| Climate change is the biggest challenge facing human society in the 21st century.Among the five major layers of the Earth system,the cryosphere is highly sensitive to climate change.Monitoring the change of the cryosphere plays an important role in understanding global climate change and more accurately predicting future climate change and its impact.As an important part of the cryosphere,sea ice is an indicator and amplifier of climate change.Sea ice affects the heat exchange between the ocean and the atmosphere,and plays a significant role in climate change research.The Antarctic sea ice zone is a sensitive and key area for global climate and environmental changes.Thus,carrying out research on the volume changes of Antarctic sea ice is of great significance for understanding climate change and improving climate models.At present,passive microwave snow depth model is insufficient for retrieving snow depth on sea ice,and it is not suitable for the domestic Feng Yun-3 satellite of China.In recent years,there is still a lack of understanding of how the snow depth on Antarctic sea ice,sea ice thickness and sea ice volume change,and how climatic variables affect the Antarctic sea ice volume changes.Focusing on the above issues,this study has carried out research in the following aspects:(1)Construction of snow depth model based on bright temperature data of Feng Yun-3At present,the research and application of the brightness temperature data of Chinese passive microwave Feng Yun-3 in Antarctica is still lacking.The classic snow depth on Antarctic sea ice model is based on SSM/I and AMSR-E passive microwave data,and it has poor adaptability to passive microwave data of Feng Yun-3.In this paper,we used the latest Antarctic ASPe Ct observation snow depth data to establish a snow depth inversion model suitable for the domestic Feng Yun-3 passive microwave brightness temperature data.(2)Multi-scale spatio-temporal analysis of Feng Yun-3 derived snow depth and sea ice thicknessCompared to the study of Arctic,there is still a lack of understanding of how the Antarctic sea ice thickness and volume change.This study attempts to use the passive microwave brightness temperature data of the domestic Feng Yun satellite to retrieve the snow depth on Antarctic sea ice,combined with the Cryo Sat-2 radar altimeter data to calculate and retrieve the Antarctic sea ice thickness and sea ice volume.The interannual and monthly scale changes of the entire Southern Ocean and various subregions are analyzed,with a view to obtaining the spatial and temporal distribution characteristics and trends of snow depth on Antarctic sea ice and sea ice thickness in recent years.(3)Antarctic sea ice volume change and its coupling with typical climatic variablesAt present,in the study of the relationship between sea ice changes and climate mode and climate varibles,the main focus is on the study of sea ice area changes,while the study of Antarctic sea ice volume changes and large-scale climate mode changes is still lacking.This paper combines the sea ice thickness based on the newly constructed snow depth and the sea ice concentration based on the inversion of the passive microwave bright temperature data of Feng Yun-3 to calculate the Antarctic sea ice volume,and further analyze the time-series changes of sea ice area and sea ice volume And change trends.This study attempts to analylize a variety of large-scale climate mode(SOI,MEI,IOD,SAM)and Antarctic sea ice volume changes for correlation analysis and explore the influences which different climate mode has on Antarctic sea ice volume change.This paper also uses singular value decomposition(SVD)to analyze the spatiotemporal changes of typical Antarctic climate varibles(sea surface temperature,air temperature,net solar radiation and sea level pressure)and their relationship with the Antarctic sea ice volume change,with a view to obtaining coupling relation between the Antarctic sea ice volume change and typical climate varibles.The main conclusions are:(1)Construction of snow depth model for Feng Yun-3Using the latest Antarctic cruising snow depth data,the Feng Yun-3 snow depth inversion model was constructed.The evaluation results of the newly constructed model using the in-situ data show that this model is superior to the classic Markus98 snow depth model.The newly constructed snow depth model has better accuracy in the snow depth applied to the inversion of the MWRI bright temperature data of Feng Yun-3.The newly constructed snow depth model significantly improves the usability of the bright temperature data of Feng Yun-3 in the remote sensing inversion of snow depth in Antarctica.