A Mesocosm Double Feature: Insights into the Chemical Makeup of Marine Ice Nucleating Particles

Abstract

The abundance of atmospheric ice nucleating particles (INPs) is a source of uncertainty for numerical representation of ice-phase transitions in mixed-phase clouds. While sea spray aerosol (SSA) exhibits less ice nucleating (IN) ability than terrestrial aerosol, marine INP emissions are linked to oceanic biological activity and are potentially an important source of INPs over remote oceans. Inadequate knowledge of marine INP identity limits the ability to parameterize this complex INP source. A previous manuscript described abundances of marine INPs in relation to several aerosol composition and ocean biology observations during two laboratory mesocosm experiments. In this study, the abundances and chemical and physical properties of INPs found during the same mesocosm experiments were directly probed in SSA, seawater, and surface microlayer samples. Two unique marine INP populations were found: 1) dissolved organic carbon INPs are suggested to be composed of IN-active molecules, and 2) particulate organic carbon INPs are attributed as intact cells or IN-active microbe fragments. Both marine INP types are likely to be emitted into SSA following decay of phytoplankton biomass when 1) the surface microlayer is significantly enriched with exudates and cellular detritus and SSA particles are preferentially coated with IN-active molecules or 2) diatom fragments and bacteria are relatively abundant in seawater and therefore more likely transferred into SSA. These findings inform future efforts for incorporating marine INP emissions into numerical models and motivate future studies to quantify specific marine molecules and isolate phytoplankton, bacteria, and other species that contribute to these marine INP types.

Abundance of Biological Ice Nucleating Particles in the Mississippi and Its Major Tributaries

“…It can also be seen that the warmer-temperature-active INPs are more heat sensitive and that the effect is lost around −12 • C (Figure 2 and Figure S1); presumably, at colder temperatures INPs are a mix of heat-resistant organic and mineral INPs [12]. The size observations agree with previous work on freshwater INPs in Wales [31], marine INPs [17,20], precipitation [35][36][37], and recent studies showing that ice nucleating fungi and pollen release copious numbers of small (e.g., <15 nm) cell-free INPs [38][39][40]. (Figure 1).…”

“…In addition to ongoing interest into the action of both mineral dusts and soot [6][7][8], the role of the soil organic matter, which includes INPs produced by the decomposer community, as a source of atmospheric INPs is now being more closely examined [9][10][11][12]; pioneering work identified the litter layer, in particular, as a prodigious source of biological INPs in diverse global ecotypes [13,14]. By contrast, while oceans comprise 71% of the Earth's surface area and emit INPs within sea spray-mainly by bubble bursting-they are only now being investigated more systematically [15][16][17][18][19][20][21]. Until recently, the only systematic study of INPs in the marine boundary layer was that undertaken by Bigg [22].…”

Characteristics of Ice Nucleating Particles in and Around California Winter Storms

“…Thus, we also show the Niemand et al () dust fit line reduced by this factor (dashed line) to match what the CFDC would be expected to measure for dust INPs. We also note that the “clean marine fit” is thought to represent exudate marine INPs, versus microbial, heat‐labile, episodic INPs that are active at warmer temperatures (McCluskey, et al, ). The vertical purple bars show the range in values from DeMott et al (), a separate clean marine INP data set that was not used to generate the McCluskey et al paramaterization.…”

“…Thus, other INP sources could also be important contributors to the INP budget during these storms. Specifically, oceanic aerosol could be a potential source of INPs (McCluskey et al, ; McCluskey et al, ), especially since these storm systems travel for thousands of miles over the ocean and are associated with strong onshore flow leading to increased wave breaking. However, these marine INPs, while biogenic (McCluskey, Ovadnevaite , et al, ), are much less efficient ice nucleators than dust or terrestrially‐sourced biological (intended to mean microbial herein) particles (DeMott et al, ), and thus could lead to different cloud and precipitation properties if they were the dominant or only INP source.…”

Observations of Ice Nucleating Particles Over Southern Ocean Waters

“…Irish et al () found that INEs in Canadian Arctic SML samples were smaller than 0.2 μm and heat labile. From laboratory mesocosm experiments, McCluskey, Hill et al () proposed that marine INPs comprised two types: (1) particulate organic carbon INPs (POC INPs) that are heat labile and larger than 0.2 μm and (2) dissolved organic carbon INPs (DOC INPs) that are refractory (i.e., heat stable) and smaller than 0.2 μm. Our understanding of the biological processes that control the production of INEs in seawater and the physicochemical processes that govern their release in SSA remains extremely limited.…”