Marine biogenic aerosols and their effects on aerosol-cloud interactions over the Southern Ocean: a review

The Southern Ocean (SO) plays an important role in the global climate system. Changes in SO biogeochemistry and marine ecosystems may influence the distribution of atmospheric aerosols and clouds and impact the climate system. We reviewed current knowledge on the interactions between marine aerosols and clouds over the SO. We focused on marine primary and secondary organic aerosols and summarized their characteristics, processes and roles as cloud condensation nuclei and ice nuclei. We described in detail the interactions between the marine ecosystem, aerosols and clouds. We discussed marine productivity, formation of marine biogenic aerosols and interactions between aerosols, clouds and climate. We explored the impact of climate change on SO marine ecosystem productivity and aerosol–cloud–climate feedback. Marine biogenic aerosols could impact the radiation budget and oceanic low-level clouds over the SO. This study contributes towards an improved understanding of marine productivity, aerosol-cloud interactions and climate change in the SO. The SO may respond to climate change in varying degrees. More studies are urgently needed to support accurate forecasts of future changes in the SO

Seasonal variations of sulfur aerosols at Zhongshan Station, East Antarctica

Observations of atmospheric methane-sulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4 2−) from December 2010 to November 2011 at Zhongshan Station are presented in this paper. MSA and nss-SO4 2− average concentrations were 24.2 ± 37.9 ng·m-3 (0.5–158.3 ng·m-3 ) and 53.0 ± 82.6 ng·m-3 (not detected [n.d.]) – 395.4 ng·m-3 ), respectively. Strong seasonal variations of MSA and nss-SO4 2−, with maxima in austral summer and minima in winter, were examined. The high concentrations of sulfur compounds in December may be attributed the dimethyl sulfide (DMS) emissions from the marginal ice zone, when open water near the sampling site was important in impacting the sulfur species of January and February at Zhongshan Station. In austral winter, there was almost no phytoplanktonic activity in offshore waters, and atmospheric sulfur compounds likely had long-range transport sources

Uptake selectivity of methanesulfonic acid (MSA) on fine particles over polynya regions of the Ross Sea, Antarctica

The uptake of methanesulfonic acid (MSA) on existing particles is a major route of the particulate MSA formation, however, MSA uptake on different particles is still lacking in knowledge. Characteristics of MSA uptake on different aerosol particles were investigated in polynya (an area of open sea water surrounded by ice) regions of the Ross Sea, Antarctica. Particulate MSA mass concentrations, as well as aerosol population and size distribution, were observed simultaneously for the first time to access the uptake of MSA on different particles. The results show that MSA mass concentration does not always reflect MSA particle population in the marine atmosphere. MSA uptake on aerosol particle increases the particle size and changes aerosol chemical composition, but it does not increase the particle population. The uptake rate of MSA on particles is significantly influenced by aerosol chemical properties. Sea salt particles are beneficial for MSA uptake, as MSA-Na and MSA-Mg particles are abundant in the Na and Mg particles, accounting for 0.43 +/- 0.21 and 0.41 +/- 0.20 of the total Na and Mg particles, respectively. However, acidic and hydrophobic particles suppress the uptake of MSA, as MSA-EC (elemental carbon) and MSA-SO42- particles account for only 0.24 +/- 0.68 and 0.26 +/- 0.47 of the total EC and SO42- particles, respectively. The results extend the knowledge of the formation and environmental behavior of MSA in the marine atmosphere.Peer reviewe

DMS sea-to-air fluxes and their influence on sulfate aerosols over the Southern Ocean, south-east Indian Ocean and north-west Pacific Ocean

Environmental context The ocean-produced dimethyl sulfide (DMS) molecule is thought to affect cloud formation and the solar radiation budget at the Earth's surface, hence playing an important role in regulating climate. In this study, we calculated the DMS sea-to-air flux across the Southern Ocean, south-east Indian Ocean and north-west Pacific Ocean, and analysed the influence of DMS fluxes on sulfate aerosols. These results improved our understanding of the effects of DMS emissions on sulfate compounds in the atmosphere over the global ocean. Oceanic dimethyl sulfide (DMS) is the most abundant biogenic sulfur compound emitted into the atmosphere and could indirectly regulate the global climate by impacting end product sulfate aerosols. DMS emissions and their influence on sulfate aerosols, i.e. methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO42-), were investigated over the Atlantic Ocean and Indian Ocean sectors of the Southern Ocean (SO), the south-east Indian Ocean, and the north-west Pacific Ocean from February to April 2014 during the 30th Chinese National Antarctic Research Expedition. We found a strong large-scale DMS source in the marginal sea ice zone from 34 degrees W to 14 degrees E of the SO (south of 60 degrees S), in which the mean flux was 49.0 +/- 65.6 mu mol m(-2) d(-1) (0.6-308.3 mu mol m(-2) d(-1), n = 424). We also found a second large-scale DMS source in the South Subtropical Front (similar to 40 degrees S, up to 50.8 mu mol m(-2) d(-1)). An inconsistency between concentrations of atmospheric sulfate compounds and DMS emissions along the cruise track was observed. The horizontal advection of air masses was likely the main reason for this discrepancy. Finally, the biological exposure calculation results also indicated that it is very difficult to observe a straightforward relationship between oceanic biomass and atmospheric MSA

Seasonal variations in aerosol compositions at Great Wall Station in Antarctica

High volume aerosol samplers at Great Wall Station in Antarctica were used to collect 73 aerosol samples between January 2012 and November 2013. The main ions in these aerosol samples, Cl−, NO3−, SO4 2−, Na+, K+, Ca2+, Mg2+, NH4+, as well as methane sulfonic acid, were analyzed using ion chromatography. Trace metals in these samples, including Pb, Cu, Cd, V, Zn, Fe, and Al, were determined by inductively-coupled plasma mass spectrometry. Results showed that sea salt was the main component in aerosols at Great Wall Station. Most ions exhibited significant seasonal variations, with higher concentrations in summer and autumn than in winter and spring. Variations in ions and trace metals were related to several processes (or sources), including sea salt emission, secondary aerosol formation, and anthropogenic pollution from both local and distant sources. The sources of ions and trace metals were identified using enrichment factor, correlation, and factor analyses. Clearly, Na+, K+, Ca2+, and Mg2+ were from marine sources, while Cu, Pb, Zn, and Cd were from anthropogenic pollution, and Al and V were mainly from crustal sources

KEGG_Extractor: An Effective Extraction Tool for KEGG Orthologs

The KEGG Orthology (KO) database is a widely used molecular function reference database which can be used to conduct functional annotation of most microorganisms. At present, there are many KEGG tools based on the KO entries for annotating functional orthologs. However, determining how to efficiently extract and sort the annotation results of KEGG still hinders the subsequent genome analysis. There is a lack of effective measures used to quickly extract and classify the gene sequences and species information of the KEGG annotations. Here, we present a supporting tool: KEGG_Extractor for species-specific genes extraction and classification, which can output the results through an iterative keyword matching algorithm. It can not only extract and classify the amino acid sequences, but also the nucleotide sequences, and it has proved to be fast and efficient for microbial analysis. Analysis of the ancient Wood Ljungdahl (WL) pathway through the KEGG_Extractor reveals that ~226 archaeal strains contained the WL pathway-related genes. Most of them were Methanococcus maripaludis, Methanosarcina mazei and members of the Methanobacterium, Thermococcus and Methanosarcina genus. Using the KEGG_Extractor, the ARWL database was constructed, which had a high accuracy and complement. This tool helps to link genes with the KEGG pathway and promote the reconstruction of molecular networks. Availability and implementation: KEGG_Extractor is freely available from the GitHub

First High-Frequency Underway Observation of DMS Distribution in the Southern Ocean during Austral Autumn

We investigate the distribution of dimethyl sulfide (DMS) in the Southern Ocean’s (50° W to 170° W) surface water, including the Antarctic Peninsula and the marginal sea ice zone (MIZ) in the Ross and Amundsen Seas. This is the first high-frequency observation conducted in the austral autumn (in April) in the Southern Ocean. The mean DMS concentration was 2.7 ± 2.5 nM (1 σ) for the entire study area. Noticeably enhanced DMS (5 to 28 nM) concentrations were observed in the MIZ around the Ross and Amundsen Seas and the coastal regions in the Antarctic Peninsula; this could be attributed to biological production of local ice algae, which appears to be supplied with nutrients from glacial or sea ice melt water. These observed DMS inventories were significantly higher (an order of magnitude) than current climatological DMS inventories. The local DMS sources being transported outward from the polynyas, where strong bloom occurs during summer, could result in larger discrepancies between observed DMS and climatological DMS in the MIZ area (in the Amundsen Sea). Overall, this study is the first to highlight the significance of the underestimation of current DMS fluxes in the austral autumn, which consequently results in significant errors in the climate models

