scholarly journals Effects of Sea Salt Aerosol Emissions for Marine Cloud Brightening on Atmospheric Chemistry: Implications for Radiative Forcing

2020 ◽  
Vol 47 (4) ◽  
Author(s):  
Hannah M. Horowitz ◽  
Christopher Holmes ◽  
Alicia Wright ◽  
Tomás Sherwen ◽  
Xuan Wang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Sea Salt ◽  
Sea Salt Aerosol ◽  
Aerosol Emissions

Exploring ice core sea ice proxies through process-based modelling

2020 ◽  
Author(s):  
Rachael Rhodes ◽  
Xin Yang ◽  
Eric Wolff
Keyword(s):  
Sea Ice ◽  
Atmospheric Chemistry ◽  
Ice Core ◽  
Ice Cores ◽  
Sea Salt ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Sea Salt Aerosol ◽  
Aerosol Emission ◽  
The Impact

<p>It is important to understand the magnitude and rate of past sea ice changes, as well as their timing relative to abrupt shifts in other components of Earth’s climate system. Furthermore, records of past sea ice over the last few centuries are urgently needed to assess the scale of natural (internal) variability over decadal timescales. By continuously recording past atmospheric composition, polar ice cores have the potential to document changing sea ice conditions if atmospheric chemistry is altered.  Sea salt aerosol, specifically sodium (Na), and bromine enrichment (Br<sub>enr</sub>, Br/Na enriched relative to seawater ratio) are two ice core sea ice proxies suggested following this premise.</p><p>Here we aim to move beyond a conceptual understanding of the controls on Na and Br<sub>enr</sub> in ice cores by using process-based modelling to test hypotheses. We present results of experiments using a 3D global chemical transport model (p-TOMCAT) that represents marine aerosol emission, transport and deposition. Critically, the complex atmospheric chemistry of bromine is also included. Three fundamental issues will be examined: 1) the partitioning of Br between gas and aerosol phases, 2) sea salt aerosol production from first-year versus multi-year sea ice, and 3) the impact of increased acidity in the atmosphere due to human activity in the Arctic.</p>

scholarly journals Modelling sea salt aerosol and its direct and indirect effects on climate

2007 ◽  
Vol 7 (5) ◽  
pp. 14939-14987 ◽  
Author(s):  
X. Ma ◽  
K. von Salzen ◽  
J. Li
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Sea Salt ◽  
Size Distributions ◽  
Size Dependent ◽  
Sea Salt Aerosol ◽  
Direct Forcing ◽  
Log Normal

Abstract. A size-dependent sea salt aerosol parameterization was developed based on the piecewise log-normal approximation (PLA) for aerosol size distributions. Results of this parameterization from simulations with a global climate model produce good agreement with observations at the surface and for vertically-integrated volume size distributions. The global and annual mean of the sea salt burden is 10.1 mg m−2. The direct radiative forcing is calculated to be −1.52 and −0.60 W m−2 for clear sky and all sky, respectively. The first indirect radiative forcing is about twice as large as the direct forcing for all-sky (−1.34 W m−2). The results also show that the total indirect forcing of sea salt is −2.9 W m−2 if climatic feedbacks are taken into account. The sensitivity of the forcings to changes in the burdens and sizes of sea salt particles was also investigated based on additional simulations with a different sea salt source function.

scholarly journals The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance in the Arctic

2010 ◽  
Vol 10 (11) ◽  
pp. 28859-28908 ◽  
Author(s):  
H. Struthers ◽  
A. M. L. Ekman ◽  
P. Glantz ◽  
T. Iversen ◽  
A. Kirkevåg ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Salt ◽  
The Arctic ◽  
Polar Cap ◽  
Sea Ice Extent ◽  
Arctic Clouds ◽  
Radiative Balance ◽  
Sea Salt Aerosol ◽  
Aerosol Emissions ◽  
Natural Aerosol

