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

Robinson Hordoir from IMR will give this seminar talk on March 14.

Portrett Robinson
Robinson Hordoir

Short biography:

I am a physical oceanographer and ocean modeller. I graduated with an engineering degree in fluid mechanics at Enseeiht, Toulouse, and defended my PhD thesis at the University of Caen, France. I specialize in the modelling of regions of freshwater influence in a changing climate. I am the main developer of the Nemo-Nordic configuration used for operational and research purpose around the Baltic & North Sea basins. I am now developing a similar configuration for Arctic & North Atlantic basins named Nemo-NAA10km. I have been hired as a researcher at IMR in 2018.


Climate change is especially strong in the region of the Arctic Ocean, and will have an important impact on its thermo-haline structure. We analyze the results of a hindcast simulation of a new 3D ocean model of the Arctic and North Atlantic oceans for the period 1970–2019. We compared the time period 1970–1999 with the time period 2010–2019. The comparison showed that there is a decrease of stratification between the two periods over most of the shallow Arctic shelf seas and in the core of the Transpolar Ice Drift. Fresh water inputs to the ocean surface decline, and inputs of momentum to the ocean increase, which can explain the decrease in stratification. The comparison also showed that the mixed layer becomes deeper during winter, in response to the weakened stratification owing to increased vertical mixing. The comparison of summer mixed layer depths between the two time periods follows a deepening pattern that is less evident. Regional exceptions include the Nansen Basin and the part of the Canadian Basin bordering the Canadian Archipelago, where the mixed layer shoals. Trends of freshwater fluxes imply that the changes of haline stratification in these regions are also influenced by other processes, for example, horizontal advection of fresh water, increased mixing and changes in the underlying water masses. Runoff increase toward the Arctic Ocean can locally decrease but also increase salinity, and has an impact on stratification which can be explained by coastal dynamics. The results emphasize the non-linear nature of Arctic Ocean dynamics.

Ref. Paper:

Arranged date for the seminar talk: Mar 14, 2022, Bjerknes lecture room 4020, Jahnebakken 5 at 14:15