(2)Spatio-temporal variations of snow depth on Antarctic sea iceFrom April 2012 to October 2018,the monthly average snow depth of the Antarctic fluctuated between 10-15 cm.The average monthly maximum snow depth of the Antarctic is 14.4 cm in September 2015,and the minimum monthly snow depth is9.9 cm in April 2012.The average snow depth declined slightly from April to May,rising month by month from May to September,and then decreased again in October.The average sea ice surface snow depth over many years presents a relatively obvious seasonal variation.During the study period,the change trend of snow depth on Antarctic sea ice was 0.3 cm/a,showing a slightly increasing trend.Among the snow depths of the various sub-regon,the Weddell Sea area has the largest annual average(14.8 cm),and the Bellingshausen Sea and Amundsen Sea areas have the largest annual growth rate(0.51 cm/a).Through the spatial analysis of the snow depth of the on Antarctic sea ice,it is found that during the study period,the rate of change of the snow depth of the Antarctic sea ice surface area presents different changes in different regions.The snow depth in the central area of West Weddell Sea and the Ross Sea shows a downward trend,while the Bellingshausen and Amundsen Seas show an upward trend.(3)Spatio-temporal variations of Antarctic sea ice thicknessThrough the airborne observation of the water outlet height data,the optimal water outlet height estimation parameter based on the lowest point elevation method of Cryo Sat-2 altimetry data is determined:after the elimination of 0.8 times the standard deviation,the 10 km data segment along the rail is selected,and Take a minimum of 5%of the sample points and take the average as the local sea level.The monthly average sea ice thickness fluctuates between 220-270 cm across the Antarctic.During the study period,from April 2012 to August 2015,the thickness of sea ice showed an increasing trend with a change trend of 4.23 cm/a,while from August 2015 to October 2018,the thickness of sea ice showed a decreasing trend.The trend is-3.95 cm/a.Throughout the study period,the annual sea ice thickness changes in the Ross Sea and Weddell Sea areas were-1.43 cm/a and-1.65 cm/a,respectively.The Bellingshausen and Amundsen Seas,the Indian Ocean region and the Pacific region have a upward trend.In general,the decline rate of the sea ice thickness in the Antarctic is greater than that in the Antarctic sea ice.The decline rate of the sea ice thickness in the Weddell and Ross Sea regions is the largest.(4)Relationship between Antarctic sea ice volume and climatic variablesDuring the study period,sea ice volume presented a decreasing trend from April2012 to October 2018.The change trend of sea ice area in the whole Antarctic year is-26650 km~2/a,and the change trend of sea ice volume is-439.1 km~3/a.From April to August,the average volume of sea ice increases month by month,and decreases from August to October.The volume of sea ice in the Antarctic year increased from 2012 to2014,while the volume of sea ice in the Antarctic decreased from 2014 to 2017,and the volume of sea ice in the Antarctic increased slightly from 2017 to 2018.During the study period,the area of sea ice and the thickness of sea ice both showed a decreasing trend,which together caused the decrease in the volume of Antarctic sea ice.The contribution rate of sea ice area and sea ice thickness to the volume change of Antarctic sea ice is 88.3%and 11.7%respectively.In terms of large-scale climatic mode and changes in Antarctic sea ice volume,there is the large correlation between changes in the volume of the Antarctic sea ice and the multivariate Enso index(MEI)(R=0.47).In terms of sea ice volume change in sub-sea areas,the Weddell Sea volume change has the largest correlation with the MEI index(R=0.61);the Indian Ocean sea ice volume change has the largest correlation with the SAM index(R=0.35);the Pacific Ocean sea ice volume change has the greatest correlation with the SAM index(R=0.16);the sea ice volume change of Ross Sea has the greatest correlation with the MEI index(R=0.20);the change in sea ice volume in the Bellingshausen and Amundsen Seas has the greatest correlation with the IOD index(R=0.26).In terms of typical climatic elements and changes in the of Antarctic sea ice volume,air temperature anomalies have the greatest correlation with anomalies of Antarctic sea ice volume(R=0.39).The increasing trends of sea surface temperature(SST),sea ice temperature(T2M),net solar radiant flux(SSR)in the Antarctic sea ice area,and the decreasing trend of sea level pressure(SLP)are consisten with the Antarctic sea ice volume decreased trend.The SVD analysis results of the Antarctic sea ice typical climate field and Antarctic sea ice volume show that,among the four typical climate varibles,the time coefficient(principal component)of the leading spatial mode of air temperature(T2M)between the Antarctic sea ice volume have the largest correlation coefficient(R=0.89).The correlation between the time coefficient of the leading spatial mode of SLP and the time coefficient of Antarctic sea ice volume(R=0.675)is the smallest. |
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