| As an important part of the earth system,the polar environment is closely related to the changes of the global ecosystem.Sea ice is an important feature of the two poles,and the study of its change is an important part of the global climate change research.It is also an important data support and security guarantee for the scientific research of the Arctic and Antarctic in China.Most of the current studies shown that the polar sea ice changes in the opposite directions,while the Arctic sea ice decreased sharply,the Antarctic sea ice shown a slight increase trend.Due to the obvious global warming in recent years,how the sea ice changes in the Antarctic and the Arctic respectively are still a problem to be discussed.The sea ice concentration,the whole sea ice extent,the first-year ice extent,the multi-year ice extent,the melting and freezing cycle are the important parameters to study the sea ice in the polar region.Whether there is internal relationship and mutual influence between the changes of them,and how the differences and similarities of the changes of the parameters between the Antarctic and the Arctic are the focus of the sea ice research at this stage.Based on the daily sea ice concentration data of 1979-2018 provided by the NSIDC,this thesis studies the inversion of sea ice parameters in the Antarctic and Arctic.In terms of research design,the Antarctic and the Arctic are studied respectively,then the comprehensive research and comparative analysis are carried out;in terms of research variables,the whole sea ice concentration,the whole sea ice extent,first-year ice extent,the multi-year ice extent,the melting and freezing cycle are studied respectively to obtain their change characteristics,and then the comparative study is carried out to explore their mutual change relationship;on the spatial scale,the overall analysis and local sea zone comparison are discussed;on the time scale,the annual average,monthly average(extremum monthly)and daily average(extremum daily)are studied,and the 1979-2018 and typical small time periods(2009-2018,2014-2018)are used to explore the characteristics of sea ice changes in the Antarctic and the Arctic.The results show that:(1)From 1979 to 2018,the Arctic sea ice showed a sharp decrease trend.The sea ice concentration,the whole sea ice extent(-0.0478×10~6km~2/year)and the multi-year ice extent(-0.0927×10~6km~2/year(-19.03%/10 years))all decreased,while the first-year ice increased(0.0393×10~6km~2/year).In recent years,the reduction of multi-year ice is more obvious,and the reduction of multi-year ice is 25.45%in the ten years of 2009-2018.(2)From 1979 to 2018,the Antarctic sea ice showed a slight increase trend.The sea ice concentration,the whole sea ice extent(0.0106×10~6km~2/year)and the first-year ice(0.0117×10~6km~2/year)all increased,while the multi-year ice extent(-0.0028×10~6km~2/year)decreased in a weak trend.(3)From 1979 to 2018,the overall sea ice extent of the polar region decreased at the rate of 0.0372×10~6km~2 per year,with an average decreased of-1.38%every 10years,and from 2014 to 2018,it decreased at the rate of 2.16%per year.The first-year ice increased at the rate of 0.0529×10~6km~2 per year.However,the extent of multi-year ice decreased at the rate of 0.0955×10~6km~2 per year(-23.538%/10 years).(4)Although the general trend of sea ice change in the Antarctic and the Arctic is opposite,the more sensitive sea ice parameter variables,the smaller time scale,and the recent research cycle show more obvious consistency.Sea ice parameter variables:the multi-year ice extent is reduced,and the decrease speed of the Arctic is faster than that of the Antarctic from 1980 to 2018,but the decrease speed of the Antarctic multi-year ice is significantly higher than that of the Arctic from 2014 to 2018;the first-year ice extent is increased,and the increase speed of the Arctic is slightly faster than that of the Antarctic;the melting time of the Antarctic and the Arctic is also consistent with the change trend of the freezing time,among which the melting time of the Antarctic and the Arctic is also consistent,the rate is+0.04 days/year and+0.16days/year respectively,and the change rate of frozen time in Antarctic and Arctic is-0.04 days/year and-0.16 days/year respectively.Small time scale:from 1979 to 2018,the annual minimum monthly average sea ice extent in Antarctica only increased with a weak trend(0.0006×10~6 km~2/year),while the annual minimum daily average sea ice extent in Antarctica and the Arctic decreased with a speed of 0.0002×10~6 km~2/year and 0.0886×10~6 km~2/year respectively.Recent research cycle:in 2009-2018,there was a positive correlation between the overall sea ice extent of the Antarctic and the Arctic,both of which decreased,and the correlation coefficient r*was 0.816,while in2014-2018,the correlation coefficient r*was higher than 0.954.(5)There is a certain relationship between the changes of parameters,and they affect each other.The change of sea ice concentration slightly lags behind the change of the whole sea ice extent.In terms of the relationship between multi-year ice and first-year ice,there is a negative correlation between the Antarctic and the Arctic,with correlation coefficients of-0.34 and-0.79,respectively.And the negative correlation between the mid low and peak years in 1979-2018 is more obvious.The relationship between the whole sea ice extent and the first-year ice and the multi-year ice extent is different between the Antarctic and the Arctic,which is related to the main proportion of sea ice types.The change of the whole sea ice extent in the Arctic is more closely related to the change of the multi-year ice,and the correlation coefficient is as high as 0.83;the relationship between the whole sea ice extent and the first-year ice extent is stronger in the Antarctic,and the correlation coefficient is 0.57. |
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