海洋生物地球化学模式研究进展

海洋生物地球化学模式是定量认识物质的海洋生物地球化学循环、理解其控制机制以及预测体系变动的重要手段。20世纪90年代以来,该研究领域的进展主要体现在海洋生物地球化学循环的物理输送和生态动力学过程以及年际、年代际变动的模拟3个方面。物理过程模拟方面的进展,集中在寡营养海区上层海水营养盐的供应机制问题上,在经典的上升流、垂直扩散之外,提出涡旋可能构成一种重要的物理输入过程。而生态动力学过程的模拟方面,90年代前期考虑食物网基本结构,由浮游植物、浮游动物和细菌三大类群构成生物状态变量,氮和磷营养盐以及颗粒碎屑构成其他状态变量;90年代后期,开始引入铁和硅的限制问题,考虑不同浮游植物和浮游动物群落结构的影响,特别是浮游植物粒级结构变化的预测可能是未来该领域力图解决的一个技术问题。年际变化的模拟,多围绕ENSO事件对初级生产的影响及其机制问题展开;年代际和地质年代尺度的体系变动问题仍存在争论,相对缺乏有效的数值模拟研究。该研究领域未来应加强生物—化学过程的函数表达、物理模式、中尺度过程、边界交换以及资料获取技术等方面的研究,以应对目前面临的诸多问题与挑战。

AN OVERVIEW OF MARINE BIOGEOCHEMICAL MODELING

The recent development and progress in marine biogoechemical modeling are reviewed and summarized. In general, biogeochemical models can be classified into several different categories according to various physical, biological and chemical processes in the oceans. There are three main types of modeling approaches focusing on physical transport of nutrients, ecosystem dynamics, and temporal variability of biogeochemical processes in the oceans.Ocean current and mixing are dominate processes in supplying nutrients to the euphotic zone. In the upwelling regions, the vertical advection through upwelling is the main mechanism to deliver nutrients. In the central gyre regions, vertical mixing had been thought as a key process to bring nutrients to the surface. Recent field observations and modeling work have suggested that the vertical motion (both upwelling and downwelling) associated with meso-scale eddy activities in the gyre regions can be a potentially important to supply nutrients into the euphotic zone. So far, most models developed for the central gyre regions are one-dimensional or coarse resolution three-dimensional, and more eddy-resolving biogeochemical models are needed.Prior to early 1990's, most ecosystem models were developed following a general nutrient-phytoplankton-zooplankton-detritus (NPDZ) structure. The state variables are single phytoplankton and zooplankton specie, nitrate or phosphate as a limiting nutrient, and a sinking detritus pool. Recently, development of ecosystem model has been advanced with considering multiple limiting nutrients such as iron and silicate, incorporating more phytoplankton and zooplankton functional groups, and separating detritus materials with different sinking velocity. These advances in ecosystem modeling allow us to investigate more complex processes in the oceans, such as nitrogen fixation by cyanobacterium, iron fertilization, and role of remineralization in nutrient and carbon cycle.The ecosystem and biogeochemical processes in responses to climate variability have been main interests in developing and testing models. Prior to 1990's, most models were focused on reproducing and understanding seasonal cycle and nutrients and phytoplankton dynamics. Recently, lots of progresses have been made in terms of modeling and understanding on how ecosystem dynamics respond to climate variability on longer time scale, such as El Nino and Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO).The progresses in biogeochemical modeling have been made rapidly during the past decade, but challenges are still ahead. For example: physical circulation models need to consider meso-scale processes and to resolve eddy-induced nutrient transports; phytoplankton and zooplankton functional groups need to be better incorporated into models based upon both field and laboratory experiments; biogeochemical models need to be linked from global to basin and regional scales, and property exchange at boundaries across these three scales needs more attention; data assimilation technique is also needed to refine parameter values in ecosystem models. In order to build and establish predictive capabilities of biogeochemical models, multi-disciplinary observational networks and computing facilities should be developed and supported.