The West Antarctic Ice Sheet (WAIS) is one of three regions making up Antarctica. The other two are East Antarctica and the Antarctic Peninsula, with the Transantarctic Mountain range dividing east from west. Although much smaller than its neighbour to the east, the WAIS still holds enough ice to raise global sea levels by around 3.3 metres. Therefore, even a partial loss of its ice would be enough to change coastlines around the world dramatically. The long-term stability of the WAIS is of particular concern because it is a “marine-based” ice sheet. As the IPCC’s special report on the ocean and cryosphere in a changing climate (“SROCC”) explains, this means that it sits “upon bedrock that largely lies below sea level and [is] in contact with ocean heat, making [it] vulnerable to rapid and irreversible ice loss”. Analysis published in Nature in 2018 showed that the rate of ice loss from the WAIS had tripled from 53bn tonnes a year during 1992-97 to 159bn tonnes a year in 2012-2017. Antarctica’s contribution to global sea levels is currently dominated by ice loss from Amundsen sea sector glaciers. Sections of the Thwaites and Pine Island glaciers, for example, are thinning at rates of 49 and 45cm per year, respectively, on average over 1992-2017. Research indicates that glaciers in this sector are “undergoing a marine ice sheet instability that will significantly contribute to sea level rise in decades to centuries to come”.
Carbon Brief 10th Feb 2020 read more »
Generally, we think of climate change as a gradual process: the more greenhouse gases that humans emit, the more the climate will change. But are there any “points of no return” that commit us to irreversible change? The “Atlantic Meridional Overturning Circulation”, known as “AMOC”, is one of the major current systems in the world’s oceans and plays a crucial role in regulating climate. It is driven by a delicate balance of ocean temperatures and salinity, which is at risk from being upset by a warming climate. The latest research suggests that AMOC is very likely to weaken this century, but a collapse is very unlikely. However, scientists are some way from being able to define exactly how much warming might push AMOC past a tipping point.
Carbon Brief 11th Feb 2020 read more »