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- Title
Understanding the Physical Forcings Behind the Biogeochemical Productivity of the Hudson Bay Complex.
- Authors
Deschepper, Inge; Myers, Paul G.; Lavoie, Diane; Papakyriakou, Tim; Maps, Fréderic
- Abstract
Multiple factors influence the spatial and temporal chlorophyll‐a concentration of marine systems. The Hudson Bay Complex has historically been seen as a large, low‐production inland sea situated in the north of Canada. However, recent field campaigns, for the BaySys project, have provided new data on primary production in the bay. Due to the Hudson Bay complex's positioning, it experiences seasonal sea‐ice cover and has many rivers draining into it, resulting in a unique estuarine‐like environment. We use the biogeochemical model BLINGv0 + DIC, coupled to the online regional physical oceanographic and sea‐ice models, NEMOv3.6 and LIM2, respectively, forced with two bias‐corrected Coupled Model Intercomparison Project 5 climate forcings (MIROC5 and MRI) to simulate the base of the ecosystem. The simulations were evaluated with chlorophyll‐a satellite imagery and observations collected in 2018 and analyzed with Empirical Orthogonal Functions to understand the underlying physical forcings and key areas of chlorophyll‐a concentration distribution. The evaluation showed that both simulations successfully reproduced the sea‐ice melt, from west to east and formation, from north to south and correlated well with spatial bloom patterns. The main drivers of phytoplankton growth are the seasonal light and nutrient levels (48% and 54%), the mixed layer depth dynamics (18% and 14%), nutrient supply from rivers (13% and 8%), and sea ice production (7%) for the MIROC5 and MRI simulations, respectively. The sea‐ice dynamics and river runoff played a significant role in the system's productivity. Therefore, with future climate change and increased river regulation projects, up to 20% of overall chlorophyll‐a may be negatively impacted. Plain Language Summary: The Hudson Bay Complex (HBC) is an inland sub‐Arctic sea that is covered by sea ice from December to June. Many rivers drain into the bay, making it a relatively fresh marine environment. Due to its size, difficulty to access, and seasonal ice cover, it is a challenging environment to sample. A recent Hudson Bay system study, BaySys, has allowed us to understand that the HBC is more productive than previously thought. Using regional numerical ocean, sea ice, and biological models, we can simulate the biological productivity in this area with two different climate forcings. Comparing the simulations with satellite and in situ observations from 2018, we can see that our models simulate sea‐ice production and the spatial and temporal pattern of chlorophyll a relatively well. Using a statistical method called Empirical Orthogonal Functions, we could identify that the physical components influencing this region's phytoplankton growth are the mixed layer depth, river runoff into the area and sea‐ice melt and freeze cycle. The HBC expects to experience significant climate change and changes in river runoff in the future. Any changes in these two physical forcings can negatively impact up to 20% of the overall chlorophyll a distribution patterns. Key Points: Physical and biogeochemical models can be used to understand the underlying drivers of primary productivityThe biogeochemical model, BLINGv0 + DIC, simulates the spatial and temporal distributions of chlorophyll a within the Hudson Bay ComplexMixed layer depth dynamics, river runoff, and sea‐ice production were observed to have the largest impact on simulated chlorophyll a
- Subjects
HUDSON Bay; HUDSON'S Bay Co.; SEA ice; REGULATION of rivers; ORTHOGONAL functions; MIXING height (Atmospheric chemistry); BIOLOGICAL productivity; REMOTE-sensing images
- Publication
Journal of Geophysical Research. Biogeosciences, 2023, Vol 128, Issue 6, p1
- ISSN
2169-8953
- Publication type
Article
- DOI
10.1029/2022JG007294