Sea ice within the coastal areas of the Arctic could also be thinning as much as twice as quick as beforehand thought, based on a brand new modelling examine led by UCL researchers.
Sea ice thickness is inferred by measuring the peak of the ice above the water, and this measurement is distorted by snow weighing the ice floe down. Scientists regulate for this utilizing a map of snow depth within the Arctic that’s a long time old-fashioned and doesn’t account for local weather change.
Within the new examine, printed within the journal The Cryosphere, researchers swapped this map for the outcomes of a brand new laptop mannequin designed to estimate snow depth because it varies yr to yr, and concluded that sea ice in key coastal areas was thinning at a charge that was 70% to 100% sooner than beforehand thought.
Robbie Mallett (UCL Earth Sciences), the PhD scholar who led the examine, mentioned: “The thickness of sea ice is a delicate indicator of the well being of the Arctic. It is vital as thicker ice acts as an insulating blanket, stopping the ocean from warming up the environment in winter, and defending the ocean from the sunshine in summer season. Thinner ice can be much less prone to survive throughout the Arctic summer season soften.”
“Earlier calculations of sea ice thickness are based mostly on a snow map final up to date 20 years in the past. As a result of sea ice has begun forming later and later within the yr, the snow on high has much less time to build up. Our calculations account for this declining snow depth for the primary time, and counsel the ocean ice is thinning sooner than we thought.”
Co-author Professor Julienne Stroeve (UCL Earth Sciences) mentioned: “There are a selection of uncertainties in measuring sea ice thickness however we consider our new calculations are a significant step ahead when it comes to extra precisely decoding the information we have now from satellites.
“We hope this work can be utilized to higher assess the efficiency of local weather fashions that forecast the results of long-term local weather change within the Arctic — a area that’s warming at 3 times the worldwide charge, and whose tens of millions of sq. kilometres of ice are important for holding the planet cool.”
To calculate sea ice thickness researchers used radar from the European Area Company’s CryoSat-2 satellite tv for pc. By timing how lengthy it takes for radar waves to bounce again from the ice, they will calculate the peak of the ice above the water, from which they will infer the ice’s complete thickness.
Within the new examine, researchers used a novel snow mannequin beforehand developed by researchers at UCL and Colorado State College, SnowModel-LG, which calculates snow depth and density utilizing inputs similar to air temperature, snowfall and ice movement information to trace how a lot snow accumulates on sea ice because it strikes across the Arctic Ocean. By combining the outcomes of the snow mannequin with satellite tv for pc radar observations, they then estimated the general charge of decline of sea ice thickness within the Arctic, in addition to the variability of sea ice thickness from yr to yr.
They discovered that the speed of decline within the three coastal seas of Laptev, Kara and Chukchi seas elevated by 70%, 98% and 110% respectively, when in comparison with earlier calculations. In addition they discovered that, throughout all seven coastal seas, the variability in sea ice thickness from yr to yr elevated by 58%.
Sea ice within the coastal seas sometimes varies from half a metre to 2 metres thick. More and more, the ice on this area just isn’t surviving the summer season soften. The sooner thinning of sea ice within the coastal Arctic seas has implications for human exercise within the area, each when it comes to transport alongside the Northern Sea Route for a bigger a part of the yr, in addition to the extraction of assets from the ocean ground similar to oil, fuel and minerals.
Mallett mentioned: “Extra ships following the route round Siberia would scale back the gasoline and carbon emissions obligatory to maneuver items around the globe, significantly between China and Europe. Nevertheless, it additionally raises the danger of gasoline spillages within the Arctic, the results of which could possibly be dire. The thinning of coastal sea ice can be worrying for indigenous communities, because it leaves settlements on the coast more and more uncovered to sturdy climate and wave motion from the rising ocean.”
Mallett, Professor Stroeve and co-author Dr Michel Tsamados (UCL Earth Sciences) spent a number of weeks investigating snow and ice within the Arctic onboard the German analysis vessel Polarstern, which explored the central Arctic Ocean in 2019 and 2020.
The examine was funded by the UK’s Pure Setting Analysis Council, the European Area Company (ESA), and the US Nationwide Aeronautics and Area Administration (NASA).