scholarly journals Evaluating the impact of blowing-snow sea salt aerosol on springtime BrO and O<sub>3</sub> in the Arctic

2020 ◽  
Vol 20 (12) ◽  
pp. 7335-7358 ◽  
Author(s):  
Jiayue Huang ◽  
Lyatt Jaeglé ◽  
Qianjie Chen ◽  
Becky Alexander ◽  
Tomás Sherwen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Salt ◽  
The Arctic ◽  
Blowing Snow ◽  
Sea Salt Aerosol ◽  
Surface Sites ◽  
Surface Snow ◽  
Ozone Monitoring ◽  
Halogen Activation ◽  
Arctic Surface

Abstract. We use the GEOS-Chem chemical transport model to examine the influence of bromine release from blowing-snow sea salt aerosol (SSA) on springtime bromine activation and O3 depletion events (ODEs) in the Arctic lower troposphere. We evaluate our simulation against observations of tropospheric BrO vertical column densities (VCDtropo) from the GOME-2 (second Global Ozone Monitoring Experiment) and Ozone Monitoring Instrument (OMI) spaceborne instruments for 3 years (2007–2009), as well as against surface observations of O3. We conduct a simulation with blowing-snow SSA emissions from first-year sea ice (FYI; with a surface snow salinity of 0.1 psu) and multi-year sea ice (MYI; with a surface snow salinity of 0.05 psu), assuming a factor of 5 bromide enrichment of surface snow relative to seawater. This simulation captures the magnitude of observed March–April GOME-2 and OMI VCDtropo to within 17 %, as well as their spatiotemporal variability (r=0.76–0.85). Many of the large-scale bromine explosions are successfully reproduced, with the exception of events in May, which are absent or systematically underpredicted in the model. If we assume a lower salinity on MYI (0.01 psu), some of the bromine explosions events observed over MYI are not captured, suggesting that blowing snow over MYI is an important source of bromine activation. We find that the modeled atmospheric deposition onto snow-covered sea ice becomes highly enriched in bromide, increasing from enrichment factors of ∼5 in September–February to 10–60 in May, consistent with composition observations of freshly fallen snow. We propose that this progressive enrichment in deposition could enable blowing-snow-induced halogen activation to propagate into May and might explain our late-spring underestimate in VCDtropo. We estimate that the atmospheric deposition of SSA could increase snow salinity by up to 0.04 psu between February and April, which could be an important source of salinity for surface snow on MYI as well as FYI covered by deep snowpack. Inclusion of halogen release from blowing-snow SSA in our simulations decreases monthly mean Arctic surface O3 by 4–8 ppbv (15 %–30 %) in March and 8–14 ppbv (30 %–40 %) in April. We reproduce a transport event of depleted O3 Arctic air down to 40∘ N observed at many sub-Arctic surface sites in early April 2007. While our simulation captures 25 %–40 % of the ODEs observed at coastal Arctic surface sites, it underestimates the magnitude of many of these events and entirely misses 60 %–75 % of ODEs. This difficulty in reproducing observed surface ODEs could be related to the coarse horizontal resolution of the model, the known biases in simulating Arctic boundary layer exchange processes, the lack of detailed chlorine chemistry, and/or the fact that we did not include direct halogen activation by snowpack chemistry.

scholarly journals Evaluating the impact of blowing snow sea salt aerosol on springtime BrO and O<sub>3</sub> in the Arctic

2020 ◽  
Author(s):  
Jiayue Huang ◽  
Lyatt Jaeglé ◽  
Qianjie Chen ◽  
Becky Alexander ◽  
Tomás Sherwen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Atmospheric Deposition ◽  
Sea Salt ◽  
The Arctic ◽  
Local Source ◽  
Blowing Snow ◽  
Sea Salt Aerosol ◽  
Surface Sites ◽  
Surface Snow ◽  
Arctic Surface

Abstract. We use the GEOS-Chem chemical transport model to examine the influence of bromine release from blowing snow sea salt aerosol (SSA) on springtime bromine activation and O3 depletion events (ODEs) in the Arctic lower troposphere. We evaluate our simulation against observations of tropospheric BrO vertical column densities (VCDtropo) from the GOME-2 and OMI spaceborne instruments for three years (2007–2009), as well as against surface observations of O3. We conduct a simulation with blowing snow SSA emissions from first-year sea ice (FYI, with a surface snow salinity of 0.1 psu) and multi-year sea ice (MYI, with a surface snow salinity of 0.05 psu), assuming a factor of 5 bromide enrichment of surface snow relative to seawater. This simulation captures the magnitude of observed March–April GOME-2 and OMI VCDtropo to within 17 %, as well as their spatiotemporal variability (r = 0.76-0.85). Many of the large-scale bromine explosions are successfully reproduced, with the exception of events in May, which are absent or systematically underpredicted in the model. If we assume a lower salinity on MYI (0.01 psu) some of the bromine explosions events observed over MYI are not captured, suggesting that blowing snow over MYI is an important source of bromine activation. We find that the modeled atmospheric deposition onto snow-covered sea ice becomes highly enriched in bromide, increasing from enrichment factors of ~ 5 in September–February to 10–60 in May, consistent with freshly fallen snow composition observations. We propose that this progressive enrichment in deposition could enable blowing snow-induced halogen activation to propagate into May and might explain our late-spring underestimate in VCDtropo. We estimate that atmospheric deposition of SSA could increase snow salinity by up to 0.04 psu between February and April, which could be an important source of salinity for surface snow on MYI as well as FYI covered by deep snowpack. Inclusion of halogen release from blowing snow SSA in our simulations decreases monthly mean Arctic surface O3 by 4–8 ppbv (15–30 %) in March and 8–14 ppbv (30–40 %) in April. We reproduce a transport event of depleted O3 Arctic air down to 40º N observed at many sub-Arctic surface sites in early April 2007. While our simulation captures a few ODEs observed at coastal Arctic surface sites, it underestimates the magnitude of other events and entirely misses some events. We suggest that inclusion of direct snowpack activation, which is a strong local source of Br radicals in the shallow Arctic boundary layer, could help reconcile the success of our simulation at capturing satellite retrievals of VCDtropo with its difficulty in reproducing local ODEs.

