Arctic Ocean Surface Energy Flux and the Cold Halocline in Future Climate Projections

• Main Authors: Metzner, Enrico P., Salzmann, Marc, Gerdes, Rüdiger
• Format: Text
• Language: English
• Published: FID GEO 2020
• Subjects: Arctic; Arctic Ocean; albedo; Sea ice
• Online Access: https://dx.doi.org/10.23689/fidgeo-4564; https://e-docs.geo-leo.de/handle/11858/8910

Ocean heat transport is often thought to play a secondary role for Arctic surface warming in part because warm water which flows northward is prevented from reaching the surface by a cold and stable halocline layer. However, recent observations in various regions indicate that occasionally, warm water is found directly below the surface mixed layer. Here we investigate Arctic Ocean surface energy fluxes and the cold halocline layer in climate model simulations from the Coupled Model Intercomparison Project Phase 5. An ensemble of 15 models shows decreased sea ice formation and increased ocean energy release during fall, winter, and spring for a high-emission future scenario. Along the main pathways for warm water advection, this increased energy release is not locally balanced by increased Arctic Ocean energy uptake in summer. Because during Arctic winter, the ocean mixed layer is mainly heated from below, we analyze changes of the cold halocline layer in the monthly mean Coupled Model Intercomparison Project Phase 5 data. Fresh water acts to stabilize the upper ocean as expected based on previous studies. We find that in spite of this stabilizing effect, periods in which warm water is found directly or almost directly below the mixed layer and which occur mainly in winter and spring become more frequent in high-emission future scenario simulations, especially along the main pathways for warm water advection. This could reduce sea ice formation and surface albedo.