Coupled Bio-Physical Models for the Coastal Gulf of Alaska

美国GLOBEC东北太平洋实施计划的一个核心假设是，阿拉斯加湾环流和水文地貌的年际至年代际变化驱动沿海地区浮游动物生产力的变化，从而影响墨西哥湾鲑鱼和其他物种的摄食成功。由于物理强迫在空间上的相关变化，阿拉斯加湾沿岸(CGOA)和加利福尼亚州海流的生产体制可能在年际到年代际尺度上有所不同。为了解决CGOA的这些问题，使用了一套相互关联的循环模型，再加上营养水平较低的浮游植物浮游植物(NPZ)生物模型和鲑鱼的基于个体的模型(IBM)。嵌入盆地/全球尺度环流模式的涡流和潮汐分辨CGOA环流模式。这组模型要解决的具体问题包括：1)阿拉斯加近岸流阿拉斯加流(AC AS)和阿拉斯加海岸流(ACC)的相对强度如何影响陆架和斜坡之间的交换，从而影响营养物质和深海浮游动物向陆架地区的供应？2)风驱动的Ekman通量是海洋浮游动物向陆架输送的主要来源，还是更复杂的跨锋过程？3)ACC季节模式的年际/年代际调制如何影响次生生产和向大陆架较高的营养层转移？更强大的ACC是提高还是降低了大陆架上的生产力？4)潮汐混合对阿拉斯加湾的沿海生产有显著影响吗？如果是这样的话，潮汐的极低频率调制是否可以解释海岸动力的一些年代际变化，从而导致生产？所提出的耦合(全球/流域和区域/沿海)环流模式是受现实的风和河流径流时间序列的影响。沿海环流模式的输出将用于推动包括大陆架和大陆架断裂在内的近海地区的NPZ模式。以这种方式产生的循环场和猎物场将被用作幼年鲑鱼的空间显式IBM的输入。这套模型将包括对阿拉斯加湾过去和现有模型的重大改进，后者几乎没有例外地倾向于使用粗略的空间网格或简化的物理模型，其中排除了与生物相关的过程，如沿海地区的斜压不稳定。这项拟议研究的结果将有助于确定阿拉斯加湾内环流、浮游动物和鲑鱼生产的过去和未来趋势和空间模式，并有助于确定陆架坡度交换的机制。模式的输出将提供给东北太平洋GLOBEC的其他PI，作为更精细的区域模式(例如威廉王子湾)的物理和生物边界条件尤其有用。

PROJECT SUMMARY A core hypothesis of the US GLOBEC Northeast Pacific Implementation Plan is that interannual to interdecadal variability in the circulation and hydrography of the Gulf of Alaska drives changes in productivity of zooplankton in the coastal zone, with consequent effects on the feeding success of salmonids and other species in the Gulf. Production regimes in the Coastal Gulf of Alaska (CGOA) and the California Current may covary on interannual to decadal scales, due to spatially correlated changes in physical forcing. To address these issues for the CGOA, a set of linked circulation models, coupled with a lower trophic level Nutrients Phytoplankton Zooplankton (NPZ) biological model, and an individual based model (IBM) of salmon are used. The eddy and tide resolving CGOA circulation model embedded in a basin/global scale circulation model. Specific questions to be addressed by this set of models include: 1) How do the relative strengths of the offshore Alaska Current Alaskan Stream (AC AS) and the Alaska Coastal Current (ACC) affect exchange between the shelf and slope, and hence the supply of nutrients and deep sea zooplankton to the shelf area? 2) Can wind driven Ekman flux account for most of the transport of oceanic zooplankton onto the shelf, or are more intricate cross frontal process involved? 3) How does interannual/decadal modulation of the seasonal pattern of the ACC affect secondary production and transfer to higher trophic levels on the shelf? Does a stronger ACC act to enhance or reduce productivity on the shelf? 4) Does tidal mixing significantly affect coastal production in the Gulf of Alaska? If so, can very low frequency modulation of tides account for some of the decadal change in the coastal dynamics, and hence production? The proposed set of coupled (global/basin and regional/coastal) circulation models are forced by realistic wind and river runoff time series. Output from the coastal circulation model will be used to drive the NPZ model of the near coastal area encompassing the shelf and shelf break. Circulation and prey fields produced in this manner will then be used as input to the spatially explicit IBM of juvenile salmon. This set of models will comprise a significant advance over past and existing models of the Gulf of Alaska, which have with few exceptions tended to use either coarse spatial grids or simplified physics, which exclude biologically relevant processes such as baroclinic instability in the coastal zone. Results of this proposed research will help identify past and future trends and spatial patterns of circulation, zooplankton and salmonid production within the Gulf of Alaska, and help identify mechanisms for shelf slope exchange. Output from the models will be made available to other PI's in Northeast Pacific GLOBEC, and should be especially useful as physical and biological boundary conditions for finer scale regional models (e.g. of Prince William Sound).