Abstract. Understanding Arctic climate change requires knowledge of both the external and the local drivers of Arctic climate as well as local feedbacks within the system. An Arctic feedback mechanism relating changes in sea ice extent to an alteration of the emission of sea salt aerosol and the consequent change in radiative balance is examined. A set of idealized climate model simulations were performed to quantify the radiative effects of changes in sea salt aerosol emissions induced by prescribed changes in sea ice extent. The model was forced using sea ice concentrations consistent with present day conditions and projections of sea ice extent for 2100. Sea salt aerosol emissions increase in response to a decrease in sea ice, the model results showing an annual average increase in number emission over the polar cap (70–90° N) of 86×106 m−2 s−1 (mass emission increase of 23 μg m−2 s−1). This in turn leads to an increase in the natural aerosol optical depth of approximately 23%. In response to changes in aerosol optical depth, the natural component of the aerosol direct forcing over the Arctic polar cap is estimated to be between −0.2 and −0.4 W m−2 for the summer months, which results in a negative feedback on the system. The model predicts that the change in first indirect aerosol effect (cloud albedo effect) is approximately a factor of ten greater than the change in direct aerosol forcing although this result is highly uncertain due to the crude representation of Arctic clouds and aerosol-cloud interactions in the model. This study shows that both the natural aerosol direct and first indirect effects are strongly dependent on the surface albedo, highlighting the strong coupling between sea ice, aerosols, Arctic clouds and their radiative effects.

scholarly journals Effect of sea-salt aerosol on tropospheric bromine chemistry

2018 ◽  
Author(s):  
Lei Zhu ◽  
Daniel J. Jacob ◽  
Sebastian D. Eastham ◽  
Melissa P. Sulprizio ◽  
Xuan Wang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Sea Salt ◽  
Heterogeneous Reactions ◽  
Tropospheric Chemistry ◽  
Sulfur Species ◽  
Sea Salt Aerosol ◽  
Volatile Organic ◽  
First Time

Abstract. Bromine radicals influence global tropospheric chemistry by depleting ozone and OH, and by oxidizing elemental mercury, sulfur species, and volatile organic compounds. Observations typically indicate a 50 % depletion of sea salt aerosol (SSA) bromide relative to seawater composition, implying that SSA debromination could be the dominant global source of tropospheric bromine. However, it has been difficult to reconcile this large source with the relatively low BrO concentrations observed in the marine boundary layer (MBL). Here we present a new mechanistic description of SSA debromination in the GEOS-Chem global atmospheric chemistry model with a detailed representation of halogen (Cl, Br, and I) chemistry. We show, for the first time, observed levels of SSA debromination can be reproduced in a manner consistent with observed BrO concentrations. Bromine radical sinks from the HOBr + S(IV) heterogeneous reactions and from ocean emission of acetaldehyde are found to be critical in moderating tropospheric BrO levels. The resulting HBr is rapidly taken up by SSA and also deposited. We find that the source of bromine radicals is mostly from SSA in the MBL, but from organobromines in the free troposphere. Simulated BrO in the MBL is generally much higher in winter than in summer due to a combination of greater SSA emission and weaker radiation. Outstanding issues are the model underestimate of free tropospheric BrO, driven by the HOBr + S(IV) reactions, and uncertainty regarding HBr uptake by SSA.

scholarly journals Sea ice as a source of sea salt aerosol to Greenland ice cores: a model-based study

2017 ◽  
Vol 17 (15) ◽  
pp. 9417-9433 ◽  
Author(s):  
Rachael H. Rhodes ◽  
Xin Yang ◽  
Eric W. Wolff ◽  
Joseph R. McConnell ◽  
Markus M. Frey
Keyword(s):  
Sea Ice ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Ice Core ◽  
Ice Cores ◽  
Open Ocean ◽  
Sea Salt ◽  
The Arctic ◽  
Sea Salt Aerosol ◽  
Annual Variability

