A new study published in Nature by the University of Wisconsin-Madison and Oregon State University suggests that the West Antarctic ice sheet is not as stable as researchers think it will collapse in the future, leading to a significant rise in sea levels,media reported. The researchers reviewed the last two periods of the Earth’s transition from a state of glaciers to an interglacial period, when the ice sheet covered much of the planet.
In both transitions, this warming was largely driven by the interruption of a process known as the Atlantic Trans-Flip Circulation (AMOC).
A modeling methodology was used to collect optimal estimates of melting glaciers and ice sheets and sea level rise, including greenhouse gas concentrations, global temperatures and subsurface ocean temperatures.
Using the Community Climate System Model 3 of the National Centre for Atmospheric Research, more than 25,000 model years were simulated using the conditions and climate reconstruction that were estimated from data collected from around the world.
The study found that the AMOC was reduced by about 7,000 years in one step during the last interglacle transition period. During the transition to the current interglacle ice age (New World), the AMOC restoration lasted only about two-thirds of the time and was carried out in two steps.
But during these two transitions, the reduction of the AMOC led to underground warming, increased sea ice and reduced ocean convection throughout the Atlantic basin. These reduce the heat loss of the surface ocean and increase the seafloor temperature.
The researchers say that while we have known for a long time that sea levels have risen during warmer periods, this study could help us determine why and how this happens, especially as this new study points to the importance of ocean warming in destabilizing the ocean ice sheet.
By 2014, global temperatures were 1 degree Celsius higher than before industrial times, the same level of warming that caused sea level rise during the last inter-ice period. It also means that, in theory, sea levels could rise by six to nine metres in the same amount of global warming.