Tag: ottersen

Key physical processes and their model representation for projecting climate impacts on subarctic Atlantic net primary production: A synthesis

Myksvoll, M. S., Sandø, A. B., Tjiputra, J., Samuelsen, A., Çağlar Yumruktepe, V., Li, C., Mousing, E. A., Bettencourt, J.P.H., Ottersen, G. 2023: Key physical processes and their model representation for projecting climate impacts on subarctic atlantic net primary production: A synthesis. Progress in Oceanography. https://doi.org/10.1016/j.pocean.2023.103084

Summary: Oceanic net primary production forms the foundation of marine ecosystems. Understanding the impact of climate change on primary production is therefore critical and we rely on Earth System Models to project future changes. Stemming from their use of different physical dynamics and biogeochemical processes, these models yield a large spread in long-term projections of change on both the global and regional scale. Here we review the key physical processes and biogeochemical parameterizations that influence the estimation of primary production in Earth System Models and synthesize the available projections of productivity in the subarctic regions of the North Atlantic. The key processes and modelling issues we focus on are mixed layer depth dynamics, model resolution and the complexity and parameterization of biogeochemistry. From the model mean of five CMIP6 models, we found a large increase in PP in areas where the sea ice retreats throughout the 21st century. Stronger stratification and declining MLD in the Nordic Seas, caused by sea ice loss and regional freshening, reduce the vertical flux of nutrients into the photic zone. Following the synthesis of the primary production among the CMIP6 models, we recommend a number of measures: constraining model hindcasts through the assimilation of high-quality long-term observational records to improve physical and biogeochemical parameterizations in models, developing better parameterizations for the sub-grid scale processes, enhancing the model resolution, downscaling and multi-model comparison exercises for improved regional projections of primary production.

Link to publication. You are most welcome to contact us or the corresponding author(s) directly, if you have questions.

Latitudinally distinct stocks of Atlantic cod face fundamentally different biophysical challenges under on-going climate change

Kjesbu, O.S., Alix, M., Sandø, A.B., Strand, E., Wright, P.J., Johns, D.G., Thorsen, A., Marshall, C.T., Bakkeplass, K.G., Vikebø, F.B., Myksvoll, M.S., Ottersen, G., Allan, B.J.M., Fossheim, M., Stiansen, J.E., Huse, G., Sundby, S. 2023: Latitudinally distinct stocks of Atlantic cod face fundamentally different biophysical challenges under on-going climate change. Fish and Fisheries. https://doi.org/10.1111/faf.12728

Summary: Observed and future winter Arctic sea ice loss is strongest in the Barents Sea. However, the anthropogenic signal of the sea ice decline is superimposed by pronounced internal variability that represents a large source of uncertainty in future climate projections. A notable manifestation of internal variability is rapid ice change events (RICEs) that greatly exceed the anthropogenic trend. These RICEs are associated with large displacements of the sea ice edge which could potentially have both local and remote impacts on the climate system. In this study we present the first investigation of the frequency and drivers of RICEs in the future Barents Sea, using multi-member ensemble simulations from CMIP5 and CMIP6. A majority of RICEs are triggered by trends in ocean heat transport or surface heat fluxes. Ice loss events are associated with increasing trends in ocean heat transport and decreasing trends in surface heat loss. RICEs are a common feature of the future Barents Sea until the region becomes close to ice-free. As their evolution over time is closely tied to the average sea ice conditions, rapid ice changes in the Barents Sea may serve as a precursor for future changes in adjacent seas.

Link to publication. You are most welcome to contact us or the corresponding author(s) directly, if you have questions.

Skilful prediction of cod stocks in the North and Barents Sea a decade in advance

Koul, V., Sguotti, C., Årthun, M., Brune, S., Düsterhus, Bogstad, B., Ottersen, G., Baehr, J., Schrum, C. 2021: Skilful prediction of cod stocks in the North and Barents Sea a decade in advance. Nature Communications Earth & Environment. https://doi.org/10.1038/s43247-021-00207-6 .

Summary: Reliable information about the future state of the ocean and fish stocks is necessary for informed decision-making by fisheries scientists, managers and the industry. However, regional ocean climate and fish stock predictions for the next few years, and up to 10 years, have until now had low forecast skill. In this article, the authors provide skilful forecasts of the biomass of cod stocks in the North and Barents Seas 10 years in advance. These point to a continuation of unfavorable oceanic conditions for the North Sea cod in the coming years, which would inhibit its recovery at present fishing levels, and a decrease in Northeast Arctic cod stock compared to the recent high levels.

Link to publication. You are most welcome to contact us or the corresponding author(s) directly, if you have questions.