Abstract. Growing evidence suggests that the sea ice surface is an important source of sea salt aerosol and this has significant implications for polar climate and atmospheric chemistry. It also suggests the potential to use ice core sea salt records as proxies for past sea ice extent. To explore this possibility in the Arctic region, we use a chemical transport model to track the emission, transport, and deposition of sea salt from both the open ocean and the sea ice, allowing us to assess the relative importance of each. Our results confirm the importance of sea ice sea salt (SISS) to the winter Arctic aerosol burden. For the first time, we explicitly simulate the sea salt concentrations of Greenland snow, achieving values within a factor of two of Greenland ice core records. Our simulations suggest that SISS contributes to the winter maxima in sea salt characteristic of ice cores across Greenland. However, a north–south gradient in the contribution of SISS relative to open-ocean sea salt (OOSS) exists across Greenland, with 50 % of winter sea salt being SISS at northern sites such as NEEM (77° N), while only 10 % of winter sea salt is SISS at southern locations such as ACT10C (66° N). Our model shows some skill at reproducing the inter-annual variability in sea salt concentrations for 1991–1999, particularly at Summit where up to 62 % of the variability is explained. Future work will involve constraining what is driving this inter-annual variability and operating the model under different palaeoclimatic conditions.

scholarly journals Impact of reactive bromine chemistry in the troposphere

2004 ◽  
Vol 4 (11/12) ◽  
pp. 2481-2497 ◽  
Author(s):  
R. von Glasow ◽  
R. von Kuhlmann ◽  
M. G. Lawrence ◽  
U. Platt ◽  
P. J. Crutzen
Keyword(s):  
Atmospheric Chemistry ◽  
Dimethyl Sulfide ◽  
Marine Boundary Layer ◽  
Transport Model ◽  
Sea Salt ◽  
Chemistry Transport Model ◽  
Bromine Oxide ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Field Campaigns

Abstract. Recently several field campaigns and satellite observations have found strong indications for the presence of bromine oxide (BrO) in the free troposphere. Using a global atmospheric chemistry transport model we show that BrO mixing ratios of a few tenths to 2 pmol mol-1 lead to a reduction in the zonal mean O3 mixing ratio of up to 18% in widespread areas and regionally up to 40% compared to a model run without bromine chemistry. A lower limit approach for the marine boundary layer, that does not explicitly include the release of halogens from sea salt aerosol, shows that for dimethyl sulfide (DMS) the effect is even larger, with up to 60% reduction of its tropospheric column. This is accompanied by dramatic changes in DMS oxidation pathways, reducing its cooling effect on climate. In addition there are changes in the HO2:OH ratio that also affect NOx and PAN. These results imply that potentially significant strong sinks for O3 and DMS have so far been ignored in many studies of the chemistry of the troposphere.

scholarly journals Modelling sea salt aerosol and its direct and indirect effects on climate

2008 ◽  
Vol 8 (5) ◽  
pp. 1311-1327 ◽  
Author(s):  
X. Ma ◽  
K. von Salzen ◽  
J. Li
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Sea Salt ◽  
Size Distributions ◽  
Size Dependent ◽  
Sea Salt Aerosol ◽  
Direct Forcing ◽  
Log Normal

Abstract. A size-dependent sea salt aerosol parameterization was developed based on the piecewise log-normal approximation (PLA) for aerosol size distributions. Results of this parameterization from simulations with a global climate model produce good agreement with observations at the surface and for vertically-integrated volume size distributions. The global and annual mean of the sea salt burden is 10.1 mg m−2. The direct radiative forcing is calculated to be −1.52 and −0.60 W m−2 for clear sky and all sky, respectively. The first indirect radiative forcing is about twice as large as the direct forcing for all-sky (−1.34 W m−2). The results also show that the total indirect forcing of sea salt is −2.9 W m−2 if climatic feedbacks are taken into account. The sensitivity of the forcings to changes in the burdens and sizes of sea salt particles was also investigated based on additional simulations with a different sea salt source function.

