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Simulation Of The Vertical Transport Of Particulate Organic Carbon In The Carbon Cycle

Posted on:2013-01-19Degree:MasterType:Thesis
Country:ChinaCandidate:K WangFull Text:PDF
GTID:2230330371484595Subject:Atmospheric physics and atmospheric environment
Abstract/Summary:PDF Full Text Request
As an important component of the ocean carbon cycle, particulate organic carbon (POC) is often used to estimate the primary productivity in the ocean:There are two main aspects in our study. One is through the observation data to analyze the source and transformation of POC and the seasonal and interannual variations of POC vertical fluxes. The other is to study the vertical transport processes of POC with an ocean biogeochemical general circulation model (IAP-OBGCM) developed by the Institute of Atmospheric Physics of the Chinese Academy of Sciences.After the global ocean model LICOM is run, a relatively stable physical field is obtained. According to the temperature and salinity data from WOA09, the simulated basic characteristics of ocean circulation and the major water mass formation are analyzed. On the basis of the steady state of the ocean circulation, as a passive tracer, tritium (3H) is incorporated into the OGCM to study the performance of the model. Simulated results show mat our model well reproduces the observed features of the sea surface distribution, water column inventory, meridional gradient, and local maximum values of tritium. The main shortness of our model is that the penetration depth of simulated tritium is smaller, especially in the two subtropical regions. It is considered that some uncertainties exist in the development of the tritium input function and description of physical processes needs to be improved in the OGCM, which probably influences the simulated results. The lateral ventilation of tritium from the subarctic to tropical regions is obvious along isopyncal surfaces. Our model successfully simulates that tritium enters into the ocean from the high-latitude sea surface, and is transported along isopyncals to the subsurface layer in the low-latitude region, then to the Southern Hemisphere and high-latitude regions by the circulation and diffusion.With the analysis of the observed vertical flux of particulate organic carbon (POC) in the Bermuda area of the North Atlantic, it is found that the vertical flux of POC is controlled by biological activities and that there is a significant positive correlation between the POC flux and the concentration of chlorophyll a, and a weak positive conrrelation between the POC flux and zooplankton activity. The concentration of POC is larger in spring and summer than that in autumn and winter, and this phenomenon is consistent with seasonal variations of chlorophyll a and zooplankton. This reflects that biological production makes an important contribution to the POC flux. According to the vertical distribution characteristic of POC in the ocean, two different POC mineralization profiles are fitted, which include the decay form of exponential function and the combination of exponential and power function with respect to depth, respectively. The comparison between these two new profiles and other power function profiles proposed by other researchers is made. Results indicate that these profiles generate the vertical transport process of POC from the upper Ocean to the bottom to some different extent.Using IAP-OBGCM,, five parameterization schemes are designed in terms of the profile data of the POC in the Bermuda area to study the influences of the production and transformation of POC on the carbon cycle in the ocean interior. Simulated results show that the model successfully reproduces the observed characteristics of dissolved inorganic carbon, total alkalinity, phosphate and so on in the ocean at the preindustrial era. It is known from the simulation results with five parameterization schemes of vertical POC transport that the increase of content in particulate organic carbon can obviously enhance the concentration of DIC below the euphonic zone, but does not have much affect on the redistribution of phosphate.
Keywords/Search Tags:Particulate organic carbon, ocean general circulation model, passive tracer, oceancarbon cycle, biogeochemical process
PDF Full Text Request
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