Jahn et al. 2024 posted by Gero above is a very nice paper. It is very readable and provides much-needed clarifications on the various definitions for BOE and ranges of estimates for driving factors and potential date ranges for ASI Area going below 1M km2.
As a backbench armchair amateur, I think the ASI research community is still underestimating the importance of qualitative condition of the ASI and what it means for the timing of BOE. I am referring to the impact of ice thickness, salinity, and pack cohesion / mechanical strength / fracturing. Also, the increasing impact of rain on snow/ice events and potential increase of atmospheric rivers and storm activity in the Arctic Ocean do not seem to get enough attention. Lacking metrics other than some previous posts about accelerating melt as ice thickness gets below 0.8 M, all I have is hunches.
It is interesting to see a similar view for different reasons from people who do know what they are talking about.
https://scitechdaily.com/experts-warn-current-arctic-climate-modeling-too-conservative/ "Two recent scientific studies involving researchers from the University of Gothenburg compared the results of the climate models with actual observations. They concluded that the warming of the Arctic Ocean will proceed at a much faster rate than projected by the climate models."
---------------------------------------------------------
Heuzé, C., H. Zanowski, S. Karam, and M. Muilwijk, 2023: The Deep Arctic Ocean and Fram Strait in CMIP6 Models. J. Climate, 36, 2551–2584,
https://doi.org/10.1175/JCLI-D-22-0194.1.
"Arctic sea ice loss has become a symbol of ongoing climate change, yet climate models still struggle to reproduce it accurately, let alone predict it. A reason for this is the increasingly clear role of the ocean, especially that of the “Atlantic layer,” on sea ice processes. "
"Coupled climate models are routinely used for climate change projection and adaptation, but they are only as good as the data used to create them. And in the deep Arctic, those data are scarce. We determine how biased 14 of the most recent models are regarding the deep Arctic Ocean and the Arctic’s only deep gateway, Fram Strait (between Greenland and Svalbard). These models are very biased: too cold where they should be warm, too warm where they should be cold, not stratified enough, not in contact with the surface as they should, moving the wrong way around the Arctic, etc. Some problems are induced by biases in regions outside of the Arctic and/or from the sea ice models."
"In this study, we first quantified biases in the Atlantic Water in all deep basins of the Arctic. In agreement with Khosravi et al. (2022), we find that its core is too cold by 0.48C on average,
too deep by 400 m, and in half of the models the Atlantic layer extends all the way to the seafloor, i.e., the properties do not evolve with depth as they do in the real ocean. Besides, in most models the properties do not change from basin to basin. We attribute these inaccurate properties and behavior to a lack of shelf overflows in most models found in ocean-only simulations (Ilicak et al. 2016), and inaccurate heat and volume fluxes through Fram Strait."
"At Fram Strait, we found that all models underestimate the volume fluxes in and out of the Arctic, i.e., all models are biased slow"
The Appendix might be of interest to hard core ASIF Arctic Ocean watchers: available on Zenodo (
https://doi.org/10.5281/zenodo.4606856).
APPENDIX
A More Detailed Look at the Model Biases
This appendix presents
• the models’ native grid (Fig. A1);
• the pan-Arctic biases in each water mass in temperature (Fig. A2) and salinity (Fig. A3);
• the models’ polynya activity (Fig. A4);
• the absolute age of the water (Fig. A5);
• the models’ pan-Arctic velocity of the AW core (Fig. A6) and at 2000-m depth (Fig. A7);
and
• the salinity across Fram Strait (Fig. A8).
It also presents the area-weighted mean biases in all basins (Tables A1–A3).
Poll