Arctic Sea Ice Melting Controls Sea Spray Aerosol Production

TL;DR

Arctic sea ice melting affects sea spray aerosol production, with melt ponds reducing it and ice algae possibly increasing it.

Contribution

New insights into how Arctic-specific factors like melt ponds and ice algae influence sea spray aerosol production.

Findings

Melt ponds drastically reduce sea spray aerosol production.

Ice algal microgels may enhance sea spray aerosol production.

Ambient measurements suggest at least 17% and 42% of aerosol concentrations may be attributable to sea spray.

Abstract

The loss of Arctic
Sea ice enlarges the ocean water surface exposed
to wind speed, increasing the emissions of sea spray aerosols (SSAs).
Given the unique evolution of upper ocean salinity waters and ice-associated
ecosystems, it is crucial to improve Arctic-specific SSA parametrizations
to represent the currently poorly understood feedback processes. Here,
by using Arctic ship-borne in situ aerosol tank laboratory experiments,
we study SSA produced from open ocean, open leads, and melt ponds.
We find a complex nonlinear, yet unresolved variation in SSA production
associated with salinity and organic composition. Specifically, we
find that melt ponds drastically reduce SSA production, whereas ice
algal microgels may enhance it. During the summer 2017 cruise (research
vessel Araon), we also carried out aerosol ambient measurements across
the Chukchi and East Siberian Seas. Size resolved ambient particle
number concentrations reveal at least 17% and 42% of ambient number
aerosol concentrations (N10–300 nm and N100–300 nm, respectively) are possibly attributable
to SSA. Our results may help modeling experiments using SSA parametrization
currently suffering from large uncertainty for constraining the sea
spray emission fluxes from leads, melt ponds, and salinity gradients
encountered in the Arctic Ocean.

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