine if glacial retreat is rapid or punctuated.[4]
Measurements on the mass balance of the glacier, as well as more detailed ice thickness measurements using a portable radar echo sounder, were undertaken.[4] Monitoring of climatic conditions continues, with emphasis on the impact of Foehn winds on glacier mass balance.
An expedition by scientists from the Australian Antarctic Division recently visited the volcanic island in 2009, observing glaciers that had retreated 50 metres in three years. Repairs were made to an automatic weather station established in November 2000.[2]
Glacier changes
Changes before 1955
- No apparent change between 1874–1902 or 1902–1929[2]
- Minor recession in a few places by 1947 and widespread by 1954.[2]
- Marked changes occurred in the ice formation above 5000 ft (1500 m) on the southwestern slopes of Big Ben between 1949–1954 (possibly volcanic activity (Padang, 1963)[2]
Changes since 1955
- The major recession in 1963 was obvious below 2000 ft (600 m) on almost all glaciers, and minor recession was evident as high as 5000 ft.
- Winston Glacier retreated approximately one mile (1.6 km) between 1947 and 1963.[2]
- Striking retreat on the coast north-west of Spit Bay.[2]
- Disappearance of coastal ice cliffs 50 ft high off Brown and Stephenson Glaciers by 1963. Glaciers terminated as much as 100 yards inland.[2]
- Marked recession since 1955 of Jacka Glacier on the east coast of Laurens Peninsula.[2]
- 1965 observations suggest a possible readvance of two glaciers:
- overthrust was apparent at the northeastern seaward edge of Stephenson Glacier. Overthrusts had also been seen in 1963 on the north lateral moraine of Baudissin Glacier.[2]
Possible causes of terminus change
Volcanic activity
Volcanic activity may have caused the glacier changes above 5000 ft between 1949 and 1955 but such activity seems to be minor and localized. It cannot explain the widespread
Some of the volcano Big Ben's activities include a major
Southward movement of the Antarctic Convergence
The southward movement of the Antarctic Convergence might cause glacier retreat through a rise in sea and air temperature.[2] However, there is no evidence of a change in the Antarctic Convergence's mean position.[2] Because the Antarctic Convergence in the Kerguelen Islands region is not well known, its position there is the subject of considerable disagreement (Meinardus, 1923; Mackintosh, 1946; Ostapoff, 1965; Soviet Antarctic Expedition, 1966).[2]
Climatic change
Evidence of a probable change in the
Individual glaciers
| Glaciers | Date of change | Changes |
|---|---|---|
| Baudissin | 1955→ | Continuous marked recession[2] |
| Vahsel | 1955→ | Continuous marked recession. Loss of at least 200 vertical feet of ice, with horizontal retreat as indicated by terminal moraines.[2] |
Abbotsmith |
1947→ | Relatively little changes[2] |
| Gotley | 1947→ | Relatively little changes[2] |
| Winston | 1947–1963 | Loss of about 300 feet in thickness as indicated by young moraines flanking the Winston Lagoon; retreated 1 mile[2] |
| Stephenson | 1947–1963 | 50 feet of coastal ice cliff disappeared and terminated 100 yards inland[2] |
| Brown | 1947–1963; 2008 | Similar to the Stephenson Glacier. 50 feet of coastal ice cliff disappeared and terminated 100 yards inland.[2] 29% reduction in area[4] |
| Compton | 1947–1986 | Retreated 1600 metres[6] |
Jacka |
1955→ | Continuous marked recession[2] |
References
- ^ a b "Our subantarctic glaciers: Why are they retreating? :: Australian Antarctic Division". Archived from the original on 2010-12-28. Retrieved 2011-02-03.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab "Australian — Heard Island and McDonald Islands".
- ^ "Search - The Encyclopedia of Earth".
- ^ a b c d e f "Stephenson Glacier retreat, Heard Island – From a Glaciers Perspective".
- ^ "Heard Island glaciers melting away, say scientists - ABC News". Australian Broadcasting Corporation.
- ^ http://journals.cambridge.org/article_S0032247400007099, Ian F. Allison and Peter L. Keage (1986). Recent changes in the glaciers of Heard Island. Polar Record, 23, pp 255-272 (members-only link)