Impact of River Chemistry on Arctic Coastal Production
Using an Earth System Model we explored the impact of timing and river nutrient concentrations on primary production in each coastal Arctic region and then assessed how this influenced secondary production and particle fluxes supporting the benthic food web. Our results indicate that while the concentration of Arctic river nitrogen can have a significant impact on annual average nitrogen and primary production in the coastal Arctic, with production increases of up to 20% in the river-influenced interior Seas, the timing of the river nutrient inputs into the marine environment appears less important. Additionally, we applied established empirical relationships to the model output to illustrate the important role dissolved organic carbon could play in modulating production - this is a process currently not captured in the model.
In some of the interior Arctic seas, a doubling of river nutrients increased production by the same amount as a projected temperature increase. This highlights the importance of representing the nutrient concentrations and nutrient fluxes to the Arctic as precisely as possible. We have also illustrated that, via light attenuation, dissolved organic carbon from Arctic rivers could impact light attenuation in the water column as much as the Chl-a in phytoplankton. Due to its potential impact on light and heat penetration through the water column this bio-physical link, which is currently not in the model, needs to be explored further. Our findings highlight the importance of developing more realistic river nutrient and discharge forcing for Earth System Models such that their impact on the critical Arctic coastal domain can be more adequately resolved.
Using the Energy Exascale Earth System Model we explore the impact of timing and river nutrient concentrations on primary production in each coastal Arctic region and then assess how this influences secondary production and particle fluxes supporting the benthic food web. Our results indicate that while the concentration of Arctic river nitrogen can have a significant impact on annual average nitrogen and primary production in the coastal Arctic, with production increases of up to 20% in the river-influenced interior Seas, the timing of the river nutrient inputs into the marine environment appears less important. Bloom timing and partitioning between small and large phytoplankton were minimally impacted by both river nutrient concentration and timing, suggesting that in general, the coastal Arctic ecosystem will continue to be primarily driven by light availability, rather than nutrients. With increased river nutrients, the particulate organic flux to the benthos could increase more than the primary production, suggesting changes to the Arctic food web structure and dynamics.