Winter season Southern Ocean distributions of climate-relevant trace gases

Climate-relevant trace gas air-sea exchange exerts an important control on air quality and climate, especially in remote regions of the planet such as the Southern Ocean. It is clear that polar regions exhibit seasonal trends in productivity and biogeochemical cycling, but almost all of the measurements there are skewed to summer months. If we want to understand how the Southern Ocean effects the balance of climate through trace gas air-sea exchange, it is essential to expand our measurement database over greater temporal and spatial scales, including all seasons. Therefore, in this study, we report measured concentrations of dimethylsulphide (DMS, and related sulphur compounds) and isoprene in the Atlantic sector of the Southern Ocean during the winter to understand the spatial and temporal distribution in comparison to current knowledge and climatological calculations for the Southern Ocean. The observations of isoprene are the first in the winter season in the Southern Ocean. We find that concentrations and fluxes of DMS and isoprene in the investigated area are generally lower than those presented or calculated in currently used climatologies and models. More data is urgently needed to better interpolate climatological values and validate process-oriented models, as well as to explore how finer measurement resolution, both spatially and temporally, can influence air-sea flux calculations

First High-Frequency Underway Observation of DMS Distribution in the Southern Ocean during Austral Autumn

We investigate the distribution of dimethyl sulfide (DMS) in the Southern Ocean’s (50° W to 170° W) surface water, including the Antarctic Peninsula and the marginal sea ice zone (MIZ) in the Ross and Amundsen Seas. This is the first high-frequency observation conducted in the austral autumn (in April) in the Southern Ocean. The mean DMS concentration was 2.7 ± 2.5 nM (1 σ) for the entire study area. Noticeably enhanced DMS (5 to 28 nM) concentrations were observed in the MIZ around the Ross and Amundsen Seas and the coastal regions in the Antarctic Peninsula; this could be attributed to biological production of local ice algae, which appears to be supplied with nutrients from glacial or sea ice melt water. These observed DMS inventories were significantly higher (an order of magnitude) than current climatological DMS inventories. The local DMS sources being transported outward from the polynyas, where strong bloom occurs during summer, could result in larger discrepancies between observed DMS and climatological DMS in the MIZ area (in the Amundsen Sea). Overall, this study is the first to highlight the significance of the underestimation of current DMS fluxes in the austral autumn, which consequently results in significant errors in the climate models

Unravelling Surface Seawater DMS Concentration and Sea‐To‐Air Flux Changes After Sea Ice Retreat in the Western Arctic Ocean

Key Points: • Surface seawater dimethylsulfide (DMS) concentrations remain unchanged after sea ice retreat in the western Canada Basin • Increased wind speed is a critical factor driving the enhancement of dimethylsulfide (DMS) flux after sea ice retreat at high latitudes in the Arctic Ocean • Nutrient supply is hypothesized to significantly impact dimethylsulfide (DMS) distribution in the western Arctic Ocean Abstract: The receding of the seasonal ice cover in the Arctic due to climate change has been predicted by models to increase climate-active biogenic trace gas emissions, specifically those of dimethylsulfide (DMS). However, insufficient DMS measurements are currently available to either support or refute this hypothesis and to fully understand the various responses of oceanic DMS in a rapidly changing Arctic Ocean environment. Here, we present high-resolution surface water DMS data collected in the summer of 2014 in combination with a suite of ancillary variables including sea ice cover, salinity, and nutrients. We show that surface seawater DMS concentrations, generally below 0.5 nmol L−1, remained unchanged in the Canada Basin after sea ice retreat probably due to insufficient nutrients supply to the upper mixed layer and resulting low primary production. Moreover, in the Chukchi shelf region, DMS concentrations decreased following a phytoplankton bloom due to the rapid depletion and slow resupply of nutrients. Although the DMS sea-to-air fluxes were not high from a global perspective, they increased by a factor of 4-fold after sea ice retreat in the Arctic Ocean high latitudes. This increase in DMS flux was mainly driven by increased wind speed. This work provides unique observations and insights on how surface seawater DMS and flux to the atmosphere may change in the future Arctic Ocean