Potential Link Between Ice Nucleation and Climate Model Spread in Arctic Amplification

Abstract

Ice-nucleating particles (INPs) facilitate the formation of ice crystals in clouds by lowering the energy barrier for heterogeneous ice nucleation relative to homogeneous ice nucleation (Rogers & Yau, 1989). Ice crystals commonly coexist with supercooled liquid droplets in mixed-phase clouds at temperatures between 0 and ∼−38°C (Korolev et al., 2017). These clouds are radiatively important, particularly in the Arctic (poleward of 60°N), where they are ubiquitous in the boundary layer (Mioche et al., 2017). Despite their inherent thermodynamic instability, observations have revealed that Arctic mixed-phase clouds are persistent as a result of interactions between microphysical processes such as ice nucleation, as well as radiative and turbulent processes (Morrison et al., 2012). However, these processes are poorly represented in global climate models (GCMs) for a number of reasons. The coarse spatial resolution of GCMs necessitates parameterizations of many unresolved processes that are not consistently represented. There is also a lack of consistent and reliable observations available to constrain GCM processes. As a result, Arctic mixed-phase clouds tend to glaciate too rapidly in GCMs and lead to a reduction in downward longwave (LW) radiation compared to what would have otherwise been a cloudy state. This in turn leads to a positive bias in lower tropospheric stability (LTS) and colder Arctic surface temperatures (Barton

Annual cycle observations of aerosols capable of ice formation in central Arctic clouds

“…Due to a lack of observations in the central Arctic relative to other regions, models are typically missing a local source of INPs, specifically those from marine biogenic emissions in the summer 42 , 59 . Recent Earth system model efforts reveal that marine INPs may be important in primary ice formation in Arctic clouds, even more so than dust 60 , More broadly, model spread in estimates of Arctic amplification have even been attributed to their sensitivities to INPs, and specifically summertime INP concentations 61 . However, more observations are needed to further reduce modeling uncertainties associated with INPs and their impacts on Arctic clouds.…”

Cloud Phase Simulation at High Latitudes in EAMv2: Evaluation Using CALIPSO Observations and Comparison With EAMv1

“…Moreover, the cloud liquid and ice microphysical properties in the present‐day climate can also have a significant impact on the Arctic amplification (Middlemas et al., 2020) and future global climate change (Bjordal et al., 2020; Lohmann & Neubauer, 2018; Tsushima et al., 2006). For example, it has been found that the predicted Arctic amplification strength is highly sensitive to the ice particle size and number concentration of ice nucleating particles in the present‐day environment (Tan & Storelvmo, 2019; Tan et al., 2022). Across the globe, if clouds in the present‐day climate have a lower ice water amount, the phase transition from ice to liquid would be less significant in a future warmer climate, which would result in a weaker negative cloud phase feedback and thus a warmer future climate (Murray et al., 2021; Tan et al., 2016).…”

Molecular simulations reveal that heterogeneous ice nucleation occurs at higher temperatures in water under capillary tension

“…Knowledge of the freezing efficiency of ice nucleating particles is then used to understand the formation of ice in clouds (e.g., Yang et al, 2013;Fu and Xue, 2017). Their representation in coarse-resolution models even has implications for prediction of Arctic amplification in the climate problem (Tan et al, 2022).…”