CryoSat uncovers 2% ice loss in mountain glaciers27th Apr 2023
A European Space Agency (ESA) satellite has led scientists to discover that glaciers around the world have lost 2% of their ice within a decade. ESA’s CryoSat satellite, which launched into space in 2010 and measures the thickness of polar sea ice and ice sheets in Greenland and Antarctica, found that mountain glaciers lost 2720 gigatonnes between 2010 and 2020, mostly due to higher temperatures.
While the CryoSat satellite, which carries a radar altimeter to measure the height of ice surfaces cannot typically measure ice thickness on mountain glaciers due to the rough terrain, the scientists used a new technique to discover the detail of these glaciers and were able to quantify the loss. The breakthrough from these scientists also highlights the potential need for a long-term satellite that measures the ice loss of mountain glaciers.
Glaciers are an important part of the world’s ecosystem, and ones formed on mountains, in particular, are built by snowfall that accumulates over time without melting. They store a significant amount of the world’s freshwater and have even helped farmers irrigate their crops. But due to the effects of climate change, glaciers – in particular, mountain glaciers – are melting, and contribute to the rising sea levels.
Scientists from Earthwave UK, a company that provides satellite data analysis, found that the main driver of this ice loss is the interaction of the atmosphere with warmer temperatures, creating the massive 2720 gigatonne depletion.
“This can be imagined as a giant ice cube, bigger than Europe’s highest mountain, which is quite shocking,” said Livia Jakob, the Chief Scientific Officer, and co-founder of Earthwave. “Importantly, we also found that air temperature, which causes the ice surface to melt, accounts for 89% of this ice loss.”
The remaining 11% is due to ‘ice discharge, which is associated with glaciers that stop at coasts where warmer ocean waters thin the front of the ice flow, according to ESA.
The study also found that in regions where the ocean is changing quickly, like Barents and Kara Seas, ocean interaction there is responsible for most of the ice loss.
How did CryoSat help?
While there are several satellites studying ice loss around the world, understanding the depth of mountain glaciers is limited, and there is no specific satellite mission dedicated to it.
“I’m sure most people have seen photographs taken at different times that show how a glacier terminus has retreated over time. And we can see this from satellite images too,” said Dr Noel Gourmelon, scientific director and co-founder of Earthwave. “But we need to measure how a glacier’s volume is changing to really make sense of what is happening.”
The CryoSat satellite carries the first SAR Interferometric Radar Altimeter onboard, which measures changes in ice sheets and floating ice in polar oceans. It does this by sending microwave pulses to monitor the height of these ice sheets. However, on its own, the instrument is “too course to measure and monitor mountain glaciers”, ESA said. Therefore, the scientists developed a new technique for processing the data.
“Some years ago, we developed a technique of processing CryoSat data, called swath processing, which has revolutionised the use of CryoSat data over complex icy terrains. It unveils a wealth of new detail on glaciers,” Dr Gourmelon said. “The relative contribution of decreasing surface mass balance and increasing ice discharge to sea-level change is well known for the Greenland and Antarctic ice sheets. Now we know more about how the atmosphere and ocean are teaming up to melt glaciers. There is still plenty of work to do to refine these numbers, and to incorporate this knowledge into our glacier projections.”
Calls for a long-term mountain glacier satellite
While measuring ice loss across the world has become paramount to combating climate change, the study highlights the estimates of mountain glacier mass loss are “limited” due to challenges in mapping these glaciers. “While at the global scale there is general agreement between methods, uncertainties remain large and significant differences exist in regional estimates and in the temporal evolution of glacier loss,” the study claimed.
While there are no plans for a specific satellite to address this issue, there is work still being done. A project led by Earthwave and ESA called the Glacier Mass Balance Intercomparison Exercise, or Glambie, is defining the estimates of glacier mass balance from multiple satellites and in-situ methods.