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Not long ago, 33 major research institutions around the world submitted their outlook for the sea ice coverage in September this year.
Among them, the value submitted by the State Key Laboratory of Numerical Modeling of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) of the Institute of Atmospheric Physics, Chinese Academy of Sciences shows that the sea ice area will be reduced to 3.8 million square kilometers in September, which will be the sea ice area since the observation record The second smallest value is only greater than the record of 3.57 million square kilometers in 2012. The international community is very concerned about when the Arctic summer will be ice-free, that is, the area of sea ice in the Arctic Ocean is less than 1 million square kilometers. Ren Hongli, a researcher at the Chinese Academy of Meteorological Sciences, told the Chinese Journal of Science that this time node may appear in the next 20 to 30 years. However, scientists still dispute when the Arctic will appear ice-free in summer. According to satellite observation data, the coverage of Arctic sea ice is the largest in March and the smallest in September. Not long ago, 33 major research institutions around the world submitted their September Arctic sea ice area outlook, including 16 numerical model prediction results, 14 statistical prediction results, and 3 qualitative analysis results, but the results submitted by each institution are quite different. According to Wei Ke, an associate researcher at the Institute of Atmospheric Physics, Chinese Academy of Sciences, the predicted value submitted by the University of Washington is the smallest, only 3.2 million square kilometers; the second is the predicted value submitted by the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration, which is 3.5 million square kilometers; the predicted value submitted by LASG is 3.8 million square kilometers, and these three sets of data are all less than 4 million square kilometers, far below the median range of all models. The forecasts of the ESPC system of the US Naval Research Laboratory, METNO SPARSE of Norway, and APPLICATE CNRM of France are all significantly higher than the median range of all models. For example, the forecast value of the ESPC system is 6.2 million square kilometers. In this regard, Liu Jiping, a professor at the State University of New York in the United States, pointed out that the Siberian heat wave this spring triggered the early retreat of sea ice along the coast of Russia, resulting in a very small range of sea ice in the Laptev Sea and the Barents Sea. At the same time, this summer, the Arctic experienced abnormally high temperatures. For example, on June 20, the highest temperature in the daytime in the city of Verkhoyansk, Siberia, Russia reached 38°C. This is a rare value, because the highest temperature here during the same period in history was only 22°C. It cannot be ruled out that the Arctic sea ice area in September this year tended to be "below 4 million square kilometers." The "amplifier" of global climate change The area of polar sea ice plays a vital role in the earth system. Sea ice reflects up to 80% of the incident sunlight and plays a role in cooling. The size of the sea ice area modulates the amount of incident sunlight entering the earth system. When the temperature rises due to climate change, the melting of sea ice intensifies, and the incident sunlight in the extreme day can enter the ocean more. The sea absorbs more heat and the temperature rises faster, which in turn leads to a larger-scale sea ice melting. This is a positive feedback process that strengthens each other and acts as an "amplifier" for global climate change. In the process of global warming, the Arctic region's warming rate can reach more than twice the global average. This is called "Arctic amplification" phenomenon, which will exacerbate global warming and the melting of Arctic sea ice. "The area of Arctic sea ice has been reduced by 40% compared to the 1970s, and the total ice volume has been drastically reduced by 70%." Wei Ke said. On September 25, 2019, the United Nations Intergovernmental Panel on Climate Change issued the "Special Report on the Ocean and Cryosphere in Climate Change", which assessed the latest changes, impacts and adaptation strategies of the ocean and cryosphere, reflecting current science The world’s latest understanding of the ocean and cryosphere. The report pointed out that the global ocean and cryosphere changes are accelerating. During the period from 1979 to 2018 when satellite observations were made, the sea ice extent of the Arctic in September decreased rapidly at a rate of about 12.8% every 10 years. The sea ice extent at this stage is at least 1,000 The smallest value in the year. The Arctic sea ice is also continuously thinning. Between 1979 and 2018, the area of thick ice over 5 years has decreased by about 90%. As an "indicator and amplifier" of global climate change, the health and stability of the global cryosphere is the cornerstone of the stability of the climate system. Its rapid ablation will inevitably have a profound impact on the ecosystem, coastline stability and human settlements in alpine regions, and will also further modulate it The global climate system affects the intensity and frequency of extreme events. For example, polar bears, walruses and whales rely on the presence of sea ice to maintain their hunting, breeding and migration habits. A substantial reduction in sea ice will have a profound impact on the ecosystem of the Arctic. "The abnormal changes in the range and area of the Arctic sea ice will profoundly affect the safety of navigation and the ecosystem around the Arctic, and will have an important impact on the evolution of the atmospheric circulation in the middle and low latitudes and the occurrence of extreme weather and climate events." Ren Hongli pointed out. Arctic sea ice prediction is not easy Arctic sea ice prediction can provide scientific basis and reference for global climate change monitoring, Arctic waterway utilization, Arctic resource development, and Arctic environmental assessment. "Now that the prediction of Arctic sea ice is becoming more and more important, we need methods and technologies that can accurately predict Arctic sea ice. However, the prediction of sea ice is still very difficult." Liu Jiping emphasized. He said that in order to make a good prediction, a very complex numerical model needs to be established. This model includes the atmosphere, sea ice, and ocean. The interaction between them must be considered, and a series of very complex mathematical and physical equations must be solved before proceeding. prediction. "We mainly use models to predict Arctic sea ice. The China Meteorological Administration's China Multi-Model Ensemble Prediction System (hermes outlet) can release the Arctic and Arctic sea ice prediction products every month." Ren Hongli said. Another method is satellite remote sensing. Liu Jiping pointed out that only high-resolution satellites can see the morphological evolution of sea ice and provide short-term sea ice monitoring. But high-resolution satellite remote sensing faces great challenges in the polar regions. The monitoring of sea ice covered by clouds greatly compromises the effect of high-resolution visible light and near-infrared satellite remote sensing; microwave satellite remote sensing can penetrate clouds, but the resolution is low. Weike said that formulating reasonable policies and measures to carry out long-term emission reductions and short-term climate change adaptation is what it means to deal with the impacts and risks of climate change.
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