On the seawater temperature dependence of the sea spray aerosol generated by a continuous plunging jet

Abstract

Key Points:• Particle concentrations decreased as seawater temperature increased to ∼9°C • Bubbles with r film < 2 mm decreased as seawater temperature increased to ∼9°C• Particle concentration was correlated with bubble density at the water surface Abstract Breaking waves on the ocean surface produce bubbles which, upon bursting, deliver seawater constituents into the atmosphere as sea spray aerosol particles. One way of investigating this process in the laboratory is to generate a bubble plume by a continuous plunging jet. We performed a series of laboratory experiments to elucidate the role of seawater temperature on aerosol production from artificial seawater free from organic contamination using a plunging jet. The seawater temperature was varied from −1.3• C to 30.1 • C, while the volume of air entrained by the jet, surface bubble size distributions, and size distribution of the aerosol particles produced was monitored. We observed that the volume of air entrained decreased as the seawater temperature was increased. The number of surface bubbles with film radius smaller than 2 mm decreased nonlinearly with seawater temperature. This decrease was coincident with a substantial reduction in particle production. The number concentrations of particles with dry diameter less than ∼1 m decreased substantially as the seawater temperature was increased from −1.3With further increase in seawater temperature (up to 30• C), a small increase in the number concentration of larger particles (dry diameter >∼0.3 m) was observed. Based on these observations, we infer that as seawater temperature increases, the process of bubble fragmentation changes, resulting in decreased air entrainment by the plunging jet, as well as the number of bubbles with film radius smaller than 2 mm. This again results in decreased particle production with increasing seawater temperature.

Climate Feedback on Aerosol Emission and Atmospheric Concentrations

“…While phytoplankton productivity and thus, e.g., DMS production depend on the water temperatures (together with light and nutrient supplies), the temperature dependence of primary aerosol emissions was recognized only in the recent years. The temperature influence was detected in laboratory experiments and confirmed by field measurements [60][61][62]. At constant wind speeds, warmer temperatures lead to higher emissions and to larger particle sizes.…”

LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles – Part 1: Principle of measurements and instrument evaluation

“…A laboratory cross-comparison of LOAC with the FIDAS 200 (Palas GmbH) aerosol counter and a custom built DMPS (differential mobility particle sizer; Salter et al, 2014) has been conducted using a temperature-controlled sea spray chamber at Stockholm University, Sweden, from 12 to 14 August 2015. All the three instruments were sampling in parallel.…”

Are breaking waves, bores, surges and jumps the same flow?

“…Further links were developed between breaking waves and steady flow configurations. These encompassed comparisons between plunging breakers and plunging jets (Cipriano and Blanchard 1981, Hubbard et al 1987, Chanson and Cumming 1994, Oguz et al 1995, Chanson et al 2002, Salter et al 2014, between spilling breakers and stationary hydraulic jumps (Longuet-Higgins 1973, Peregrine and Svendsen 1978, Madsen 1981, Brocchini et al 2001a, and between spilling breakers and translating hydraulic jumps (also called positive surges or tidal bores) (Longuet-Higgins 1973, Peregrine and Svendsen 1978, Brocchini and Peregrine 2001b. In parallel, there have been numerous discussions about the similarities and differences between stationary and translating hydraulic jumps (e.g.…”

“…A majority of such studies tested experimentally saltwater solutions, typically by gradually adding salt to freshwater: i.e., synthetic seawater (Cartmill and Su 1993, Loewen et al 1996, Bowyer 2001, Salter et al 2014) (Also Table 1). Differences have been attributed to some form of inhibited coalescence process in saltwater.…”