Relative Impact of Sea Ice and Temperature Changes on Arctic Marine Production

• Published in: Journal of geophysical research. Biogeosciences 2020-07, Vol.125 (7), p.n/a
• Main Authors: Gibson, Georgina, Weijer, Wilbert, Jeffery, Nicole, Wang, Shanlin
• Format: Article
• Language: English
• Subjects: Air; Air temperature; Algae; Arctic; Atmospheric models; Carbon; Carbon cycle; Carbon dioxide; Carbon fixation; Carbon sinks; Climate; Climate system; Computer simulation; Dynamics; Earth; Ecosystem assessment; Ecosystem dynamics; Environmental changes; Environmental impact; ENVIRONMENTAL SCIENCES; Experiments; Fluctuations; Flux; Global climate; Ice cover; Ice volume; Marine ecosystems; Net Primary Productivity; Ocean temperature; Ocean warming; Phytoplankton; Primary production; production; Sea ice; warming; Water circulation; Water column; Water temperature
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2019JG005343

We use a modern Earth system model to approximate the relative importance of ice versus temperature on Arctic marine ecosystem dynamics. We show that while the model adequately simulates ice volume, water temperature, air‐sea CO2 flux, and annual primary production in the Arctic, itunderestimates upper water column nitrate across the region. This nitrate bias is likely responsible for the apparent underestimation of ice algae production. Despite this shortcoming, the model appears to be a useful tool for exploring the impacts of environmental change on phytoplankton production and carbon dynamics over the Arctic Ocean. Our experiments indicate that under a warmer climate scenario, the percentage of ocean warming that could be apportioned to a reduction in ice area ranged from 11% to 100%, while decreasing ice area could account for 22–100% of the increase in annual ocean primary production. The change to CO2 air‐sea flux in response to ice and temperature changes averaged an Arctic‐wide 5.5 Tg C yr−1 (3.5%) increase, into the ocean. This increased carbon sink may be short‐lived, as ice cover continues to decrease and the ocean warms. The change in carbon fixation from phytoplankton in response to increased temperatures and reduced ice was generally more than a magnitude larger than the changes to CO2 flux, highlighting the importance of fully considering changes to the marine ecosystem when assessing Arctic carbon cycle dynamics. Our work demonstrates the importance of ice dynamics in controlling ocean warming and production and thus the need for well‐behaved ice and BGC models within Earth system models if we hope to accurately predict Arctic changes. Plain Language Summary Through their impacts on water temperature and sea ice cover, changes to the global climate system are likely to have large implications for Arctic marine ecosystems and consequently for Arctic marine production and the carbon cycle. Here we performed a series of experiments with a modern Earth system model to determine the relative importance of ice and temperature for annual net primary production and air‐sea CO2 flux across the Arctic Ocean. We compared model estimates from a validated baseline run to estimates from a model that had been driven with a warmer atmosphere and to projections from a model that had artificially reduced sea ice. Our experiments indicate that as the climate warms, the loss of ice cover will have a larger impact on ocean temperature and primary production th