Tag: hordoir

A multi-scenario analysis of climate impacts on plankton and fish stocks in northern seas

Sandø, A.B., Hjøllo, S.S., Hansen, C., Skogen, M.D., Hordoir, R., Sundby,S. 2024: A multi-scenario analysis of climate impacts on plankton and fish stocks in northern seas. https://doi.org/10.1111/faf.12834

Summary: Globally, impacts of climate change display an increasingly negative development of marine biomass, but there is large regional variability. In this analysis of future climate change on stock productivity proxies for the North Sea, the Norwegian Sea, and the Barents Sea, we have provided calculations of accumulated directional effects as a function of climate exposure and sensitivity attributes. Based on modelled changes in physical and biogeochemical variables from three scenarios and knowledge of 13 different stocks’ habitats and response to climate variations, climate exposures have been weighted, and corresponding directions these have on the stocks have been decided. SSP1-2.6 gives mostly a weak cooling in all regions with almost negligible impacts on all stocks. SSP2-4.5 and SSP5-8.5 both provide warmer conditions in the long term but are significantly different in the last 30 years of the century when the SSP5-8.5 warming is much stronger. The results show that it is the current stocks of cod and Calanus finmarchicusin the North Sea, and polar cod and capelin in the Barents Sea that will be most negatively affected by strong warming. Stocks that can migrate north into the northern seas such as hake in the Norwegian Sea, or stocks that are near the middle of the preferred temperature range such as mackerel and herring in the Norwegian Sea and cod and Calanus finmarchicus in the Barents Sea, are the winners in a warmer climate. The highly different impacts between the three scenarios show that multiple scenario studies of this kind matter.

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Changes in Arctic Stratification and Mixed Layer Depth Cycle: A Modeling Analysis

Hordoir, R., Skagseth, Ø., Ingvaldsen, R.B., Sandø, A.B., Löptien, U., Dietze, H., Gierisch, A.M.U., Assmann K.A., Lundesgaard,Ø., Lind, S. 2022: Changes in Arctic Stratification and Mixed Layer Depth Cycle: A Modeling Analysis. JGR Oceans. https://doi.org/10.1029/2021JC017270

Summary: We analyzed the results of an ocean model simulation for the Arctic and North Atlantic oceans for the period 1970–2019. Our model is in line with the recent observed changes in the Arctic Ocean and allows, in contrast to the rather sparse observations, a detailed assessment of stratification changes. These changes will affect the Arctic ecosystem and are also believed to affect the large scale ocean circulation. We show that major changes in upper ocean conditions are caused by changes in the fresh water supply by sea ice and varying effect of the wind on regions that are now becoming ice-free. We also study the effect of changes in river runoff into the Arctic Ocean. Our study shows that an increase in river runoff can change the coastal circulation and results, paradoxically, in regions of higher salinity. These results point to the importance of modeling tools when it comes to a better understanding of ocean processes in a changing climate.

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