| Global warming has been a heated topic for decades. The causes responsible forthis are diversity, whereas the main reasons can be divided into natural factors andanthropogenic ones. Specifically, they include the repeated cycles of ice ages andwarm ages on global scale and the release of large amount of warm gas. Globalwarming can exert significant influences on human society in many aspects.Environmentally, global warming can lead to temperature rise on earth’s surface. Thenthe ice might resolve and the sea level rises, resulting in disastrous consequences forthe inhabitance. Economically, although global warming has potential to increase theamount of crops, the unpredictable extreme climate events derived from globalchange can adversely affect the growth of crops significantly. Plus, global change canboost the spread of infectious diseases, causing society instability.Climatologists and oceanographers have done a great deal of work with respectto global warming. The relationships between global warming and sea surfacetemperature, sea level pressure, sea ice, etc. have been studied thoroughly andnumerous signals and effects of global warming have been identified. Constrainedwith data resource, however, most of current works focus on sea surface and the air.Researches into deep oceans are scarce. While after commencing the21stcentury, therealization of Argo project has made it possible to observe the deep oceans’temperature and salinity. Moreover, in2009, the first satellite to measure SoilMoisture and Ocean Salinity (SMOS) has been successfully launched by EuropeanSpace Agency (ESA), realizing the measuring of sea surface salinity from space forthe first time in history. Under all these favorable conditions, taking advantage ofSMOS data set and Argo data, we investigate into the vertical changes of seatemperature and sea salinity modes. Main works done are as follows.1. Before simply utilizing any SMOS Level3(L3) data set, we decide to take acomprehensive comparison between two SMOS L3data sets: one provided from CATDS, France and the other from Barcelona Expert Center (BEC), Spain, bothagainst Argo upper measurements. As SMOS satellite has been launched for just ashort time, the quality assessment, calibration and improvement of the data areessential. Our results show that the quality of CATDS Version2data set is better, thusleading us to choose this data set in the following studies.2. Combined with auxiliary long time series in-situ measurements, we use SMOSand Argo data to take a deep research into the vertical changes of sea temperature andsalinity from surface to2000m depth, ranging from global scale to regional scale. As aresult, a strong signal of temperature and salinity increase in some regions (like innorth Atlantic and tropical Indian-Pacific Ocean) in1000-2000m depth is observedfor the past decade. However, this signal is not so obvious on sea surface. Thiscouples with the assumption of the transfer of global warming from earth’s surface tothe deep oceans, which needs further studies.3. Study of Annual Amphidromic Columns of Sea Temperature (AACST). Forthe first time, the concept of “amphidromic column” has been defined, referring to thecolumn that an amphidromic point extends for a given depth at the same location.Four AACSTs have been successfully identified in this study across global oceans.Given that it is coupled with the lower limit of the oceanic mixed layer and provides adirect measure of the solar penetration, the determination of AACST has manypotential implications ranging from a more precise monitoring of the interannual tomulti-decadal temperature changes under global warming, to a better understanding ofthe thermal-dynamical, and fishery processes in the tropical oceans.Thanks to the high quality data sets and maturely developed methods, the robustof the result is considerably high. The knowledge of global warming will be enrichedaccordingly. However, since the time spans of the data sets are relatively narrow, theexploration of long term characteristics and trends of global warming is largelyrestricted. Hence, the work in this thesis is a worthwhile topic in the long term. |
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