Changes in coastal oceanography over decades and longer: Combining dynamics and downscaling

点击翻译按钮获取中文摘要

The world's coastal oceans are small compared to the open ocean but they contribute 50% of ocean biological productivity, are the regions most influenced by humans and the regions most used by humans. As with the open ocean, our coastal oceans are experiencing rapid change due to human influences including climate change and contamination. They are becoming warmer, more acidic and less oxygenated. A lot of coastal oceanography research has focused on shorter time scales: days to years. However many of the most significant questions have longer time scales. Questions such as: A) Has carbon input since pre-industrial times significantly changed the pH? Many shellfish make their shells from calcium carbonate minerals that are harder to produce and maintain as pH decreases. Thus a related, and more direct question for impacts is, has carbon input significantly changed the energy required to produce these structures? What changes are expected in the next decades? B) Have there been changes of primary productivity over the last century as suggested by the long term changes in fish production?  We have good records of fishing success but historical records of the phytoplankton and zooplankton are sparse.  Past levels need to be reconstructed to answer this question. C) How will our tides change as sea-level increases?  As sea-level rises the shape of our coastal regions, particularly narrow straits and deltas, change.  These changes will change the tides and thus can act to increase or decrease the impact of sea-level rise on flooding. D) How much will oxygen change in our coastal waters as climate changes? Decreases in oxygen in the open ocean and increased nutrient pollution from the land will both tend to decrease coastal oxygen but strong levels of mixing will tend to moderate that increase.  Changes in primary productivity may also have synergistic and significant effects. In this proposal, we will use information from the past and projections of the future from climate models, downscaled to the coastal region to attack these questions.  Coastal regions are complex. We will focus on the Salish Sea which contains a diversity of coastal regimes. We will use SalishSeaCast a high resolution numerical model that includes circulation, nutrients, oxygen, carbon, phytoplankton and zooplankton. Rather than "broad-brush" past reconstructions and future projections we will concentrate on the specific processes that determine the answers to each of our questions to ensure accuracy and improve understanding.  This targeted downscaling process is a new technique for this research field. In the short term, our goals are answers to the first two questions. Both answers will aid Canada in fisheries policy (shellfish aquaculture and wild and farmed salmon fisheries, respectively) by better defining what has caused the observed changes in the past and by projecting the changes we can expect to see in the future.