scholarly journals Estimation of reactive inorganic iodine fluxes in the Indian and Southern Ocean marine boundary layer

2020 ◽  
Vol 20 (20) ◽  
pp. 12093-12114
Author(s):  
Swaleha Inamdar ◽  
Liselotte Tinel ◽  
Rosie Chance ◽  
Lucy J. Carpenter ◽  
Prabhakaran Sabu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Marine Boundary Layer ◽  
Polar Front ◽  
Sea Surface ◽  
Optical Absorption Spectroscopy ◽  
Surface Seawater ◽  
Significance Level ◽  
Iodine Species ◽  
Iodine Chemistry

Abstract. Iodine chemistry has noteworthy impacts on the oxidising capacity of the marine boundary layer (MBL) through the depletion of ozone (O3) and changes to HOx (OH∕HO2) and NOx (NO∕NO2) ratios. Hitherto, studies have shown that the reaction of atmospheric O3 with surface seawater iodide (I−) contributes to the flux of iodine species into the MBL mainly as hypoiodous acid (HOI) and molecular iodine (I2). Here, we present the first concomitant observations of iodine oxide (IO), O3 in the gas phase, and sea surface iodide concentrations. The results from three field campaigns in the Indian Ocean and the Southern Ocean during 2015–2017 are used to compute reactive iodine fluxes in the MBL. Observations of atmospheric IO by multi-axis differential optical absorption spectroscopy (MAX-DOAS) show active iodine chemistry in this environment, with IO values up to 1 pptv (parts per trillion by volume) below latitudes of 40∘ S. In order to compute the sea-to-air iodine flux supporting this chemistry, we compare previously established global sea surface iodide parameterisations with new region-specific parameterisations based on the new iodide observations. This study shows that regional changes in salinity and sea surface temperature play a role in surface seawater iodide estimation. Sea–air fluxes of HOI and I2, calculated from the atmospheric ozone and seawater iodide concentrations (observed and predicted), failed to adequately explain the detected IO in this region. This discrepancy highlights the need to measure direct fluxes of inorganic and organic iodine species in the marine environment. Amongst other potential drivers of reactive iodine chemistry investigated, chlorophyll a showed a significant correlation with atmospheric IO (R=0.7 above the 99 % significance level) to the north of the polar front. This correlation might be indicative of a biogenic control on iodine sources in this region.

scholarly journals Estimation of Reactive Inorganic Iodine Fluxes in the Indian and Southern Ocean Marine Boundary Layer

2020 ◽  
Author(s):  
Swaleha Inamdar ◽  
Liselotte Tinel ◽  
Rosie Chance ◽  
Lucy J. Carpenter ◽  
Prabhakaran Sabu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Marine Boundary Layer ◽  
Molecular Iodine ◽  
Polar Front ◽  
Sea Surface ◽  
Surface Seawater ◽  
Significance Level ◽  
Iodine Species ◽  
Iodine Chemistry

Abstract. Iodine chemistry has noteworthysignificant impacts on the oxidising capacity of the marine boundary layer (MBL) through the depletion of ozone (O3) and changes to HOx (OH/HO2) and NOx (NO/NO2) ratios. Hitherto, studies have shown that the reaction of atmospheric O3 with surface seawater iodide (I−) contributes to the flux of iodine species into the MBL mainly as hypoiodous acid (HOI) and molecular iodine (I2). Here, we present the first concomitant observations of iodine oxide (IO), O3 in the gas phase, and sea surface iodide concentrations. The results from three field campaigns in the Indian Ocean and the Southern Ocean during 2014–2017 are used to compute reactive iodine fluxes to the MBL. Observations of atmospheric IO by MAX-DOAS show active iodine chemistry in this environment, with IO values up to 1 pptv (parts per trillion by volume) below latitudes of 40° S. In order to compute the sea-to-air iodine flux supporting this chemistry, we compare previously established global sea surface iodide parameterisations with new, region-specific parameterisations based on the new iodide observations. This study shows that regional changes in salinity and sea surface temperature play a role in surface seawater iodide estimation. Sea-air fluxes of HOI and I2, calculated from the atmospheric ozone and seawater iodide concentrations (observed and predicted), failed to adequately explain the detected IO in this region. This discrepancy highlights the need to measure direct fluxes of inorganic and organic iodine species in the marine environment. Amongst other potential drivers of reactive iodine chemistry investigated, chlorophyll-a showed a significant correlation with atmospheric IO (R = 0.7 above the 99 % significance level) to the north of the polar front. This correlation might be indicative of a biogenic control on iodine sources in this region.

