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The Arctic Ocean in CMIP6 models: Biases and projected changes in temperature and salinity
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  • Narges Khosravi,
  • Qiang Wang,
  • Nikolay V. Koldunov,
  • Claudia Hinrichs,
  • Tido Semmler,
  • S. Danilov,
  • Thomas Jung
Narges Khosravi
Alfred Wegener Institute for Polar and Marine Research

Corresponding Author:[email protected]

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Qiang Wang
Alfred Wegener Institute for Polar and Marine Research
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Nikolay V. Koldunov
Alfred Wegener Institute for Polar and Marine Research
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Claudia Hinrichs
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
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Tido Semmler
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
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S. Danilov
Alfred Wegener Institute for Polar and Marine Research
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Thomas Jung
AWI
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Abstract

We examine the historical evolution and projected changes in the hydrography of the deep basin of the Arctic Ocean in 23 climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The comparison between historical simulations and an observational climatology shows that the simulated Atlantic Water (AW) layer is too deep and thick in the majority of models, including the multi-model mean (MMM). Moreover, the halocline is too fresh in the MMM. Overall our findings indicate that there is no obvious improvement in the representation of the Arctic hydrography in CMIP6 compared to CMIP5. The climate change projections reveal that the sub-Arctic seas are outstanding warming hotspots, causing a strong warming trend in the Arctic AW layer. The MMM temperature increase averaged over the upper 700 m at the end of the 21st century is about 40\% and 60\% higher in the Arctic Ocean than the global mean in the SSP245 and SSP585 scenarios, respectively. Salinity in the upper few hundred meters is projected to decrease in the Arctic deep basin in the MMM. However, the spread in projected salinity changes is rather large and the tendency toward stronger upper 400 m ocean stratification in the MMM is not simulated by all the models. The identified biases and projection uncertainties call for a concerted effort for major improvements of coupled climate models.
Feb 2022Published in Earth's Future volume 10 issue 2. 10.1029/2021EF002282