Modeling the ecological and biogeochemical changes of the Arctic Ocean caused by the recent decline of sea-ice

One of the most visible effects of Arctic Ocean (AO) warming is the drastic loss of sea-ice cover over the last four decades, including two extreme sea-ice loss events during September 2007 and 2012. The process of formation and melting of sea-ice in the AO modulates the seasonal cycle of phytoplankton growth, primary production, and pelagic and benthic food web dynamics. Satellite-based studies have revealed that recent changes in Arctic climate are causing both earlier break-up and delayed formation of Arctic sea-ice resulting in: 1) earlier phytoplankton bloom initiation, 2) a second, unprecedented fall bloom, and 3) a northward migration of blooms. Documented changes in the physical-chemical properties of Arctic waters have also triggered ecological shifts, such as coccolithophore migration into the Barents Sea and a shift from large-to-small phytoplankton types in the Western AO. Using the data-assimilative ECCO-Darwin (ED) global ocean biogeochemistry model, we investigate how these spatio-temporal modifications to the seasonal bloom and ecological shifts can affect deep carbon export and ultimately the strength of the AO biological carbon pump. ED is an ideal modeling framework for this work, as it includes both a sea-ice component and an ecosystem model with five phytoplankton and two zooplankton groups, which are coupled to ocean carbon chemistry variables. We focus on the 1996–2018 period in an effort to shed light on the relationship between phytoplankton bloom dynamics, ecological shifts, and changes in ocean carbon export. We then test the ED solution against available data to verify its ability to resolve documented ecological and biogeochemical changes in the AO.