This project will use the Regional Arctic System Model (RASM), comprised of marine biogeochemistry (mBGC) components in the eddy-resolving ocean and sea ice models to advance understanding and prediction of the Arctic biogeochemical system, including shelf-basin and vertical nutrient exchange, the subsurface chlorophyll maximum, ice edge and under ice blooms and their role in ecosystem response to climate change. It builds on the recent and ongoing research by the PIs, including the development and evaluation of mBGC components for global sea ice / ocean models and the highresolution RASM.
There are many physical processes, such as mesoscale eddies, mixed layer dynamics, ocean coastal and boundary currents, upper ocean stratification, varying sea ice cover, marginal ice zone (MIZ) expansion and ice edge upwelling that influence nutrient transport, light availability and ocean stratification, which are critical to marine primary production (PP) and carbon cycling in the Arctic Ocean. Such processes and feedbacks among them might be intimately involved in the recent dramatic changes observed in the Arctic, yet their representation in state-of-the-art global climate and Earth System models (GC/ESMs) is limited due to coarse spatial resolution. Existing data suggest that changes in
biological communities of the Arctic marginal seas are concurrent with shifts in regional atmospheric and hydrographic forcing. We hypothesize that:
1. Nutrients are transported from shelves to the Arctic Basin through narrow currents and eddy transport across the shelf break. The temporal and spatial variation of eddy transport is a critical factor controlling the observed distribution of primary production in the Arctic Basin.
2. Blooms under sea ice cover and along the expanding MIZ are due to enhanced stratification and greater light penetration through ice that is thin and frequently covered by melt ponds. High spatial resolution simulation is critical to resolving such blooms and processes controlling them.
3. In addition, we contend that representation of spatial and temporal patterns of primary production will be improved by high spatial resolution in RASM-mBGC, which will facilitate more accurateestimates of the arctic marine carbon budget.
To address these hypotheses, we will evaluate and synthesize RASM-mBGC results with available ocean, sea ice and biogeochemical data to investigate the significance of high spatial resolution (~5-50 times higher than currently used in global models) in representing critical physical and biological processes controlling Arctic marine primary production and to facilitate the development of strategies to prepare and adapt to consequences of climate change. We will also compare outputs from RASM-mBGC and the Community Earth System Model (CESM), consisting of the same ocean, sea ice, and marine biogeochemistry model components to:
• Quantify the magnitude of biogeochemical inaccuracies in coarse resolution models
• Assess the role of ‘missing’ processes on spatio/temporal biogeochemical property distributions
• Determine the need for explicit representation or upscaling of small-scale arctic processes and feedbacks in GC/ESMs.
This large collaboration between Maslowski (1417888, NPS), Cassano (1417818, CU), Jin (1417925, UAF), and Matrai (1417517, Bigelow) will use the Regional Arctic System Model (RASM), comprised of marine biogeochemistry (mBGC) components in the eddy-resolving ocean and sea ice models to advance understanding and prediction of the Arctic biogeochemical system, including shelf-basin and vertical nutrient exchange, the subsurface chlorophyll maximum, ice edge and under ice blooms and their role in ecosystem response to climate change.
The core work of this project is to carefully evaluate the new RASM-mBGC model using a wide array of physical and biogeochemical observations, no fieldwork is proposed.