Iodine chemistry in the tropical and remote open ocean marine boundary layer

2020 ◽  
Author(s):  
Swaleha Inamdar ◽  
Liselotte Tinel ◽  
Rosie Chance ◽  
Lucy Jane Carpenter ◽  
Sabu Prabhakaran ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Kinetic Model ◽  
Southern Ocean ◽  
Tropospheric Ozone ◽  
Marine Boundary Layer ◽  
Sea Surface ◽  
Iodine Species ◽  
Ocean Region ◽  
Inorganic Iodine

<p>Iodine chemistry plays an essential role in controlling the radiation budget by changing various atmospheric parameters. Iodine in the atmosphere is known to cause depletion of ozone via catalytic reaction cycles. It alters the atmospheric oxidation capacity, and lead to ultrafine particle formation that acts as potential cloud condensation nuclei. The ocean is the primary source of iodine; it enters the atmosphere through fluxes of gaseous reactive iodine species. At the ocean surface, seawater iodide reacts with tropospheric ozone (gas) to form inorganic iodine species in gaseous form. These species namely, hypoiodous acid (HOI) and molecular iodine (I<sub>2</sub>) quickly photolyse to release reactive iodine (I) in the atmosphere. This process acts as a significant sink for tropospheric ozone contributing to ~16% ozone loss throughout the troposphere. Reactive iodine released in the atmosphere undergoes the formation of iodine monoxide (IO) or higher oxides of iodine (I<sub>x</sub>O<sub>x</sub>) via self-recombination reactions. It is known that inorganic iodine fluxes (HOI and I<sub>2</sub>) contribute to 75% of the detected IO over the Atlantic Ocean. However, we did not observe this from ship-based MAX-DOAS studies between 2014-2017. At present, there are no direct observations of inorganic iodine (HOI; few for I<sub>2</sub>) and are estimated via empirical methods derived from the interfacial kinetic model by Carpenter et al. in 2013. Based on the kinetic model, estimation of HOI and I<sub>2</sub> fluxes depends on three parameters, namely, ozone concentration, surface iodide concentration, and the wind speed. This parameterisation for inorganic fluxes assumes a sea surface temperature (SST) of 293 K and has limiting wind speed conditions. Since the parameterisation conditions assumed SST of 293 K higher uncertainties due to errors in activation energy creeps in the estimation of HOI flux compared to I<sub>2</sub> as the flux of HOI is ~20 times greater than that of I<sub>2</sub>. For three consecutive expeditions in the Indian and Southern Ocean, we detected ~1 pptv of IO in the marine boundary layer. These levels are not explained by the calculated inorganic fluxes by using observed and predicted sea surface iodide concentrations. This method of iodine flux estimation is currently used in all global models, along with the MacDonald et al. 2014 iodide estimation method. Model output using these parameterisations have not been able to match the observed IO levels in the Indian and Southern Ocean region. This discrepancy suggests that the process of efflux of iodine to the atmosphere may not be fully understood, and the current parametrisation does not do justice to the observations. It also highlights that the flux of organic iodine may also play a role in observed IO levels, especially in the Indian Ocean region. A correlation of 0.7 was achieved above the 99% confidence limit for chlorophyll-a with observed IO concentration in this region. There is a need to carry more observations to improve the estimation technique of iodine sea-air flux thus improving model predictions of IO in the atmosphere.</p>

Marine Aerosol Iodine Chemistry: The Importance of Soluble Organic Iodine

2005 ◽  
Vol 2 (4) ◽  
pp. 295 ◽  
Author(s):  
Alex R. Baker
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Marine Aerosol ◽  
Radiative Balance ◽  
Iodine Species ◽  
Ozone Destruction ◽  
Organic Iodine ◽  
Iodine Chemistry ◽  
Inorganic Iodine ◽  
Complex Chemistry