scholarly journals The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance in the Arctic

2011 ◽  
Vol 11 (7) ◽  
pp. 3459-3477 ◽  
Author(s):  
H. Struthers ◽  
A. M. L. Ekman ◽  
P. Glantz ◽  
T. Iversen ◽  
A. Kirkevåg ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Salt ◽  
The Arctic ◽  
Polar Cap ◽  
Sea Ice Extent ◽  
Arctic Clouds ◽  
Radiative Balance ◽  
Sea Salt Aerosol ◽  
Aerosol Emissions ◽  
Natural Aerosol

Abstract. Understanding Arctic climate change requires knowledge of both the external and the local drivers of Arctic climate as well as local feedbacks within the system. An Arctic feedback mechanism relating changes in sea ice extent to an alteration of the emission of sea salt aerosol and the consequent change in radiative balance is examined. A set of idealized climate model simulations were performed to quantify the radiative effects of changes in sea salt aerosol emissions induced by prescribed changes in sea ice extent. The model was forced using sea ice concentrations consistent with present day conditions and projections of sea ice extent for 2100. Sea salt aerosol emissions increase in response to a decrease in sea ice, the model results showing an annual average increase in number emission over the polar cap (70–90° N) of 86 × 106 m−2 s−1 (mass emission increase of 23 μg m−2 s−1). This in turn leads to an increase in the natural aerosol optical depth of approximately 23%. In response to changes in aerosol optical depth, the natural component of the aerosol direct forcing over the Arctic polar cap is estimated to be between −0.2 and −0.4 W m−2 for the summer months, which results in a negative feedback on the system. The model predicts that the change in first indirect aerosol effect (cloud albedo effect) is approximately a factor of ten greater than the change in direct aerosol forcing although this result is highly uncertain due to the crude representation of Arctic clouds and aerosol-cloud interactions in the model. This study shows that both the natural aerosol direct and first indirect effects are strongly dependent on the surface albedo, highlighting the strong coupling between sea ice, aerosols, Arctic clouds and their radiative effects.

scholarly journals Sea ice as a source of sea salt aerosol to Greenland ice cores: a model-based study

2017 ◽  
Author(s):  
Rachael H. Rhodes ◽  
Xin Yang ◽  
Eric W. Wolff ◽  
Joseph R. McConnell ◽  
Markus M. Frey
Keyword(s):  
Sea Ice ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Ice Core ◽  
Ice Cores ◽  
Open Ocean ◽  
Sea Salt ◽  
The Arctic ◽  
Sea Salt Aerosol ◽  
Annual Variability

Abstract. Growing evidence suggests that the sea ice surface is an important source of sea salt aerosol and this has significant implications for polar climate and atmospheric chemistry. It also offers the opportunity to use ice core sea salt records as proxies for past sea ice extent. To explore this possibility in the Arctic region, we use a chemical transport model to track the emission, transport and deposition of sea salt from both the open ocean and the sea ice, allowing us to assess the relative importance of each. Our results confirm the importance of sea ice sea salt (SISS) to the winter Arctic aerosol burden. For the first time, we explicitly simulate the sea salt concentrations of Greenland snow and find they match high resolution Greenland ice core records to within a factor of two. Our simulations suggest that SISS contributes to the winter maxima in sea salt characteristic of ice cores across Greenland. A north-south gradient in the contribution of SISS relative to open ocean sea salt (OOSS) exists across Greenland, with 50 % of sea salt being SISS at northern sites such as NEEM, while only 10 % of sea salt is SISS at southern locations such as ACT10C. Our model shows some skill at reproducing the inter-annual variability in sea salt concentrations for 1991–1999 AD, particularly at Summit where up to 62 % of the variability is explained. Future work will involve constraining what is driving this inter-annual variability and operating the model under different paleoclimatic conditions.

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