Transport Of Marine Aerosols Research Articles

Marine aerosol source regions to Prince of Wales Icefield, Ellesmere Island, and influence from the tropical Pacific, 1979–2001

AbstractUsing a coastal ice core collected from Prince of Wales (POW) Icefield on Ellesmere Island, we investigate source regions of sea ice‐modulated chemical species (methanesulfonic acid (MSA) and chloride (Cl−)) to POW Icefield and the influence of large‐scale atmospheric variability on the transport of these marine aerosols (1979–2001). Our key findings are (1) MSA in the POW Icefield core is derived primarily from productivity in the sea ice zone of Baffin Bay and the Labrador Sea, with influence from waters within the North Water (NOW) polynya, (2) sea ice formation processes within the NOW polynya may be a significant source of sea‐salt aerosols to the POW core site, in addition to offshore open water source regions primarily in Hudson Bay, and (3) the tropical Pacific influences the source and transport of marine aerosols to POW Icefield through its remote control on regional winds and sea ice variability. Regression analyses during times of MSA deposition reveal sea level pressure (SLP) anomalies favorable for opening of the NOW polynya and subsequent oceanic dimethyl sulfide production. Regression analyses during times of Cl− deposition reveal SLP anomalies that indicate a broader oceanic region of sea‐salt sources to the core site. These results are supported by Scanning Multichannel Microwave Radiometer‐ and Special Sensor Microwave/Imager‐based sea ice reconstructions and air mass transport density analyses and suggest that the marine biogenic record may capture local polynya variability, while sea‐salt transport to the site from larger offshore source regions in Baffin Bay is likely. Regression analyses show a link to tropical dynamics via an atmospheric Rossby wave.

Origins of aerosol chlorine during winter over north central Colorado, USA

AbstractThe Nitrogen, Aerosol Composition, and Halogens on a Tall Tower campaign (February–March 2011) near Boulder, Colorado, investigated nighttime ClNO2 production and processing. Virtually all particulate Cl was in the form of ionic Cl−. The size distributions of Cl− and Na+ were similar, with most of the mass in the supermicrometer size fraction, suggesting primary sources for both. Median Cl− concentrations were about half those of Na+ and Ca2+ for particle diameters centered at 1.4 and 2.5 µm. To investigate potential sources of Na+ and Cl−, four cases were studied that featured the prevalence of Na+ and Cl− and different transport pathways based on FLEXible PARTicle dispersion model (FLEXPART) retroplumes. Estimates of supermicrometer Na+ particle lifetime against deposition indicate that long‐range transport of marine aerosols could account for the observed Na+. However, measured molar ratios of Ca2+ to Na+ (0.143–0.588) compared to seawater (0.022) indicate significant contributions from crustal sources to the supermicrometer aerosol composition during these four case studies. Further, low molar ratios of Mg2+ to Na+ (0.007–0.098) relative to seawater (0.114) suggest that some of the Na+, and presumably associated Cl−, originated from non‐sea‐salt sources. The heterogeneous chemical composition of saline soils throughout the western U.S., along with the nonlinearity of wind‐driven soil deflation as a function of various surface soil properties, precludes a quantitative apportionment of soil, marine, and anthropogenic sources to the observed coarse‐fraction aerosol. Nonetheless, results suggest that deflation of saline soils was a potentially important source of particulate Cl− that sustained atmospheric ClNO2 production and associated impacts on oxidation processes over northern Colorado.

Chemistry and isotopic composition of precipitation and surface waters in Khumbu valley (Nepal Himalaya): N dynamics of high elevation basins

We monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050ma.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry and to obtain insights regarding ecosystem responses to atmospheric inputs.The major cations in the precipitation were NH4+ and Ca2+, whereas the main anion was HCO3−, which constituted approximately 69% of the anions, followed by NO3−, SO42− and Cl−. Data analysis suggested that Na+, Cl− and K+ were derived from the long-range transport of marine aerosols. Ca2+, Mg2+ and HCO3− were related to rock and soil dust contributions and the NO3− and SO42− concentrations were derived from anthropogenic sources. Furthermore, NH4+ was derived from gaseous NH3 scavenging. The isotopic composition of weekly precipitation ranged from −1.9 to −23.2‰ in δ18O, and from −0.8 to −174‰ in δ2H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation, which suggested that other water sources contributed to the stream flow.Precipitation contents for all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source.The calculated atmospheric N load (0.30kgha−1y−1) was considerably lower than the levels that were measured in other high-altitude environments. Nevertheless, the NO3− concentrations in the surface waters (from 2 to 17μeqL−1) were greater than expected based on the low N inputs from wet deposition.

Geochemical, isotopic, and mineralogical constraints on atmospheric deposition in the hyper-arid Atacama Desert, Chile

Modern atmospheric deposition across the Atacama was collected by an array of dust traps that stretched from the Pacific coast to the Andean altiplano, and the material was analyzed for its geochemical, mass and isotopic composition. The coastal trap had the second-highest insoluble mineral particle and highest soluble salt deposition rates due to significant inputs from the Morro Mejillones Range and the Pacific Ocean, respectively. The Andean trap had the highest insoluble mineral particle deposition owing to transport of weathered material, but the lowest deposition rate of soluble salts due to its distance from the ocean and anthropogenic sources. The removal of oceanic material was effective by the coastal mountains, while the westward transport of the Andean material was determined to be minimal. The atmospheric deposition in the inland traps was mainly from the local entrainment of surface material, inland anthropogenic emissions, and transport of marine aerosols. The nitrate isotopes (δ15N and Δ17O) suggested that NOx sources and NO3− chemistry shifted along the west–east transect, and were greatly impacted by anthropogenic emissions with soil NO3− being a minor source of deposited nitrogen.

