Arctic Ocean Surface Energy Flux and the Cold 2 Halocline in Future Climate Projections

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Metzner, enrico, Salzmann, marc, Gerdes, Rüdiger
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: american geophysical union 2020
• Subjects: albedo; Arctic; Arctic Ocean; Sea ice
• Online Access: https://epic.awi.de/id/eprint/50991/; https://hdl.handle.net/10013/epic.7d794c47-a8cd-4175-bc4c-94c55958373f

Ocean heat transport is often thought to play a secondary role for Arctic surface warm16 ing in part because warm water which ows northward is prevented from reaching the 17 surface by a cold and stable halocline layer. However, recent observations in various re18 gions indicate that occasionally, warm water is found directly below the surface mixed 19 layer. Here we investigate Arctic Ocean surface energy uxes and the cold halocline layer 20 in climate model simulations from the Coupled Model Intercomparison Project Phase 21 5 (CMIP5). An ensemble of 15 models shows decreased sea ice formation and increased 22 ocean energy release during fall, winter, and spring for a high-emission future scenario. 23 Along the main pathways for warm water advection, this increased energy release is not 24 locally balanced by increased Arctic Ocean energy uptake in summer. Because during 25 Arctic winter, the ocean mixed layer is mainly heated from below, we analyze changes 26 of the cold halocline layer in the monthly mean CMIP5 data. Fresh water acts to sta27 bilize the upper ocean as expected based on previous studies. We �nd that in spite of 28 this stabilizing e�ect, periods in which warm water is found directly or almost directly 29 below the mixed layer and which occur mainly in winter and spring become more fre30 quent in high-emission future scenario simulations, especially along the main pathways 31 for warm water advection. This could reduce sea ice formation and surface albedo. 32 Plain Language