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

&lt;p&gt;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&amp;#8217;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. &amp;#160;Sea salt aerosol, specifically sodium (Na), and bromine enrichment (Br&lt;sub&gt;enr&lt;/sub&gt;, Br/Na enriched relative to seawater ratio) are two ice core sea ice proxies suggested following this premise.&lt;/p&gt;&lt;p&gt;Here we aim to move beyond a conceptual understanding of the controls on Na and Br&lt;sub&gt;enr&lt;/sub&gt; 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.&lt;/p&gt;

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 First direct observation of sea salt aerosol production from blowing snow above sea ice

2019 ◽  
Author(s):  
Markus M. Frey ◽  
Sarah J. Norris ◽  
Ian M. Brooks ◽  
Philip S. Anderson ◽  
Kouichi Nishimura ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Open Ocean ◽  
Weddell Sea ◽  
Sea Salt ◽  
Polar Regions ◽  
Blowing Snow ◽  
Snow Layer ◽  
Sea Salt Aerosol ◽  
Drifting Snow

Abstract. Two consecutive cruises in the Weddell Sea, Antarctica, in winter 2013 provided the first direct observations of sea salt aerosol (SSA) production from blowing snow above sea ice, thereby validating a model hypothesis to account for winter time SSA maxima in polar regions not explained otherwise. Blowing or drifting snow always lead to increases in SSA during and after storms. Observed aerosol gradients suggest that net production of SSA takes place near the top of the blowing or drifting snow layer. The observed relative increase of SSA concentrations with wind speed suggests that on average the corresponding aerosol mass flux during storms was equal or larger above sea ice than above the open ocean, demonstrating the importance of the blowing snow source for SSA in winter and early spring. For the first time it is shown that snow on sea ice is depleted in sulphate relative to sodium with respect to sea water. Similar depletion observed in the aerosol suggests that most sea salt originated from snow on sea ice and not the open ocean or leads, e.g. on average 93 % during the 8 June and 12 August 2013 period. A mass budget calculation shows that sublimation of snow even with low salinity (

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 Using CALIOP to constrain blowing snow emissions of sea salt aerosols over Arctic and Antarctic sea ice

2018 ◽  
Author(s):  
Jiayue Huang ◽  
Lyatt Jaeglé ◽  
Viral Shah
Keyword(s):  
Sea Ice ◽  
Lower Troposphere ◽  
Arctic Sea Ice ◽  
Sea Salt ◽  
Polar Regions ◽  
Blowing Snow ◽  
Sea Salt Aerosols ◽  
Antarctic Sea Ice ◽  
Surface Snow ◽  
Frost Flowers

Abstract. Sea salt aerosols (SSA) produced on sea ice surfaces by blowing snow events or lifting of frost flower crystals have been suggested as important sources of SSA during winter over polar regions. The magnitude and relative contribution of blowing snow and frost flower SSA sources, however, remain uncertain. In this study, we use 2007–2009 aerosol extinction coefficients from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite and the GEOS-Chem global chemical transport model to constrain sources of SSA over Arctic and Antarctic sea ice. CALIOP retrievals show elevated levels of aerosol extinctions (10–20 Mm−1) in the lower troposphere (0–2 km) over polar regions during cold months. The standard GEOS-Chem model underestimates the CALIOP aerosol extinctions by 50–70 %. Adding frost flower emissions of SSA fails to explain the CALIOP observations. With blowing snow SSA emissions, the model captures the overall spatial and seasonal variation of CALIOP aerosol extinctions over the polar regions, but overestimates springtime aerosol extinctions over Arctic sea ice and winter-spring extinctions over Antarctic sea ice. We reduce the surface snow salinity over multi-year sea ice and infer the monthly FYI snow salinity required to minimize the discrepancy between CALIOP extinctions and the GEOS-Chem simulation. The empirically-derived snow salinity shows a decreasing trend in between fall and spring. The optimized blowing snow model with inferred snow salinities generally agrees with CALIOP extinction observations to within 10 % over sea ice, but underestimates aerosol extinctions over the regions where frost flowers are expected to have a large influence. Frost flowers could thus contribute indirectly to SSA production by increasing the local surface snow salinity and, therefore, the SSA production from blowing snow. We carry out a case study of an Arctic blowing snow SSA feature predicted by GEOS-Chem and sampled by CALIOP. Using backtrajectories, we link this feature to a blowing snow event which occurred 2 days earlier over first-year sea ice and was also detected by CALIOP.

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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