WAMSI Node 1.1.2 - Coupled hydrodynamic and biogeochemical models

The dynamics of the seasonal evolution of chlorophyll a at the continental shelf break around 32 degrees south has been investigated using a one-dimensional numerical BGC model at shelf and lagoon scales. The results show that a combination of vertical mixing associated with the Leeuwin Current and surface cooling during the winter months is responsible for the wintertime increase in chlorophyll a concentration at the shelf break (Greenwood and Soetaert, 2008). In addition, variation in the timing and magnitude of the winter increase in chlorophyll is shown, for the first time, to relate to the strength of the Leeuwin Current. A nitrogen budget for the southwest WA shelf has been derived by diagnosing the simulated fluxes of particulate and dissolved nitrogen from the 3-D model across the shelf boundaries (across two cross-shelf transects at 27S and 34.5S and across the 100 m isobath) as well as deposition and release of nitrogen at the seafloor.

本研究采用陆架与泻湖尺度的一维数值生物地球化学（BGC）模型，对南纬32度附近大陆架坡折（continental shelf break）处叶绿素a（chlorophyll a）的季节演变动力学特征展开了探究。研究结果显示，冬季月份中与卢因海流（Leeuwin Current）相关的垂直混合与海面冷却共同作用，是该陆架坡折处叶绿素a浓度冬季升高的核心成因（Greenwood和Soetaert，2008）。此外，本研究首次证实，冬季叶绿素浓度升高的发生时机与幅度变化，与卢因海流的强度存在显著关联。通过诊断分析三维（3-D）数值模型模拟得到的跨陆架边界通量，涵盖南纬27度与南纬34.5度的两条跨陆架断面以及跨越100米等深线的区域，同时结合海底的氮沉积与释放过程，本研究构建了西澳大利亚西南部陆架的氮收支体系。