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

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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