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The representation of sea salt aerosols and their role in polar climate within CMIP6
  • +11
  • Rémy Lapere,
  • Jennie L Thomas,
  • Louis Marelle,
  • Annica M. L. Ekman,
  • Markus Michael Frey,
  • Marianne Tronstad Lund,
  • Risto Makkonen,
  • Ananth Ranjithkumar,
  • Matthew Edward Salter,
  • Bjørn Hallvard Samset,
  • Michael Schulz,
  • Larisa Sogacheva,
  • Xin Yang,
  • Paul Zieger
Rémy Lapere
Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France

Corresponding Author:[email protected]

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Jennie L Thomas
Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
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Louis Marelle
LATMOS/IPSL, Sorbonne Universit ́e, UVSQ, CNRS, Paris, France
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Annica M. L. Ekman
Department of Meteorology, Stockholm University, Stockholm, Sweden
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Markus Michael Frey
Natural Environment Research Council, British Antarctic Survey, Cambridge, UK
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Marianne Tronstad Lund
CICERO Center for International Climate Research, Oslo, Norway
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Risto Makkonen
Finnish Meteorological Institute, Climate Research Programme, Helsinki, Finland
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Ananth Ranjithkumar
Natural Environment Research Council, British Antarctic Survey, Cambridge, UK
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Matthew Edward Salter
Department of Meteorology, Stockholm University, Stockholm, Sweden
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Bjørn Hallvard Samset
CICERO Center for International Climate Research, Oslo, Norway
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Michael Schulz
Norwegian Meteorological Institute, Oslo, Norway
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Larisa Sogacheva
Finnish Meteorological Institute, Climate Research Programme, Helsinki, Finland
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Xin Yang
Natural Environment Research Council, British Antarctic Survey, Cambridge, UK
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Paul Zieger
Department of Meteorology, Stockholm University, Stockholm, Sweden
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Abstract

Natural aerosols and their interactions with clouds remain an important uncertainty within climate models, especially at the poles. Here, we study the behavior of sea salt aerosols (SSaer) in the Arctic and Antarctic within 12 climate models from CMIP6. We investigate the driving factors that control SSaer abundances and show large differences based on the choice of the source function, and the representation of aerosol processes in the atmosphere. Close to the poles, the CMIP6 models do not match observed seasonal cycles of surface concentrations, likely due to the absence of wintertime SSaer sources such as blowing snow. Further away from the poles, simulated concentrations have the correct seasonality, but have a positive mean bias of up to one order of magnitude. SSaer optical depth is derived from the MODIS data and compared to modeled values, revealing good agreement, except for winter months. Better agreement for AOD than surface concentration may indicate a need for improving the vertical distribution, the size distribution and/or hygroscopicity of modeled polar SSaer. Source functions used in CMIP6 emit very different numbers of small SSaer, potentially exacerbating cloud-aerosol interaction uncertainties in these remote regions. For future climate scenarios SSP126 and SSP585, we show that SSaer concentrations increase at both poles at the end of the 21st century, with more than two times mid-20th century values in the Arctic. The pre-industrial climate CMIP6 experiments suggest there is a large uncertainty in the polar radiative budget due to SSaer.