Environmental Context.Ozone concentrations play a large part in controlling the oxidation capacity of the marine boundary layer, while the production of new aerosol particles affects atmospheric radiative balance. Iodine has a complex chemistry in the marine atmosphere which impacts on both these processes. Much of this iodine chemistry, especially the chemical speciation of iodine in aerosol, is only poorly understood. This study explores the occurrence and abundance of organic forms of iodine, a topic that has received very little attention to date. Abstract.Iodine has a complex chemistry in aerosols in the marine boundary layer (MBL), and is involved in both ozone destruction and new aerosol particle formation processes. Work in this area has focussed almost exclusively on inorganic iodine chemistry. Results from two research cruises in the Atlantic Ocean, covering wide longitude (60°W to 0°W) and latitude (50°N to 50°S) ranges indicate that soluble organic iodine species are both widespread and abundant in marine aerosol. The reactivity of these species is yet to be determined, but may influence the concentrations of some aerosol inorganic iodine species, and may also impact on MBL ozone destruction reactions.

Sea-Surface Chemistry and Its Impact on the Marine Boundary Layer

2012 ◽  
Vol 46 (19) ◽  
pp. 10385-10389 ◽  
Author(s):  
D. J. Donaldson ◽  
Christian George
Keyword(s):  
Boundary Layer ◽  
Surface Chemistry ◽  
Marine Boundary Layer ◽  
Sea Surface

Can Marine Cloud Brightening Reduce Sea-Surface Temperatures to Moderate Extreme Hurricanes and Typhoons?

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Salter SH ◽  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Sea Water ◽  
Cloud Condensation Nuclei ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Marine Stratocumulus ◽  
Surface Temperatures ◽  
Stratocumulus Clouds ◽  
Cloud Tops

Elevated sea-surface temperatures are a necessary but not sufficient requirement for the formation of hurricanes and typhoons. This paper suggests a way to exploit this. Twomey [1] showed that cloud reflectivity depends on the size-distribution of cloud drops, with a large number of small drops reflecting more than a smaller number of larger ones. Mid-ocean air is cleaner than over land. Latham [2-4] suggested that reflectivity of marine stratocumulus clouds could be increased by releasing a submicron spray of filtered sea water into the bottom of the marine boundary layer. The salt residues left after evaporation would be mixed by turbulence through the full depth of the marine boundary layer and would be ideal cloud condensation nuclei. Those that reached a height where the air had a super-saturation above 100% by enough to get over the peak of the Köhler curve would produce an increased number of cloud drops and so trigger the Twomey effect. The increase in reflection from cloud tops back out to space would cool sea-surface water. We are not trying to increase cloud cover; we just want to make existing cloud tops whiter. The spray could be produced by wind-driven vessels cruising chosen ocean regions. The engineering design of sea-going hardware is well advanced. This paper suggests a way to calculate spray quantities and the number and cost of spray vessels to achieve a hurricane reduction to a more acceptable intensity. It is intended to show the shape of a possible calculation with credible if not exact assumptions. Anyone with better assumptions should be able to follow the process.

scholarly journals A broadband cavity ringdown spectrometer for in-situ measurements of atmospheric trace gases

2005 ◽  
Vol 5 (3) ◽  
pp. 3491-3532 ◽  
Author(s):  
M. Bitter ◽  
S. M. Ball ◽  
I. M. Povey ◽  
R. L. Jones
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Marine Boundary Layer ◽  
Thermal Dissociation ◽  
Optical Absorption Spectroscopy ◽  
Integration Time ◽  
Research Station ◽  
Absorption Bands ◽  
Optical Extinction ◽  
Cavity Ringdown

Abstract. This paper describes a broadband cavity ringdown spectrometer and its deployment during the 2002 North Atlantic Marine Boundary Layer Experiment (NAMBLEX) to measure ambient concentrations of NO3, N2O5, I2 and OIO at the Mace Head Atmospheric Research Station, Co. Galway, Ireland. The effective absorption path lengths accessible with the spectrometer generally exceeded 10 km, enabling sensitive localised ''point'' measurements of atmospheric absorbers to be made adjacent to the other instruments monitoring chemically related species at the same site. For the majority of observations, the spectrometer was used in an open path configuration thereby avoiding surface losses of reactive species. A subset of observations targeted the N2O5 molecule by detecting the additional NO3 formed by the thermal dissociation of N2O5. In all cases the concentrations of the atmospheric absorbers were retrieved by fitting the differential structure in the broadband cavity ringdown spectra using a methodology adapted from long path differential optical absorption spectroscopy. The uncertainty of the retrieval depends crucially on the correct treatment and fitting of the absorption bands due to water vapour, a topic that is discussed in the context of analysing broadband cavity ringdown spectra. The quality of the measurements and the retrieval method are illustrated with representative spectra acquired during NAMBLEX in spectral regions around 660 nm (NO3 and N2O5) and 570 nm (I2 and OIO). Typical detection limits were 1 pptv for NO3 in an integration time of 100 s, 4 pptv for OIO and 20 pptv for I2 in an integration time of 10 min. Additionally, the concentrations of atmospheric water vapour and the aerosol optical extinction were retrieved in both spectral regions. A companion paper in this issue presents the time series of the measurements and discusses their significance for understanding the variability of short lived nitrogen and iodine compounds in the marine boundary layer.

