Feature And Connection Studies Of The Sea Level Trends Of The China Seas And Global Oceans For The Past20Years

The AVISO altimeter products were used to analyze the sea level trend featuresof the China Seas and the Global Oceans from Jan.1993to Jan.2013.Preliminaryanalysis of the impacts of the Global Oceans’ sea level trends on the China Seas arealso given by this study. It is concluded that, to a great extent, the sea level of ChinaSeas is in a passive rise induced by the concurrent global sea level rise. Thepreliminary conclusions of this study are as follows:A: About the China Seas. The mean sea level trend of the China Seas is4.7mm/year, which is higher than the global average. The mean sea level trend of theBohai sea, the Yellow China sea, the East China sea and the South China sea are3.8、3.4、3.3and5.0mm/year, respectively. The mean sea level trend of the areas coveringthe Bohai sea, the Yellow China sea and the East China sea as a whole is3.4mm/year,which is only a little bit higher than the concurrent global average. The mean sea leveltrend of the China Seas’ coastal areas and the whole China Seas are3.7and4.7mm/year respectively, while the mean sea level trend of the China Seas’ boundaryareas reaches as high as4.9mm/year, which is much greater than the whole ChinaSeas and global average. The study concludes that1) the mean sea level trend of theBohai sea, the Yellow China sea, the East China sea and the China Seas’coastal areasare close to the global average, whereas the South China sea contributes considerablyto the sea level rise for the whole China Seas and2) the high sea level trend of theChina Seas’ boundary areas might be the major factor to elevate sea level of the innerareas of the China Seas for the past20years.B: About the Global Oceans. The mean sea level trend of the global Ocean is3.0mm/year. The mean sea level trends of the Pacific Ocean and the Atlantic Oceanare2.6and2.8mm/year respectively, while the mean sea level trend of the IndianOcean reaches4.0mm/year, which is much greater than the other oceans and theglobal average. The standard deviations of the spatial distribution of the sea levels ofthe Global Ocean, the Pacific Ocean, the Indian Ocean and the Atlantic Ocean, whichreflects the non-uniformity of the sea level distribution, are also calculated. Thestandard deviations trends of the Pacific Ocean and the Indian Ocean both are positive, while that of the Atlantic Ocean is negative, suggesting that the spatial sea leveldistributions of the Pacific Ocean and the Indian Ocean have been getting more andmore non-uniform while those of the Atlantic Ocean have been getting more and moreuniform. In order to make a further study of the non-uniformity of the sea leveldistribution, a new index, the volume centroid of the upper ocean layers, is proposedby this study. It is found that the zonal volume centroid of the Pacific Ocean havebeen moving westward at a rate of3.08o/Century, while the zonal centroid of theIndian Ocean and the Atlantic Ocean have been moving eastward at a rate of0.98and0.60o/Century respectively. The meridional volume centroid of all the three majoroceans have been moving southward at different rates. The preliminary conclusionsare:1) Sea level trend distributions of the Global Ocean are in great non-uniformity.The three major oceans are all in rise with different trends, and the Indian Ocean hasthe top trend;2) The trends of the standard deviations of the spatial distribution of thesea level of major oceans show that the spatial sea level distributions of the PacificOcean and the Indian Ocean have been getting more and more non-uniform whilethose of the Atlantic Ocean have been getting more and more uniform. This differencesuggests that the major oceans might have been controlled by different climate system;3) The zonal volume centroid movements of the Pacific Ocean and the Indian Oceanhave opposite directions, showing that the water volumes have been piling up aroundthe Indo-Pacific Warm Pool and its surrounding areas and may bring great risk ofextreme sea level rises to these areas in the future. The meridional volume centroid ofall the three major oceans have been moving southward and the sea level of theSouthern Hemisphere get equal to the Northern Hemisphere.C: About the relation between the Global Oceans and the China Seas.Because the zonal volume centroid movements of the Pacific Ocean and the IndianOcean have the opposite directions, the water volumes have been in a long period oftendency of piling up around the Indo-Pacific Warm Pool, which bears further impactson the sea level distributions of the adjacent areas such as the South China Seas andthe Kuroshio regions. The boundary sea areas of the China Seas consist of parts of theSouth China seas and the Kuroshio currents, both of which have close relation to theWarm Pool areas. The study shows that the tendencies of the zonal volume centroid ofthe Pacific Ocean and the Indian Ocean help elevate the sea levels around the WarmPool areas and the sea level rise of the Warm Pool areas further help elevate the sealevel of the China Seas’ boundaries (especially the South China sea and the Kuroshio regions), which finally results in the passive sea level rise of the China Seas. So, itseems to be also quite necessary to study the sea level trend and the mechanisms ofthe China seas’boundary areas and the Global Oceans.