Although aerosols in the Arctic have multiple and complex impacts on the regional climate, their removal due to deposition is still not well quantified. We combined meteorological, aerosol, precipitation, and snowpack observations with simulations to derive information about the deposition of sea salt components and black carbon (BC) from November 2011 to April 2012 to the Arctic snowpack at two locations close to Ny-Ålesund, Svalbard. The dominating role of sea salt and the contribution of dust for the composition of atmospheric aerosols were reflected in the seasonal composition of the snowpack. The strong alignment of the concentrations of the major sea salt components in the aerosols, the precipitation, and the snowpack is linked to the importance of wet deposition for transfer from the atmosphere to the snowpack. This agreement was less strong for monthly snow budgets and deposition, indicating important relocation of the impurities inside the snowpack after deposition. Wet deposition was less important for the transfer of nitrate, non-sea-salt sulfate, and BC to the snow during the winter period. The average BC concentration in the snowpack remains small, with a limited impact on snow albedo and melting. Nevertheless, the observations also indicate an important redistribution of BC in the snowpack, leading to layers with enhanced concentrations. The complex behavior of bromide due to modifications during sea salt aerosol formation and remobilization in the atmosphere and in the snow were not resolved because of the lack of bromide measurements in aerosols and precipitation.
Aerosols and specifically black carbon (BC) play an important role in the regional climate of the Arctic (Shindell, 2007; Quinn et al., 2007) since they modify the radiation balance of the atmosphere, as well as the activation of clouds, and reduce the albedo of different cryospheric components like snow and glaciers, enhancing the melting of snow and ice after deposition. Arctic aerosols exhibit a pronounced seasonal cycle with high concentrations in winter and early spring and lower values in summer (Law and Stohl, 2007; Quinn et al., 2007; Eleftheriadis et al., 2009). This seasonality is caused by different processes related to emission, transport, and deposition, which undergo seasonal cycles (Law and Stohl, 2007; Croft et al., 2016).
Sea spray, dust, and biogenic aerosol particles are important natural aerosol types in the Arctic. In contrast, Arctic BC stems primarily from regions outside the Arctic (Law and Stohl, 2007). Like in all marine environments, sea salt aerosol (SSA) dominates the atmospheric aerosol burden over the Arctic Ocean and its coastal areas (e.g., Geng et al., 2010; Weinbruch et al., 2012). The production and climatic effects of SSA in the Arctic are expected to change in the future as a result of changes in the sea ice cover and ocean temperatures (Struthers et al., 2011; Zábori et al., 2013). Dust may act as effective ice nuclei in the Arctic (Si et al., 2018) and may have the potential to influence radiative and other properties of mixed-phase cold clouds.
Removal due to deposition controls the lifetime of aerosols and in the Arctic determines the input of aerosols to the snow and glaciers. In fact, past atmospheric input has been reconstructed from ice cores in the Arctic (Legrand and Mayewski, 1997; Isaksson et al., 2003; Bauer et al., 2013). Moreover, the deposition of BC to cryospheric components like snow and sea ice also impacts the local and regional climate in the Arctic due to the lowering of the snow albedo and associated albedo feedback processes (e.g., Flanner et al., 2007; Bond et al., 2013; Jacobi et al., 2015). The removal is a result of wet deposition caused by precipitation and dry deposition of particles, which depend on aerosol size, meteorological conditions, and properties of the atmospheric boundary layer. Despite its importance, the deposition of aerosols to the cryosphere is not well quantified for many polar sites, and even the respective contributions of wet and dry deposition are not well known for many compounds (Legrand and Mayewski, 1997; Bauer et al., 2013). Moreover, Stohl et al. (2007) evoked a potentially large enhancement of the deposition of impurities due to blowing snow during a period with elevated aerosol concentrations.
