Indicator: AAT-14 Ice sheet mass balance and sea ice extent

Data

Ice sheet mass balance

Ice sheet mass balance

Source: Davis, C.H. Li, Y, McConnell, J.R, Frey, M.M, & Hanna, E 2005, Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise.

Fig. 1. Elevation change (black circles) time series from 1992 to 2003 for approx. 7.1 x 106 km2 of the East Antarctic ice-sheet interior. The seasonal and inter-annual cycle (blue line) and long-term trend (red line) are modeled as described in the text. The average rate of change (black line) for the entire time period is 1.8 cm/year after adjustment for isostatic uplift. A steady increase in elevation since about 1995 is apparent. The average rate of change from 1995 to 2003 is 2.2 cm/year after adjustment for isostatic uplift.

Ice sheet elevation change rate

Ice sheet elevation change rate

Source: Davis, C.H., Li, Y., McConnell, J.R, Frey, M.M, & Hanna, E 2005, Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise.

Fig. 2. Elevation-change rate (cm/year) from 1992 to 2003 for 8.5 x 106 km2 of the grounded Antarctic ice-sheet interior. Results are shown in 1° x 2° (latitude x longitude) regions, and boundaries of major drainage basins discussed in the text are superimposed.

Sea ice extent

Sea ice extent

Source: Davis, C.H., Li, Y., McConnell, J.R, Frey, M.M, & Hanna, E 2005, Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise.

What the data mean

This indicator relates to two aspects:

  • Ice sheet mass balance - the net increase or decrease in total stored water in the polar ice cap
  • Sea ice extent - a relatively thin, solid layer that forms in the polar oceans which can more than double the size of Antarctica

Ice sheet mass balance

Davis et al (2005) analysed elevation change of the Antarctic ice-sheet interior from 1992 to 2003 as a measure of net mass change in the ice sheet (figures 1 and 2). They used continuous satellite radar altimeter measurements. They measured elevation change over 8.5 million km2 of the grounded Antarctic ice-sheet interior (about 70% of total ice sheet area) as a result of increased snowfall. However, the change in elevation is not consistent across the entire continent. Across East Antarctica it ranges from a slight to moderate to strong thickening, with an overall thickening of 1.8 ± 0.3 cm/year. In contrast, West Antarctica thickening ranges from modest in some areas to strong thinning in others. The overall trend in West Antarctica is a slight thinning of 0.9 ± 0.3 cm/year.

Alley et al (2005) noted that the mass gain in Antarctica is about 33 ± 8 Gt/year but also noted that data gaps exist on the Antarctic Peninsula and near the South Pole.

Source: Alley, R.B., Clark, P.U 2005, Ice-Sheet and Sea-Level Changes.

Source: Davis, C.H., Li, Y., McConnell, J.R., Frey, M.M, & Hanna, E 2005, Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise.

Sea ice extent

No long term satellite data is available for sea ice extent. Scientists have used ice cores from Law Dome to estimate the size of sea ice extent over the period 1850 to 1995. This is being done by measuring the level of methanesulphonic acid (or MSA). MSA is produced from substances released by phytoplankton; the distribution of phytoplankton is associated with sea ice extent.

The MSA ice core record (1850 to 1995) is shown in grey in the figure. The blue line is the long term trend (20 year running mean) of the MSA data. The purple line from 1973 to 1995 is satellite data for sea ice extent.

The data shows that there is little movement in sea ice extent between 1850 and 1950. However there is a dramatic decrease over the last 50 years equating to about 20%. More work is being done to look deeper into the ice core to provide a data for a longer period.

Data Limitations

Nil known

Issues for which this is an indicator and why

Australian Antarctic Territory — Environment - The ice and land 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation.

Winter sea ice is a nursery area for krill which are nurtured by the algae growing on the underside. The more sea ice, the more sea ice algae and therefore the better the krill population survives. Krill play an important part in the food chain with many animals feeding on them including penguins, seals and whales.

Other indicators for this issue:

Atmosphere — Climate variability and change - Greenhouse 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation.

Other indicators for this issue:

Land — Contributions and pressures between the land and the atmosphere - Climate 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation. This indicator therefore had implications for the impacts of climate change on the Australian continent and globally.

Other indicators for this issue:

Inland Waters — Catchment scale influences - Influence of climate variability and change 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation. This indicator therefore had implications for the impacts of climate change on the Australian continent including inland waters biodiversity.

Other indicators for this issue:

Biodiversity — Pressures on biodiversity - Climate variability 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation. This indicator therefore had implications for the impacts of climate change on the Australian continent and biodiversity.

Other indicators for this issue:

Coasts and Oceans — Condition of the ocean and coastal waters - Climatic and carbon dioxide factors 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation. This indicator therefore had implications for the climatic conditions of Australian waters and the oceans more generally.

Other indicators for this issue:

Coasts and Oceans — Contributions and pressures between the coasts and oceans and the atmosphere - Climate and carbon dioxide 

The changes in ice sheets, sea ice and fast ice may be indicators of climate change. In addition, the Antarctic ice sheet and sea ice plays a major role in global climate through its influence on heat exchange between ocean and atmosphere, it assists the formation of Antarctic bottom water which sinks to the depths of the ocean subsequently driving global ocean circulation. This indicator therefore had implications for the pressure of climate change on Australian waters and the oceans more generally.

Other indicators for this issue: