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.

本研究采用适用于陆架与泻湖尺度的一维数值生物地球化学（Biogeochemical, BGC）模型，对南纬32°附近大陆架坡折处叶绿素a的季节演化动力学特征展开了探究。结果表明，冬季月份与勒温海流（Leeuwin Current）相关的垂直混合过程及海面冷却共同作用，导致陆架坡折处叶绿素a浓度在冬季出现升高（Greenwood与Soetaert，2008）。此外，本研究首次揭示：冬季叶绿素浓度升高的出现时机与幅值变化，与勒温海流的强度密切相关。本研究还通过诊断三维模型模拟得到的、跨陆架边界（覆盖南纬27°与34.5°的两条跨陆架断面以及100米等深线）的颗粒态与溶解态氮通量，结合海底氮的沉积与释放过程，构建了西澳大利亚西南部陆架的氮收支模型。