The recommended method to determine dry deposition relies mostly on the
calculation of fluxes based on atmospheric composition and an estimated dry
deposition velocity (Vet et al., 2014), which shows a large
uncertainty. In the case of BC, the calculated deposition varies
considerably across models since it depends on the applied assumptions and
parameters concerning the size of the aerosols and the mixing state (Bond et
al., 2013). For example, the estimated total BC deposition in the Arctic
varies between 8 and more than 13 Tg C yr
While detailed investigations of the chemical properties of aerosols have been performed at Ny-Ålesund based on single-particle analysis (e.g., Geng et al., 2010; Weinbruch et al., 2012), similar studies for the composition of precipitation and the snowpack are currently missing. Moreover, due to the rapid changes in aerosol sources it is urgent to better quantify the fate of different aerosol types in the Arctic. Here, we combine observations in the snowpack and the atmosphere to better constrain deposition processes for major and minor sea salt components and BC around Ny-Ålesund, Svalbard, during the winter period. We used meteorological observations to perform detailed physical snowpack modeling. The results of such simulations are to our knowledge for the first time combined with precipitation and atmospheric aerosol measurements to derive chemical profiles and monthly snow budgets related to dry and wet deposition. The calculated profiles are finally compared to physical and chemical snowpack measurements to evaluate the performance of the snowpack model and to improve our understanding of the deposition processes. Variations in the concentrations of multiple species in aerosols, precipitation, and in the snowpack are used to study the transfer processes from the atmosphere to the snow for the investigated species.
Sampling of snow was performed in snow pits on two glaciers located
approximately 8 and 35 km to the east of Ny-Ålesund, Svalbard (Fig. 1).
The snow was sampled on 30 March 2012 on the Kongsvegen glacier (snow pit
KV; 78.755
A 3-D map of the Kongsfjord area with Ny-Ålesund (red), Zeppelin Station (green), and the locations of the snow pits on the Kongsvegen (light blue) and Austre Lovénbreen glaciers (dark blue) indicated (adapted from ©Norwegian Polar Institute).
All samples were stored at
Refractory BC (rBC) was determined with a single-particle soot photometer (SP2, Droplet Measurement Technologies, USA). Details of the analytical procedure are described in Lim et al. (2014). Briefly, the SP2 allows for quantifying the mass of single particles using a laser-induced incandescence technique. The instrument has unity detection efficiency for rBC particles with diameters between 80 and 600 nm, while avoiding interferences with other inorganic or organic species. The instrument was calibrated using size-selected fullerene soot (Alfa Aesar Inc., USA). A commercial nebulizer (APEX-Q, Elemental Scientific Inc., Omaha, USA) was used to transfer the particles from the melted snow to the aerosol phase. The losses during aerosolization were determined daily using suspensions of Aquadag standards with different mass concentrations, resulting in an average efficiency of 56 %, which was applied to all reported rBC concentrations. Further details are shown in the Supplement (Fig. S1). Two samples from snow pit AL showed rBC concentrations below the limit of quantification of 0.03 ppb (Lim et al., 2014), which was used instead for all further calculations.
Meteorological parameters were recorded close to the analyzed snow pit KV by
an energy balance station (Karner et al., 2013). The station provided data
on air temperature, relative humidity, wind speed, wind direction, and shortwave and longwave radiation components. Surface height changes were
recorded with an ultrasonic ranger and allowed for deriving accumulation rates.
Temperature-corrected raw data were retained for changes of more than 1 cm h
Simulations for the snowpack on the Kongsvegen glacier were performed with
the one-dimensional multilayer physical snowpack model CROCUS (Vionnet et
al., 2012; Jacobi et al., 2010a, 2015), which was previously applied for
mass-balance simulations of the glacier (Sauter and Obleitner, 2015). The
model solves the surface mass and energy budgets by taking into account
physical processes like heat diffusion, transfer of radiation,
densification, sublimation, condensation, and melting. The model is forced
using meteorological data including air temperature, wind speed, relative
humidity, precipitation rate and phase, incoming direct and diffuse
shortwave radiation, incoming longwave radiation, and cloud cover. The
forcing data for the period September 2011 to March 2012 were generated from
observations at the energy balance station KNG8. The model was initiated
with an ice layer set to a temperature of 0
We estimate an overall uncertainty of 21 % for the snow budgets due to error propagation from the combination of the spatial variability of 20 % (Svensson et al., 2013), analytical error of 5 % (2.2), and error of the density measurements of 6 % (Proksch et al., 2016). As a result all calculated (total and monthly) budgets differing by less than 21 % are not considered to be significantly different.
