Sea spray study helps predict impact of climate change

When waves break on the open ocean, they throw particles called marine aerosols into the atmosphere. These particles can be lifted miles into the air, where they can affect cloud formation and thus the Earth’s radiation balance. This balance between the amount of radiative energy emitted, absorbed, and reflected by the Earth’s surface and the atmosphere strongly affects the climate.

Sea spray aerosols, the most abundant natural aerosols in Earth’s atmosphere, consist primarily of salt, but they can also contain traces of other chemical compounds, and even biologically produced proteins and sugars.

These molecules from marine organisms can change how aerosols affect Earth’s climate, and even the health of plants and animals, by altering particle size, concentration, chemical composition and tendency to absorb water. But previous studies have not conclusively established average levels of organic content in sea spray.

Michael J. Lawler and colleagues fill this gap using data from four deployments of NOAA’s Particle Analysis by Laser Mass Spectrometry (PALMS) instrument during NASA’s Atmospheric Tomography (ATom) mission over remote areas of the Atlantic and Pacific Oceans between 2016 and 2018. The results are published in the journal AGU Progress.

PALMS measured the mass of organic molecules in the sampled aerosols, allowing researchers to infer the extent to which life influences the composition of sea spray aerosols.

They found that overall, the organic mass fraction of sea spray aerosols is low (less than 10% in most cases), although smaller particles contain higher proportions of organic matter.

They also found little seasonal variability in the organic mass fraction, a clear sign that living organisms, whose abundance waxes and wanes with the seasons, were not really involved. The researchers observed two exceptions in the Canadian Arctic and in the southern mid- and high latitudes, where they observed summer maxima in the organic mass fraction.

The authors also found a much larger organic component in sea spray aerosols higher in the troposphere, which they say is likely due to atmospheric chemical reactions and not the original composition of the aerosols emitted by ocean waves.

Future topics include the role of organic molecules in the production of very small aerosols (less than 0.2 micrometers) in sea spray, as well as better reconciliation of observations and numerical models of organic matter in sea spray aerosols.

This article is republished with kind permission from Eos, hosted by the American Geophysical Union. Read the original article here.