New satellite data has revealed that the Arctic is melting at a “frightening rate” due to excessive heat caused by human emissions of greenhouse gases.
Late-season Arctic multi-year sea ice — ice that persists for multiple years — was about 50 centimeters (1.6 feet) thinner in 2021 than it was in 2019, according to data. figures, a decline of around 16% in just three years. It is replaced by less permanent seasonal sea ice that melts completely each summer.
Over the past 18 years, winter sea ice in the Arctic Ocean has lost a third of its volume – a staggering figure that may have been underestimated in the past, according to research. This is the first study to use years of satellite data to estimate both ice thickness and snow depth at the summit.
“Arctic snow depth, sea ice thickness and volume are three very difficult measurements to obtain,” says polar scientist Ron Kwokfrom the University of Washington.
“The main finding for me is the remarkable loss of Arctic sea ice volume in winter – a third of the volume of winter ice lost in just 18 years – which has accompanied a widely reported loss of old and thick Arctic sea ice and a end-of-summer ice extent decline.”
The data comes from the ICESat-2 and CryoSat-2 radar satellites in orbit around the Earth.
What makes the study significant is how it combines LiDAR technology from ICESat-2, launched three years ago, and radar technology from CryoSat-2. While LiDAR uses laser pulses and radar uses radio waves, they both detect objects (in this case, snow and ice) based on the reflections returned to them.
Without this data, it is difficult to judge the thickness of the ice, due to how snow can weigh down the ice and change the way it floats in the ocean. Using climate records to estimate snow depth in the past, scientists overestimated sea ice thickness by up to 20 percent or 20 centimeters (0.7 feet), according to the study.
Multi-year ice is known to be thicker and therefore more resistant to melting than seasonal ice – you can think of it as a sort of reservoir for the Arctic.
As it depletes and is replaced by seasonal ice, the overall thickness and volume of Arctic sea ice is also expected to decline rapidly.
“We didn’t really expect to see this decline, for the ice to be this thin in just three short years,” he added. says polar scientist Sahra Kacimifrom the Jet Propulsion Laboratory at the California Institute of Technology.
Combining previous records from the old ICESat satellite to look back over 18 years, the researchers estimate that around 6,000 cubic kilometers (1,439 cubic miles) of winter ice volume was lost during that time.
That the past three years have seen a sharp decline is also concerning. Less ice means massive disruption of ecosystems. This could possibly alter the essential ocean currents we all rely on, and most likely also accelerate the climate change happening all around us.
Meanwhile, it’s promising that the new ICESat-2 satellite, launched in 2018, is performing as expected, and we’re getting more data on Arctic ice levels than ever before – even if it makes for grim reading.
“Current models predict that by the middle of the century we can expect ice-free summers in the Arctic, when older ice, thick enough to survive the melt season, will be gone.” he added. said Kacimi.
The research has been published in Geophysical Research Letters.