Atmospheric concentrations
Dry deposition of particles (
Wet deposition (
Major sea salt components and nitrate were determined using ion
chromatography in precipitation samples collected on a weekly basis using a
bucket funnel system in summer and a snow sampler in winter (Kühnel et
al., 2011; Aas et al., 2013). The data downloaded from the EBAS database
(ebas.nilu.no) were used without further correction, although the bulk
sampler likely also collected gaseous compounds and particulate material due
to dry deposition. Especially in periods with high wind speed, the bulk
collector may also catch large sea spray aerosols. However, the exact
contribution of dry deposition to the wet deposition calculated here is
difficult to quantify since it depends on the frequency of rain events and
episodes with elevated sea salt aerosols. The total and monthly wet
deposition was calculated as the sum for the period 31 October 2011 to
1 April 2012 and for each month (except October). No measurements of bromide
and BC in the precipitation are available. For bromide, wet deposition was
estimated from the wet deposition of sodium, also by applying standard seawater
ratios. Wet deposition of BC was estimated according to the scavenging
scheme proposed by Sharma et al. (2013). The change in atmospheric BC
concentration
We used a scavenging coefficient of
Since typical top heights of clouds in the wintertime Arctic are on the
order of 4500 m (Intrieri et al., 2002) we used
The stratigraphy and densities for the two analyzed snow pits are shown in
Fig. 2. The investigated snow layers comprised depths down to
Snow stratigraphy observed in the snow pits KV
Together with the stratigraphy, full snow density profiles were established for both pits as shown in Fig. 2. According to these profiles, the total accumulation amounts to 943 and 667 mm of snow water equivalent (SWE) for the snow pits KV and AL. The accumulation in the pit KV was close to the maximum observed in the years 2007 to 2009 at altitudes above 600 m on the Kongsvegen glacier (Forsström et al., 2013). The observed accumulation of precipitation at Ny-Ålesund close to sea level corresponds to a value of 278 mm for the period 31 October 2011 to 1 April 2012. The gradient in accumulation between the snow pits KV, AL, and Ny-Ålesund was slightly higher than 30 % per 100 m of altitude increase and is thus close to the accumulation gradients previously applied for the nearby Midre Lovénbreen and Austre Brøggerbreen glaciers (Hodson et al., 2005).
CROCUS model results obtained for the snow pit KV were used here for further
analysis. The snowpack simulated for 29 March 2012 consists of 50 layers
with varying densities covering a total depth of
Colocated impurity profiles were established for each measured compound
by combining the measured concentrations with either the observed stratigraphy
for both snow pits or the simulated stratigraphy for snow pit KV. Profiles
were established by assuming homogeneous concentrations for the identified
snow layers and by adjusting the closest observed concentrations to the
vertical extent of the observed or simulated layers. Figure 3 shows
the observed sodium and rBC concentrations as well as the profiles.
Some common features can be identified for sodium in the upper part of both
snow pits. Snow pit KV showed three layers with elevated concentrations: a
first peak in the March layer around
The lowest concentrations of all studied impurities were found for rBC.
Average rBC concentrations differed by a factor of 2 between the two
locations, with 0.6 ppb at KV (Fig. 3c) and 1.2 ppb at AL (Fig. 3d). The
average concentration at AL is in good agreement with the average rBC
concentration of (
Sodium
Total snow budgets of all measured compounds for the two snow pits were calculated using three different approaches. (i) Simple budgets were determined by multiplying the average concentrations by the total SWE. (ii) Adjusted budgets were calculated from the interpolated density profile shown in Fig. 2 and colocated concentration profiles like in Fig. 3. (iii) For snow pit KV, simulated budgets were obtained by combining the simulated density profiles with simulated concentration profiles. All calculated budgets are summarized in Fig. 4, which also shows the observed wet deposition at Ny-Ålesund and the estimated total dry aerosol deposition for the period 31 October 2011 to 29 March 2012. According to the meteorological records of the Norwegian Meteorological Service (eklima.met.no), no further precipitation occurred between 29 March and 15 April 2012, and the total wet deposition can thus be compared to the budget of the snow pit AL.