Tropical Pacific Influence on the Source and Transport of Marine Aerosols to West Antarctica*

Abstract The climate of West Antarctica is strongly influenced by remote forcing from the tropical Pacific. For example, recent surface warming over West Antarctica reflects atmospheric circulation changes over the Amundsen Sea, driven by an atmospheric Rossby wave response to tropical sea surface temperature (SST) anomalies. Here, it is demonstrated that tropical Pacific SST anomalies also influence the source and transport of marine-derived aerosols to the West Antarctic Ice Sheet. Using records from four firn cores collected along the Amundsen coast of West Antarctica, the relationship between sea ice–modulated chemical species and large-scale atmospheric variability in the tropical Pacific from 1979 to 2010 is investigated. Significant correlations are found between marine biogenic aerosols and sea salts, and SST and sea level pressure in the tropical Pacific. In particular, La Niña–like conditions generate an atmospheric Rossby wave response that influences atmospheric circulation over Pine Island Bay. Seasonal regression of atmospheric fields on methanesulfonic acid (MSA) reveals a reduction in onshore wind velocities in summer at Pine Island Bay, consistent with enhanced katabatic flow, polynya opening, and coastal dimethyl sulfide production. Seasonal regression of atmospheric fields on chloride (Cl−) reveals an intensification in onshore wind velocities in winter, consistent with sea salt transport from offshore source regions. Both the source and transport of marine aerosols to West Antarctica are found to be modulated by similar atmospheric dynamics in response to remote forcing. Finally, the regional ice-core array suggests that there is both a temporally and a spatially varying response to remote tropical forcing.

Sea salt in aerosols over the southern Baltic. Part 1. The generation and transportation of marine particles

During five campaigns at sea and 11 on land in 2001–2007, aerosols were measured in the coastal zone and over the open sea in the Gdańsk Basin (southern Baltic). Sea salt concentrations were high both over Gdynia (2.0–12.2μgm−3) and at sea (1.3–14.5μgm−3). The intensity of the generation and transport of marine aerosols increased exponentially with wind speeds>5ms−1 over land and>3ms−1 over the Gulf of Gdańsk, this being most noticeable with Baltic and oceanic advection. Sea breezes were conducive to the transport of marine aerosols over land areas. The sea was also the origin of both sea salt and non-sea salt sulphate aerosols. An interesting increase in the proportion of non-sea salt-related sulphates (86.7%) was observed in spring, when the biological processes in the sea were more intense.

Development of a 2D marine aerosol transport model: Application to the influence of thermal stability in the marine atmospheric boundary layer

The present paper deals with the implementation of the Marine Aerosol Concentration Model (MACMod) in a Mediterranean coastal area. MACMod is a 2D unsteady model dedicated to the atmospheric transport of marine aerosols in the Marine Atmospheric Boundary Layer (MABL). The model predictions were compared to aerosol size distributions measured during experimental campaigns conducted in the French coastal Mediterranean area, for various experimental conditions. The results show a good agreement between the model calculations and the experimental data. In addition, the influence of the main parameters governing the transport of sea-salts in the MABL in case of offshore winds is investigated using model calculations. In particular, our work allows quantification of decrease or increase in concentrations dependent on the thermal stability conditions (compared to neutral case). It is also found that the thermal stability has an increased effect for low wind speeds. The concentration at 10 m height of submicron and supermicron aerosols show an opposite behavior with regard to the stability conditions, i.e., concentration of the former is increased for stable conditions, whereas it is decreased for the latter. When the wind speed exceeds 15 ms − 1 , the thermal stability effect is lowered.

Multi-Scale Modeling of the Corrosion of Metals under Atmospheric Corrosion

A holistic model of the atmospheric corrosion of metals is being developed. The model is based on integrating modules that define such processes as marine aerosol production by oceans and breaking surf, transport of marine aerosols across landscapes, deposition of aerosols onto structures, cleaning of surfaces by wind and rain, and the wetting and drying of surfaces throughout surface temperature and relative humidity cycles. The integration of these modules into a software framework enables the user to extract accurate estimates of surface conditions for structures located at any geographical location in Australia. Current research is aimed at developing a more fundamental approach to estimating corrosion based on the response of a metal to its environment.

Inland transport of marine aerosols in southern Sweden

The transport of marine aerosols across southern Sweden was studied using six meteorological stations in a transect from west- to east-coast. Measurements were made during dry westerlies on 10 occasions during 1995. The concentration and flux of salt in the air was measured using “salt vanes”. It is concluded that marine salt is transported along the whole transect at all occasions and that the concentration and flux of salt decrease with downwind distance from the coast as an inversed power function. The two easternmost stations show a slight increase towards the east-coast. Variability of the data is high on the west coast due to strong influence from the coastal production of aerosols. This effect diminishes along downwind forming lower, less variable concentration further inland. Statistical models based on the data are in relatively good agreement with previous models and data. Further, salt content on Scots Pine ( Pinus sylvestris, L) needles after two westerly gale occasions, in profiles from west- to east-coast, were analysed. The Cl −/Na +, Ca 2+/Na +, K +/Na +, Mg 2+/Na + and SO 4 2−/Na + ratios were studied revealing a clear downwind decrease in Ca 2+/Na + and Mg 2+/Na +, a close to sea water ratio for Cl −/Na + and an excess of SO 4 2− along the profile. Also, the importance of degree of exposure was studied concluding that the roughness of the upwind surface is an important factor for the deposition onto trees in forest edges.