Antarctic ice loss will cause catastrophic sea level rise
Despite being the coldest place on Earth, Antarctica is very vulnerable to global warming and represents the world’s largest source of potential sea level rise. Many of its ice shelves are currently in the process of collapsing and the continent’s land-based ice sheet is melting rapidly. This melt may continue to accelerate if key ice shelves keep breaking off.
Antarctica is larger, colder and less accessible than the Arctic. While direct observational data is scarce (especially in East Antarctica) and satellite records for many metrics are relatively recent, the Antarctic ice sheet serves as a valuable indicator of climate change. Recent studies raise the possibility that the Greenland and Antarctic ice sheets might be far less stable than previously assumed, threatening 6.6 to 16.4 feet of sea level rise within this century. The major uncertainty regarding catastrophic sea level rise due to Antarctic ice loss is when, not if, sea levels will increase dramatically.
What We Know: Overall Trends
Antarctica is melting. Ice and ocean interactions play a central role, where oceans deliver more heat to ice shelves from underneath, causing instability of inland ice and faster rates of ice melt discharge to the sea. While this chain of events is widely accepted as the cause for ongoing ice melt in West Antarctica, the interior regions do not exhibit a long-term trend.
West Antarctica, Ice Sheet
- Trend: Warming and shrinking
- What is physically happening: Ice sheets are flowing off the continent into the ocean faster, likely influenced by warmer ocean water and ice sheet collapse. Melting influences are also evident in the collapse of major Western ice shelves, including the Larsen ice shelf, which disintegrated in 2002. The ice shelf was 220 meters thick and is believed to have existed for 12,000 years. Warming over time caused gradual stresses and fractures, which culminated in a sudden breakup.
- Why it matters: Land ice melt contributes to sea level rise. The collapse of sea ice can accelerate land ice melting, as ice shelves stem the flow of glaciers into the sea.
West Antarctica, Sea Ice
- Trend: Shrinking
- What is physically happening: In the winter, negative trends are evident at the tip of the Antarctic Peninsula and the western part of the Weddell Sea. In the summer and autumn, sea ice loss is confined to the Bellingshausen and Amundsen Seas. Warm ocean currents are being driven towards West Antarctica and melting sea ice from below.
- Why it matters: Melting sea ice doesn’t contribute directly to sea level rise, but it is a useful indicator of ocean warming. It also means that land ice will flow into the ocean faster without the sea ice blocking it.
East Antarctica, Ice Sheet
- Trend: Slight growth
- What is physically happening: East Antarctica has gained mass. This could be due to reduced levels of ozone in the upper atmosphere that are strengthening the polar wind vortex and preventing warm air from reaching the region. Briny water, due to its relatively high density and lower freezing temperature, is also slowing the process of ice melt. Finally, warmer temperatures and increased air humidity in the surrounding area have contributed to increased snowfall in East Antarctica. However, this could all be natural variation. In addition, the East Antarctic ice sheet has melted in the past and might be more vulnerable than previously thought.
- Why it matters: Although satellites indicate slight growth in the mass of the East Antarctic ice sheet, it is not substantial enough to counter or offset the larger trend of ice loss in the Antarctic continent overall. Trends in East Antarctica are outliers in that nearly every other part of the globe is consistently warming and melting. Furthermore, the data record is short enough that the trend may simply be natural variation. Overall, East Antarctica is the coldest, most sparsely observed and poorly understood part of the continent.
East Antarctica, Sea Ice
- Trend: Slowly growing (maybe)
- What is physically happening: Compared to West Antarctica, changes in the East Antarctic sea ice are less well understood and studies are mixed.
- Why it matters: It doesn’t tell us much about the bigger picture. The same issues understanding the East Antarctic ice sheet apply to sea ice as well.