Snow budgets of sea salt components, nss sulfate, nitrate,
bromide
Due to differences smaller than 21 % in their budgets, it can be assumed that differences for chloride, sodium, magnesium, calcium, and potassium are not significant. The spatial variability of snow concentrations at a scale of meters can be even larger (e.g., Svensson et al., 2013). Thus, the total snow budgets for the pits KV and AL reveal a consistent picture for the sea salt components chloride, sodium, magnesium, potassium, and bromide (Fig. 4), with insignificant differences in the observed total budgets despite differences in altitude and accumulation. This is consistent with recent observations revealing characteristic patterns of aerosol concentrations along Svalbard glaciers, including the Kongsvegen, demonstrating consistent formation, transport, and exchange processes between the atmosphere and the snow (Spolaor et al., 2017).
If post-depositional processes are negligible, the total snow budgets of the impurities correspond to the input due to the sum of wet and dry deposition. Based on the comparison of the total snow budgets with the observed wet deposition, the estimated dry deposition is evaluated for the different impurities. The total snow budgets of chloride, sodium, magnesium, and potassium agree well with the observed wet deposition at Ny-Ålesund, with differences smaller than 20 % for the period October 2011 to March–April 2012. However, the recorded wet deposition also includes variable contributions from dry deposition since the precipitation samples were collected with an open bucket instrument (Kühnel et al., 2011). Nevertheless, the estimated dry deposition corresponds to less than 5 % of the wet deposition of chloride, sodium, and magnesium and reaches a maximum of 14 % for potassium (Fig. 4). Subtracting the nss sulfate from the total sulfate shows that the dry deposition of sulfate with marine origin also corresponds to less than 5 % of the total wet deposition. Since the estimated dry deposition is considered to be an upper limit, it can be assumed that its contribution for the total snow budget on the Kongsvegen and Austre Lovénbreen glaciers during the period November 2011 to April 2012 remained small for chloride, sodium, magnesium, potassium, and sea salt sulfate. The estimated wet deposition for bromide based on sodium concentrations and the standard seawater ratio leads to an overestimation of more than 40 % compared to the observed bromide in the snowpack (Fig. 4). This demonstrates that sea salt bromide is undergoing important modifications during the formation of sea salt aerosols in the atmosphere or after deposition (see Sect. 3.7).
Like for the sea salt components, a good agreement between the KV snow
budget of nitrate and nss sulfate and the total deposition during the period
October 2011 to April 2012 is found. For these two compounds the
observed wet deposition at Ny-Ålesund remains significantly below the
snow budget, while the missing fractions are largely compensated for by the
estimated dry deposition. For nitrate, the dry deposition is comparable to
the wet deposition, whereas for nss sulfate, dry deposition even dominates the
snow budget. The adjusted budgets of the snow pit AL show
Regarding the snow budgets, the differences in the rBC profiles and average
concentrations are partly compensated for by the different accumulation for the
two snow pits. The simple, adjusted, and simulated snow budgets vary between
0.51 and 0.71 mg m
The anticorrelation between accumulation and the average BC concentrations
in the two snow pits points to an important contribution of dry deposition,
which is in agreement with the estimated dry and wet deposition of BC. The
dry deposition of eBC (Fig. 4) derived with a deposition velocity of 0.1 cm s
Previous model studies have indicated that BC in the Arctic is primarily removed through wet deposition (e.g., Flanner et al., 2007; Wang et al., 2011). However, in the models the dry deposition velocity of BC was often reduced to improve the simulated atmospheric concentrations of BC. Moreover, the wintertime deposition observed here may not be extrapolated to the entire Arctic since BC deposition depends on multiple factors like air mass transport, aging processes of atmospheric BC particles, and ice nucleation (e.g., Sharma et al., 2013; Liu et al., 2011; Vergara-Temprado et al., 2018)
To derive a higher temporal resolution of the snow budgets, monthly snow budgets were calculated from layers deposited in each month between November 2011 and March 2012. The monthly budgets are further compared to monthly wet and dry deposition. Each weekly wet deposition was attributed to the month with the largest overlap in time to derive the monthly wet deposition, while the monthly dry deposition was calculated from the daily dry deposition. Monthly total deposition was calculated as the sum of the corresponding wet and dry deposition. Figure 5 shows the results for sodium, nitrate, and BC. Results similar to sodium were in general obtained for the other sea salt components. The dominating role of wet deposition for sodium and other sea salt components, as well as the larger contribution of dry deposition for nitrate and BC, is also reflected in the monthly budgets. For the months with recorded precipitation at Ny-Ålesund, the wet deposition of sea salt components largely dominates the total deposition. This is in contrast to nitrate and BC, which show several monthly budgets with higher values for dry than wet deposition.
