Arctic sea-ice simulations suggest ice-free summers before 2050 despite rapidly reduced carbon emissions. Human impact will intensify the risk of cascading climate change consequences still further if emissions aren’t checked.
University of Hamburg researchers have used the increased accuracy afforded by the latest generation of global climate models to predict that the Arctic seas are at risk of becoming ice-free during summer months before 2050. Sooner than previously anticipated.
Currently, the North Pole is covered by sea ice throughout the year. Each summer, the area of the sea ice cover decreases, in winter it grows again. In response to ongoing global warming, the overall area of the Arctic Ocean that is covered by sea ice has rapidly been reduced over the past few decades. This substantially affects the Arctic ecosystem and climate.
A new research study involving 21 research institutes from around the world, coordinated by Dirk Notz from the University of Hamburg, Germany, suggests that during summer months the Arctic Ocean will very likely be ice free before 2050, at least temporally. The efficacy of climate-protection measures will determine how often and for how long. The research paper, Arctic Sea Ice in CMIP6, was published in Geophysical Research Papers.
Results were analysed from 40 different climate models. The simulations used were collected within the Coupled Model Intercomparison Project Phase 6 (CMIP6) and based on so-called SSP Scenarios (shared socio-economic pathways). These models were used to simulate scenarios covering both a rapid reduction of future CO2 emissions and one with largely unchanged future CO2 emissions.
As expected, Arctic sea ice disappeared quickly in summer in these simulations. However, the new study finds that Arctic summer sea ice also disappears occasionally if CO2 emissions are rapidly reduced.
"If we reduce global emissions rapidly and substantially, and thus keep global warming below 2 °C relative to preindustrial levels, Arctic sea ice will nevertheless likely disappear occasionally in summer even before 2050. This really surprised us," said Dirk Notz, who leads the sea-ice research group at University of Hamburg, Germany.
How often the Arctic will lose its sea-ice cover in the future critically depends on future CO2 emissions, the study shows. If emissions are reduced rapidly, ice-free years only occur occasionally. With higher emissions, the Arctic Ocean will become ice free in most years. Hence, humans still have an impact on how often the Arctic loses its year-round sea-ice cover.
A hunting ground and habitat for polar bears and seals, sea-ice also keeps the Arctic cool by reflecting sunlight. Previous research from such institutions as the Yale School of Forestry & Environmental Studies and the University Centre in Svalbard (UNIS) suggest that the loss of sea-ice has significant consequences for the algae bloom and increases sea temperatures, as well as wave and storm activity, breaking up further ice flows and effectively turning Earth's air conditioning unit into a heater.