Arctic Ocean simulations in the CMIP6 Ocean Model Intercomparison Project (OMIP)

Abstract

Abstract. Arctic Ocean simulations in 19 global ocean–sea-ice models participating in the Ocean Model Intercomparison Project (OMIP) of the Coupled Model Intercomparison Project Phase 6 (CMIP6) are evaluated in this paper. Our findings show no significant improvements in Arctic Ocean simulations from the previous Coordinated Ocean-ice Reference Experiments phase II (CORE-II) to the current OMIP. Large model biases and inter-model spread exist in the simulated mean state of the halocline and Atlantic Water layer in the OMIP models. Most of the OMIP models suffer from a too thick and deep Atlantic Water layer, a too deep halocline base, and large fresh biases in the halocline. The OMIP models qualitatively agree on the variability and change of the Arctic Ocean freshwater content; sea surface height; stratification; and volume, heat, and freshwater transports through the Arctic Ocean gateways. They can reproduce the changes in the gateway transports observed in the early 21st century, with the exception of the Bering Strait. We also found that the OMIP models employing the NEMO ocean model simulate relatively larger volume and heat transports through the Barents Sea Opening. Overall, the performance of the Arctic Ocean simulations is similar between the CORE2-forced OMIP-1 and JRA55-do-forced OMIP-2 experiments.

A Review of Arctic–Subarctic Ocean Linkages: Past Changes, Mechanisms, and Future Projections

“…The simulations driven by the CORE2 atmospheric forcing [122] belong to OMIP1 with a simulation period of 1948-2009, and those driven by the JRA55-do atmospheric forcing [123] belong to OMIP2 with a simulation period of 1958-2018. The Arctic Ocean simulations in OMIP was evaluated in [124] and we make use of their analyzed multi-model-mean ocean transports. OMIP models can relatively well represent observed variability in Arctic Ocean hydrography and gateway transports, but the simulated mean ocean state displays considerable bias [124], similar to the findings in the previous CORE-II project [125].…”

Arctic freshwater impact on the Atlantic Meridional Overturning Circulation: status and prospects

“…These state estimates are our best (albeit imperfect and provisional) tools to track and understand the basin-scale, decadal stratification and circulation changes. Study and refine coupled climate models to resolve Arctic Ocean biases, especially in the Atlantic Water, the halocline and the surface Polar Water layer, and thereby decrease the model spread in projected salinity changes [ 24 , 27 ]. Perform consistent, robust budget analyses (like those in figures 2 , 5 and 6 ).…”

“…Study and refine coupled climate models to resolve Arctic Ocean biases, especially in the Atlantic Water, the halocline and the surface Polar Water layer, and thereby decrease the model spread in projected salinity changes [ 24 , 27 ].…”

“…The projected increase in atmospheric moisture flux convergence is moderately well established [20][21][22][23], but the anticipated changes to the marine outflows are poorly known. Moreover, well-known, stubborn biases exist in the Arctic Oceans of CMIP6 models [11,[24][25][26][27].…”

The Arctic Ocean’s Changing Beaufort Gyre System: An Assessment of Current Understanding, Open Questions and Future Research Directions

“…Progress has also been made on understanding change with the Estimating the Circulation and Climate of the Ocean state estimate, a data-constrained reconstruction of the evolving ocean and sea ice state (Fukumori et al 2021). Of particular relevance to modeling the Beaufort Gyre system, Arctic Ocean simulations in Coupled Model Intercomparison Project (CMIP6) models indicate large biases in halocline structure and transport through Bering Strait (Shu et al 2023); ongoing analyses are exploring this in context with new understanding of the physical drivers of the Pacific-Arctic connection.…”