Monthly accumulation and snow budgets for sodium, nitrate, and BC for the snow pits KV (Kongsvegen, orange) and AL (Austre Lovénbreen, green) according to the simulated profiles. Also shown is the observed accumulation at Ny-Ålesund (top, blue) and the total deposition divided into wet (blue) and dry (red) deposition. For sodium and nitrate the wet deposition was measured at Ny-Ålesund and the wet deposition for BC was estimated from scavenging. The BC snow budgets correspond to rBC, while the wet and dry depositions correspond to eBC.
The generally good agreement between the total budgets of the two snow pits and the wet and dry deposition (Fig. 4) is only partly confirmed by the monthly budgets shown in Fig. 5. For example, the monthly budgets of sodium show a much more pronounced variability at KV compared to AL. In contrast, the monthly total deposition shows a very low value for December due to the lack of wet deposition observed at Ny-Ålesund and no clear cycle for the remaining months. Similar results are obtained for other sea salt components. In general, differences are caused by multiple factors related to uncertainties in the snow model results, the corresponding forcing data, and the spatial variability of the observations in the snow, wet deposition, and aerosol concentrations. Moreover, post-depositional processes modifying the derived monthly snow budgets, like blowing snow or melting processes, are currently not taken into account in the simulations.
Variation diagrams showing the concentrations of two trace compounds are
often exploited to determine common sources or processes acting upon the
correlated species. Here, the ratios of concentrations in the atmosphere,
the precipitation, and the snow are used to study transfer processes
from the atmosphere to the snow. Figure 6 shows the variation of chloride vs.
sodium for the period October 2011 to April 2012 in aerosols at
Zeppelin Station, in the precipitation at Ny-Ålesund, and in the snow
pits KV and AL. Most of the chloride-to-sodium ratios in the aerosols are
close to the standard seawater ratio (Millero et al., 2008), indicating that
in the marine environment around Ny-Ålesund the composition of the
aerosols is dominated by sea salt. Some aerosol samples show dechlorination,
likely caused by the replacement of chlorine ions due to the uptake of
sulfuric and nitric acid (Keene et al., 1998). Figure 6 further demonstrates
that the impact of dechlorination becomes visible only during periods
with low atmospheric loading of sea salt aerosols with less than 1
BC vs. nss sulfate concentrations in snow pits KV (filled diamonds)
and AL (filled squares) and in aerosols (open triangles). The lines
calculated by linear regression with slope
Bromide-to-sodium ratio in the snow pits KV
Calcium shows a different behavior compared to the other major sea salt components, with a significant enrichment of calcium in the aerosols as well as in the precipitation, which results in calcium-to-sodium ratios above standard seawater in a large number of snow samples (Fig. 6). Such an enrichment in the Arctic may be attributed to calcium-rich aerosols originating from soils (Toom-Sauntry and Barrie, 2002; Geng et al., 2010; Jacobi et al., 2012; Weinbruch et al., 2012), although local aerosol formation was probably limited due to the extended snow cover. The in- or below-cloud scavenging of dust particles likely contributed to the transfer of elevated calcium concentrations from the aerosols to the precipitation and to the snow.
As demonstrated in previous studies (e.g., Jacobi et al., 2012), nitrate and nss sulfate in aerosols, precipitation, and snow do not exhibit a constant ratio compared to sodium (Fig. 6). The highest ratios are found in the aerosols and the lowest ratios in the precipitation, with the average snowpack ratio between these values. This confirms that the nitrate and nss sulfate in the snowpack can be attributed to a mixture of wet deposition and dry deposition of aerosols. Although in wintertime the reactive nitrogen budget is dominated by particulate nitrate (Hara et al., 1999), further dry deposition of gas-phase species to the snow is possible, which may be even more important than aerosol deposition (Björkman et al., 2013).
Due to the different sources of BC and sodium (long-range transport vs. local
or regional formation of sea salt aerosols), no consistent BC-to-sodium
variation is found in the aerosols (Fig. S3).