scholarly journals Effects of Large Eddies on the Structure of the Marine Boundary Layer under Strong Wind Conditions

2004 ◽  
Vol 61 (24) ◽  
pp. 3049-3064 ◽  
Author(s):  
Isaac Ginis ◽  
Alexander P. Khain ◽  
Elena Morozovsky
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Marine Boundary Layer ◽  
Sea Surface ◽  
Cloud Formation ◽  
Strong Wind ◽  
Latent Heat Release ◽  
Air Humidity ◽  
Near Surface ◽  
Large Eddies

Abstract A model of the atmospheric boundary layer (BL) is presented that explicitly calculates a two-way interaction of the background flow and convective motions. The model is utilized for investigation of the formation of large eddies (roll vortices) and their effects on the structure of the marine boundary layer under conditions resembling those of tropical cyclones. It is shown that two main factors controlling the formation of large eddies are the magnitude of the background wind speed and air humidity, determining the cloud formation and latent heat release. When the wind speed is high enough, a strong vertical wind shear develops in the lower part of the BL, which triggers turbulent mixing and the formation of a mixed layer. As a result, the vertical profiles of velocity, potential temperature, and mixing ratio in the background flow are modified to allow for the development of large eddies via dynamic instability. Latent heat release in clouds was found to be the major energy source of large eddies. The cloud formation depends on the magnitude of air humidity. The most important manifestation of the effects of large eddies is a significant increase of the near-surface wind speed and evaporation from the sea surface. For strong wind conditions, the increase of the near-surface speed can exceed 10 m s−1 and evaporation from the sea surface can double. These results demonstrate an important role large eddies play in the formation of BL structure in high wind speeds. Inclusion of these effects in the BL parameterizations of tropical cyclone models may potentially lead to substantial improvements in the prediction of storm intensity.

scholarly journals Iodine-mediated coastal particle formation: an overview of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) Roscoff coastal study

2010 ◽  
Vol 10 (6) ◽  
pp. 2975-2999 ◽  
Author(s):  
G. McFiggans ◽  
C. S. E. Bale ◽  
S. M. Ball ◽  
J. M. Beames ◽  
W. J. Bloss ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ultrafine Particles ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Measurement Techniques ◽  
Ultrafine Particle ◽  
Molecular Iodine ◽  
Particle Formation ◽  
North West ◽  
Iodine Species

Abstract. This paper presents a summary of the measurements made during the heavily-instrumented Reactive Halogens in the Marine Boundary Layer (RHaMBLe) coastal study in Roscoff on the North West coast of France throughout September 2006. It was clearly demonstrated that iodine-mediated coastal particle formation occurs, driven by daytime low tide emission of molecular iodine, I2, by macroalgal species fully or partially exposed by the receding waterline. Ultrafine particle concentrations strongly correlate with the rapidly recycled reactive iodine species, IO, produced at high concentrations following photolysis of I2. The heterogeneous macroalgal I2 sources lead to variable relative concentrations of iodine species observed by path-integrated and in situ measurement techniques. Apparent particle emission fluxes were associated with an enhanced apparent depositional flux of ozone, consistent with both a direct O3 deposition to macroalgae and involvement of O3 in iodine photochemistry and subsequent particle formation below the measurement height. The magnitude of the particle formation events was observed to be greatest at the lowest tides with the highest concentrations of ultrafine particles growing to the largest sizes, probably by the condensation of anthropogenically-formed condensable material. At such sizes the particles should be able to act as cloud condensation nuclei at reasonable atmospheric supersaturations.

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