Formation and global distribution of sea-surface microlayers

Abstract

Abstract.Results from a study of surfactants in the seasurface microlayer (SML) in different regions of the ocean (subtropical, temperate, polar) suggest that this interfacial layer between the ocean and atmosphere covers the ocean's surface to a significant extent. New, experimentally-derived threshold values at which primary production acts as a significant source of natural surfactants to the microlayer are coupled with a wind speed threshold at which the SML is presumed to be disrupted, and the results suggest that surfactant enrichment in the SML is greater in oligotrophic regions of the ocean than in more productive waters. Furthermore, surfactant enrichments persisted at wind speeds of up to 10 m s −1 , without any observed depletion above 5 m s −1 . This suggests that the SML is stable enough to exist even at the global average wind speed of 6.6 m s −1 . Using our observations of the surfactant enrichments at various trophic levels and wind states, global maps of primary production and wind speed allow us to extrapolate the ocean's SML coverage . The maps indicate that wide regions of the Pacific and Atlantic Oceans between 30 • N and 30 • S may be more significantly covered with SML than north of 30 • N and south of 30 • S, where higher productivity (spring/summer blooms) and wind speeds exceeding 12 m s −1 may prevent extensive SML formation.

Atmospheric deposition of methanol over the Atlantic Ocean

“…Microorganisms and dissolved organic matter tend to be enriched in the ∼0.1-mm-thick aqueous molecular sublayer (34,35). This microlayer covers both the productive regions and the oligotrophic waters and at wind speeds of up to ∼10 m·s −1 (36). Breaking waves temporally disrupt the surface, but a coherent microlayer appears to reform within seconds, in part due to efficient scavenging of surface active organic materials from bulk water by rising bubbles (37).…”

High-resolution variability of the enrichment of fluorescence dissolved organic matter in the sea surface microlayer of an upwelling region

“…Physical parameters such as high salinity, temperature, wind force, solar and UV radiation also control the enrichment of DOM in the SML. In particular, wind speed and primary productivity play a crucial role in the enrichment of surface-active DOM (Wurl et al, 2011b). At low wind speeds, surface enrichment can be sustained through diffusive transport of surface-active compounds due to the stability of the SML.…”

“…All materials exchanged between the ocean and atmosphere, including gases, particulate organic matter, and sea salt, have to pass through the SML (Liss and Duce, 2005). With a total thickness between 1 µm and 1000 µm, depending on the sampling technique (Shinki et al, 2012) and region of interest (Hardy, 1982), the SML remains sufficiently stable at a global average wind speed of 6.6 m s -1 (Wurl et al, 2011b) to control the rate of air-sea exchange of gases and heat, highlighting its global relevance. It is well established that the SML has unique physical, chemical, and biological properties that differ from those of the wellmixed underlying water masses (Hardy, 1982;Cunliffe et al, 2013).…”

Distribution of surfactants in sea-surface microlayer and atmospheric aerosols at selected coastal area of Peninsular Malaysia

“…Meanwhile, phytoplankton exudates in SML could contributes to accumulation of surfactants in atmospheric aerosols. Phytoplankton emitting organic compounds such as dimethyl-sulphide (DMS), lipids and proteins which may leads to the formation of marine salt, transferred to atmosphere through air-gas exchange [9]. …”

“…The SML has been considered to play a significant role in transportation of contaminants in marine environment and has recognized to influence the biogeochemical cycle in atmosphere [9]. In recent years, interest in this compartment has arisen through a variety of issues mainly derived from its enrichment in both organic and inorganic substances [10].…”