Will the summer sea ice in the Arctic reach a tipping point?  

作　　者：Ola M.Johannessen Elena V.Shalina 

机构地区：[1]Nansen Scientific Society,Bergen,Norway [2]Nansen International Environmental and Remote Sensing Centre,St Petersburg,Russia

出　　处：《Atmospheric and Oceanic Science Letters》2023年第3期58-62,共5页大气和海洋科学快报（英文版）

基　　金：funding support from the Nansen Scientific Society.

摘　　要：The Arctic sea-ice cover has decreased in extent,area,and thickness over the last six decades.Most global climate models project that the summer sea-ice extent(SIE)will decline to less than 1 million(mill.)km^(2) in this century,ranging from 2030 to the end of the century,indicating large uncertainty.However,some models,using the same emission scenarios as required by the Paris Agreement to keep the global temperature below 2°C,indicate that the SIE could be about 2 mill.km^(2) in 2100 but with a large uncertainty of±1.5 mill.km^(2).Here,the authors take another approach by exploring the direct relationship between the SIE and atmospheric CO_(2) concentration for the summer-fall months.The authors correlate the SIE and In(CO_(2)/CO_(2)r)during the period 1979-2022,where CO_(2)r is the reference value in 1979.Using these transient regression equations with an R2 between 0.78 and 0.87,the authors calculate the value that the CO_(2) concentration needs to reach for zero SIE.The results are that,for July,the CO_(2) concentration needs to reach 691±16.5 ppm,for August 604±16.5 ppm,for September 563±17.5 ppm,and for October 620±21 ppm.These values of CO_(2)for an ice-free Arctic are much higher than the targets of the Paris Agreement,which are 450 ppm in 2060 and 425 ppm in 2100,under the IPCC SSP1-2.6 scenario.If these targets can be reached or even almost reached,the "no tipping point"hypothesis for the summer SIE may be valid.

关 键 词：Sea ice ARCTIC Climate change Tipping point 

分 类 号：P731.15[天文地球—海洋科学] P941.62