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Abstract We provide an assessment of the current and future states of Arctic sea ice simulated by the Community Earth System Model version 2 (CESM2). The CESM2 is the version of the CESM contributed to the sixth phase of the Coupled Model Intercomparison Project (CMIP6). We analyze changes in Arctic sea ice cover in two CESM2 configurations with differing atmospheric components: the CESM2(CAM6) and the CESM2(WACCM6). Over the historical period, the CESM2(CAM6) winter ice thickness distribution is biased thin, which leads to lower summer ice area compared to CESM2(WACCM6) and observations. In both CESM2 configurations, the timing of first ice‐free conditions is insensitive to the choice of CMIP6 future emissions scenario. In fact, the probability of an ice‐free Arctic summer remains low only if global warming stays below 1.5°C, which none of the CMIP6 scenarios achieve. By the end of the 21st century, the CESM2 simulates less ocean heat loss during the fall months compared to its previous version, delaying sea ice formation and leading to ice‐free conditions for up to 8 months under the high emissions scenario. As a result, both CESM2 configurations exhibit an accelerated decline in winter and spring ice area, a behavior that had not been previously seen in CESM simulations. Differences in climate sensitivity and higher levels of atmospheric CO2by 2100 in the CMIP6 high emissions scenario compared to its CMIP5 analog could explain why this winter ice loss was not previously simulated by the CESM.
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Simulated increases of future Arctic dimethylsulfide ocean concentrations, emissions and high-flux events
Simulations from a regional ocean and sea ice model are presented to analyze the potential impacts of climate change on dimethylsulfide (DMS) ocean concentrations and emissions in the Arctic Ocean during the 21st century for a scenario of strong warming (RCP8.5, 2016–2085). The model used includes sulfur biogeochemistry in both the ocean and sea ice, representing the production of dimethylsulfoniopropionate and its conversion to DMS. Simulated DMS concentrations and emissions increase overall in the future throughout the Arctic. Substantial increases of summer ocean surface DMS concentrations and emissions are projected in the shallow continental shelves of the Eastern Arctic, due to a large reduction of sea ice cover. In the Central and Western Arctic, moderate increases of spring DMS production are trapped below sea ice even in the late 21st century. In deep basins, despite ice-free summers in the future, simulated DMS emissions are low, as DMS production occurs mostly below the mixed layer and remains at depth. The strong temporal variability of near-surface winds results in bursts of DMS emissions lasting a few days, with sea-to-air fluxes up to 10 times higher than the monthly median emissions rate. These spikes of DMS emissions occur throughout the Arctic, indicating an episodic impact of DMS on climate in areas of low mean DMS emissions. The simulated frequency of high-flux events increases during the 21st century in both spring and summer in almost all regions of the Arctic. However, the model is not capable of representing rapid out-gassing events during sea ice break-up, and improvements in the representation of leads are still necessary to fully assess the role of sea ice DMS production. With the ongoing decrease in anthropogenic sulfur emissions, these results suggest a future amplification of the role of DMS in aerosol and cloud formation in the Arctic.
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- Award ID(s):
- 2140395
- PAR ID:
- 10648532
- Publisher / Repository:
- University of California Press
- Date Published:
- Journal Name:
- Elem Sci Anth
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2325-1026
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1525/elementa.2024.00090
