26 May 2021

26 May 2021

Review status: this preprint is currently under review for the journal ACP.

A numerical framework for simulating episodic emissions of high-temperature marine INPs

Isabelle Steinke1, Paul J. DeMott2, Grant Deane3, Thomas C. J. Hill2, Mathew Maltrud4, Aishwarya Raman1, and Susannah M. Burrows1 Isabelle Steinke et al.
  • 1Atmospheric Sciences & Global Change, Pacific Northwest National Laboratory, Richland, Washington, USA
  • 2Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA
  • 3Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
  • 4Climate Ocean Sea Ice Modeling, Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Abstract. We present a framework for estimating concentrations of episodically elevated high-temperature marine ice nucleating particles (INPs) in the sea surface microlayer and their subsequent emission into the atmospheric boundary layer. These episodic INPs have been observed in multiple ship-based and coastal field campaigns, but the processes controlling their ocean concentrations and transfer to the atmosphere are not yet fully understood. We use a combination of empirical constraints and simulation outputs from an Earth System Model to explore different hypotheses for explaining the variability of INP concentrations, and the occurrence of episodic INPs, in the marine atmosphere. In our calculations, we examine two proposed oceanic sources of high-temperature INPs: heterotrophic bacteria and marine biopolymer aggregates (MBPAs). Furthermore, we assume that the emission of these INPs is determined by the production of supermicron sea spray aerosol formed from jet drops, with an entrainment probability that is described by Poisson statistics. The concentration of jet drops is derived from the number concentration of supermicron sea spray aerosol calculated from model runs. We then derive the resulting number concentrations of marine high-temperature INPs (≥ 253 K) in the atmospheric boundary layer and compare their variability to atmospheric observations of INP variability. Specifically, we compare against concentrations of episodically occurring high-temperature INPs observed during field campaigns in the Southern Ocean, the Equatorial Pacific, and the North Atlantic.

We find that heterotrophic bacteria and MBPAs acting as INPs provide only a partial explanation for the observed high INP concentrations. We note, however, that there are still substantial knowledge gaps, particularly concerning the identity of the oceanic INPs contributing most frequently to episodic high-temperature INPs, their specific ice nucleation activity, and the enrichment of their concentrations during the sea-air transfer process. Therefore, targeted measurements investigating the composition of these marine INPs as well as drivers for their emission are needed, ideally in combination with modeling studies focused on the potential cloud impacts of these high-temperature INPs.

Isabelle Steinke et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-316', Anonymous Referee #2, 24 Jun 2021
  • RC2: 'Comment on acp-2021-316', Anonymous Referee #1, 03 Aug 2021
  • AC1: 'Comment on acp-2021-316', Isabelle Steinke, 09 Oct 2021

Isabelle Steinke et al.

Isabelle Steinke et al.


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Short summary
Over the oceans, sea spray aerosol is an important source of particles that may initiate the formation of cloud ice, which then has implications for the radiative properties of marine clouds. In our study, we focus on marine biogenic particles that are emitted episodically and develop a numerical framework to describe these emissions. We find that further cloud-resolving model studies and targeted observations are needed to fully understand the climate impacts from marine biogenic particles.