New modeling based on recent data indicates that the Arctic will be ice-free in the summer much earlier than once predicted, according to scientists from National Center for Atmospheric Research (NCAR).
Scenarios run on supercomputers show that the extent of sea ice each September could be reduced so abruptly that, within about 20 years, it may begin retreating four times faster than at any time in the observed record…
The model results indicate that, if greenhouse gases continue to build up in the atmosphere at the current rate, the Arctic’s future ice cover will go through periods of relative stability followed by abrupt retreat. For example, in one model simulation, the September ice shrinks from about 2.3 million to 770,000 square miles in a 10-year period. By 2040, only a small amount of perennial sea ice remains along the north coasts of Greenland and Canada, while most of the Arctic basin is ice-free in September. The winter ice also thins from about 12 feet thick to less than 3 feet.
The research team points to several reasons for the abrupt loss of ice in a gradually warming world. Open water absorbs more sunlight than does ice, meaning that the growing regions of ice-free water will accelerate the warming trend. In addition, global climate change is expected to influence ocean circulations and drive warmer ocean currents into the Arctic.
“As the ice retreats, the ocean transports more heat to the Arctic and the open water absorbs more sunlight, further accelerating the rate of warming and leading to the loss of more ice,” [NCAR scientist Marika] Holland explains. “This is a positive feedback loop with dramatic implications for the entire Arctic region.”
Arctic Sea Ice Summer Minimum in 2005
From National Oceanic and Atmospheric Administration:
Arctic sea ice extent on September 16, 2005, a summer minimum for 1900-2005. Note the large areas of open water north of Alaska and Siberia which are already occurring in the Summer Arctic.
Picture from the University of Illinois.
The color scale shows concentration of sea ice; magenta is 100%.
