Collaborative Research: Changing Seasonality of the Arctic: Alteration of Production Cycles and Trophic Linkages in Response to Changes in Sea Ice and Upper Ocean Physics

Zhang 0901987华盛顿大学近年来，北极海冰发生了显著的季节性变化，其特征是前所未有的夏季融化，因为夏季融化季节的延长，融化和冻结开始的时间较早。随着夏季海冰范围缩小到创纪录的低水平，北冰洋的外围海洋更早地暴露于大气表面热通量，导致夏季更长，更温暖，海洋吸收更多的热量。北极冰/海洋系统的季节性变化将改变海洋生产周期的时间、规模、持续时间和模式，破坏关键的营养联系和浮游食物网的反馈。这些变化将对北极海洋生态系统的结构产生影响，并影响到整个北极系统，包括人类。因此，了解北极物理和生物系统中季节性模式的变化是很重要的。研究所建议调查北极海冰、水柱、海洋生产周期和营养结构作为一个综合系统之间的季节性联系和相互作用的未来变化。他们的调查将针对以下季节性假设：1）春季海冰退缩时间的变化将导致初级和次级生产时间的不匹配，从而改变浮游生物群落大小结构。这反过来又会改变初级生产的利用率和大型浮游动物猎物的可获得性，以达到较高的营养水平（例如，鲸鱼，鱼类）。2）浮游植物和浮游动物生产周期的紧密耦合将导致春季生产架上水华的规模减少，水柱消费者更多地利用初级生产，并减少其向底栖生物的出口。3）更长的生长季节，其中可能包括夏季晚些时候/初秋的第二次生产高峰，将允许亚北极物种在北冰洋定居，目前由于生长季节持续时间短而无法在那里生存。将通过综合模型估计值以及卫星和实地观测来探讨这些假设。研究人员将利用现有的泛北极生物学/冰/海洋模拟和同化系统（BIOMAS）以及观测，加强他们对海冰、海洋和海洋生产周期综合北极系统的了解。将进行一系列模型后报、敏感性研究和未来情景模拟，以确定季节性敏感联系并检验其假设

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Zhang 0901987University of WashingtonSignificant seasonal changes in arctic sea ice have been observed in recent years, characterized by unprecedented summer melt-back because of the lengthening of the summer melt season with earlier melt and later freeze onsets. As summer sea ice extent shrinks to record low levels, the peripheral seas of the Arctic Ocean are exposed much earlier to atmospheric surface heat flux, resulting in longer and warmer summers with more oceanic heat absorption. The changing seasonality in the arctic ice/ocean system will alter the timing, magnitude, duration, and pattern of marine production cycles, by disrupting key trophic linkages and feedbacks in planktonic food webs. These alterations will have consequences on the structure of arctic marine ecosystems with reverberations through the entire arctic system up to and including humans. It is, thus, important to understand the changes in the patterns of seasonality in the arctic physical and biological system. The PIs propose to investigate future changes in the seasonal linkages and interactions among arctic sea ice, the water column, and the marine production cycles and trophic structure as an integrated system. Their investigation will target the following seasonality hypotheses:1) Changes in the timing of spring sea ice retreat will cause a mismatch in the timing of primary and secondary production such that the plankton community size structure is altered. That in turn will modify the utilization of primary production and the availability of large zooplankton prey for upper trophic levels (e.g., whales, fish).2) Closer coupling of phytoplankton and zooplankton production cycles will result in a reduction in the magnitude of the spring bloom over productive shelves, greater utilization of primary production by water column consumers and a reduction in its export to the benthos.3) A longer growing season, which might include a secondary production peak later in summer/early fall, will permit the colonization of the Arctic Ocean by subarctic species that presently are unable to persist there because of the short duration of the growing season. These hypotheses will be explored by synthesizing model estimates and satellite and field observations. The PIs will use the existing coupled pan-Arctic Biology/Ice/Ocean Modeling and Assimilation System (BIOMAS), together with observations, to strengthen their understanding of the integrated arctic system of sea ice, ocean, and the marine production cycles. A series of model hindcasts, sensitivity studies, and future scenario simulations will be conducted to identify seasonally sensitive linkages and to test their hypotheses