Climate relevant interactions and feedbacks: the key role of sea ice and snow in the polar and global climate system (CRiceS) EU funded H2020 project

Start date
1 August, 2022
End date
31 August, 2025

Sea ice is an integral, changing part of the global Earth system. The polar climate system affects lives and livelihoods across the world by regulating climate and weather; providing ecosystem services; and regulating the ability of humans to operate (hunting, shipping, and resource extraction). CRiceS improves understanding of how rapid sea ice decline is interlinked with physical and chemical changes in the polar oceans and atmosphere.

In order to plan for and adapt to polar and global climate change, CRiceS aims to fully understand the causes and consequences of this polar transition. Climate and Earth System Models (ESMs) are the key tools for projecting climate change in order to mitigate the impacts and to adapt. However, these models have major shortcomings in their descriptions of interconnected polar ocean-ice/snow-atmosphere interactions that limit their ability to project teleconnections, feedbacks, and impacts. CRiceS will quantify the controlling chemical, biogeochemical, and physical processes/interactions within the coupled ocean-ice/snow-atmosphere system through comprehensive analysis of new and emerging in-situ and satellite observations.

CRiceS improves process, regional, and climate models/ESMs by advancing descriptions of (1) sea ice dynamics/energy exchange, (2) aerosols, clouds and radiation, (3) biogeochemical cycles/greenhouse gas exchanges and (4) fully coupled system behavior. This improved understanding allows for assessment of the role of ocean-ice/snow-atmosphere interactions in polar and global climate and delivers improved quantification of feedback mechanisms and teleconnections within the Earth system. Improved future projections and multi-sectoral impact assessments will increase our capacity to mitigate and adapt to climate and environmental changes in polar regions and beyond. CRiceS brings together 22 leading institutes in Europe and across the globe, including world leading observing and modeling expertise.

External web page:


Lapere, Rémy, Thomas, Jennie L., Marelle, Louis, Ekman, Annica M. L., Frey, Markus M. , Lund, Marianne Tronstad, Makkonen, Risto, Ranjithkumar, Ananth, Salter, Matthew E., Samset, Bjørn Hallvard, Schulz, Michael, Sogacheva, Larisa, Yang, Xin , Zieger, Paul. (2023) The representation of sea salt aerosols and their role in polar climate within CMIP6Journal of Geophysical Research: Atmospheres, 128. 36 pp. 10.1029/2022JD038235


BAS contributes in particular to work packages WP1 and WP2 whose objectives and more detailed description are given below

O1) Translate knowledge across scales from observed OIA processes (e.g. microscopic properties of sea ice, aerosols/clouds, etc.) to controlling climate scale processes within models that describe the coupled ocean-ice/snow-atmosphere system (WP1-2).

We will use state-of-the-art observations to study how the changing polar oceans and sea ice (including its snow cover) control the polar aerosol and cloud lifecycles. We will use Arctic and Antarctic/Southern Ocean data from campaign- based, long-term, and autonomous observing platforms, data infrastructures, and satellite remote-sensing, including emerging data sets, to improve our understanding of processes that govern: ocean and ice emissions that influence primary and secondary aerosols (including from biogeochemical activity); new particle formation; aerosol size distributions; aerosol aging and growth; cloud droplet activation; how aerosols influence cloud abundance and cloud phase and secondary ice production. We focus on processes including seasonal spatio-temporal variability and the direct relationship between sea ice and its snow cover, biogeochemistry, and aerosols/ clouds. The dependence of cloud phase on aerosol properties, atmospheric state parameters, and sea ice will be quantified. The most advanced statistical techniques, new applications of machine learning and data mining techniques will be applied to explore the underlying processes and make recommendations for improved model representations of polar aerosols and clouds.

O2) Advance descriptions of the OIA system in numerical models (WP2) in order to produce more robust projections and to quantify teleconnections, polar – non-polar interactions, feedbacks and impacts (WP3-4).

The latest available data and recommendations from the above task are used to develop novel and improved model descriptions of polar emissions of aerosols and aerosol precursors, aerosol aging, and aerosol-cloud interactions within regional models (WRF-Chem and Enviro-HIRLAM) and global models (UKCA, EC-Earth, and NorESM2). Improved descriptions of polar aerosol and aerosol precursor emissions will be implemented and evaluated for both polar regions. We consider two things (1) sea ice emissions: This includes new and improved descriptions of how emissions depend on sea ice state (lead fraction, age, snow on sea ice) and the occurrence of blowing snow; (2) open ocean emissions: Open ocean polar emissions will be implemented/improved including sea-spray aerosols and aerosol precursors (e.g. iodine and oxidized organics). Further, the processes that determine aerosol growth, and the role of aerosols as cloud condensation nuclei (CCN) and/or ice nuclei (INP) will be refined. To improve the representation of polar cloud formation, current state-of-the-art aerosol activation and heterogeneous freezing parameterizations will be improved. The sensitivity of aerosol-cloud parameterizations to model resolution will be evaluated with specific attention to vertical resolution and the role of capturing the stability of the shallow polar boundary layer on fate and processing of aerosol/ aerosol precursor and cloud formation. Regional models will be used in a downscaling chain to very high resolutions (< 5 km) to test how sea ice heterogeneity (lead fraction, age, and sea ice snow cover including snow salinity) impacts primary aerosol emissions and secondary aerosol formation at cloud resolving model scales. The suite of models will address the role of aerosols and their impact on polar clouds, precipitation, as well as on cloud albedo.