Similarly, the variation of BC in the snow pits is also independent of the
sodium concentrations. Since BC particles are preferentially coated by
organic matter or sulfate (Liu et al., 2011), atmospheric BC shows a
positive relationship to nss sulfate, resulting in a coefficient of
determination
Since no bromide concentrations in the aerosols or in the precipitation are
available, the ratio between bromide and sodium is shown in the form of
profiles for the snow pits KV and AL (Fig. 8). The ratio between the overall
bromide and sodium budgets varies between 0.0045 for KV and 0.005 for AL; it
is thus below the standard seawater ratio of 0.00624 (Millero et al.,
2008). Only distinct layers show enrichments of bromide (Fig. 8). Multiple
photochemical processes occur in the sea ice–snow–atmosphere system of the
Arctic, acting upon the variation between bromide and sodium (Simpson et al.,
2007; Jacobi et al., 2012). On solid surfaces (aerosols, snow, sea ice)
bromide can be transformed into volatile bromine compounds that are released
to the atmosphere and subsequently deposited. Therefore, bromide can be
already depleted in the sea salt aerosols generated over sea ice, which
would cause a wet and dry deposition flux lower than estimated based on the
standard seawater ratio, or it can be diminished in the surface snow after
deposition (Jacobi et al., 2012), explaining the average bromide-to-sodium
ratios below the seawater ratio in both snow pits. Nevertheless, since the
released bromide is subsequently deposited, a snowpack with layers enriched
in bromide is also possible depending on the dominating influence of the
release vs. the additional deposition of bromide (Simpson et al., 2007). This
can also explain the contrasting results found on top of the Holtedahlfonna
glacier, located approximately 40 km to the northeast of Ny-Ålesund, in
April 2012. Spolaor et al. (2013) reported that the snowpack was highly
enriched in bromide, with only a few samples close to the seawater ratio,
potentially caused by the additional deposition of bromide after release
from sea-ice-covered areas of the Arctic Ocean. It is well known that such
activation of bromide mainly occurs in springtime after polar sunrise,
explaining the low bromide budgets in the KV and AL snow pits in the winter
period. Since bromine activation over sea ice also leads to a
significant destruction of tropospheric ozone (Jacobi et al., 2010b), the
ozone record at Zeppelin Station may be used as a proxy for the impact of
bromine-rich air masses at Ny-Ålesund and the surrounding area. The
ozone concentration during the entire period covered by the snow pits
remained above 35 ppbV and dropped to
The chemical composition of aerosols, precipitation, and the snowpack was analyzed for Ny-Ålesund, Svalbard. The results concerning the snow budgets, wet deposition, and the ratios of the different components in the snowpack, precipitation, and aerosols underline the importance of wet deposition for the major sea salt components chloride, sodium, potassium, magnesium, and sulfate during the winter period from October 2011 to March 2012, confirming previous studies (Isaksson et al., 2003; Weinbruch et al., 2012; Geng et al., 2010). The significant contribution of wet deposition is further supported by the estimated maximum of dry deposition. Although the choice of the deposition velocity introduces considerable uncertainty, the estimated dry deposition remains well below 10 % of the total deposition for chloride, sodium, and magnesium, while it contributes more than 20 % to the snow budget of calcium and potassium, probably due to a stronger dust contribution. It is possible that the relatively high overall accumulation, including strong precipitation events in the last week of January, contributed to high input due to wet deposition during winter 2011–2012. Therefore, the contribution of the dry deposition of sea salt aerosols could be larger during winter periods with different precipitation characteristics. Nevertheless, it appears that the wet deposition measurements at Ny-Ålesund can be used to estimate the total wintertime deposition of the major sea salt components in the areas surrounding Ny-Ålesund.
In contrast to the major sea salt components, the dry deposition of nitrate
and nss sulfate was more important than the wet deposition. However, the dry
deposition of the corresponding gas-phase species like
The obtained results for the snow budgets and the deposition of BC indicate a behavior of BC resembling nitrate and nss sulfate. In the wintertime the deposition of BC to the snowpack on the glaciers surrounding Ny-Ålesund appears to be equally driven by dry and wet deposition. However, it is important to note the large uncertainties in the estimated BC deposition, for which direct measurements in the Arctic are needed. Overall, the average rBC concentrations in the wintertime snowpack remained below 1.2 ppb, thus causing a marginal reduction of the snow albedo (e.g., Jacobi et al. 2015). In contrast, post-depositional processes are likely at the origin of snow layers, with rBC concentrations increased by a factor of 3 compared to the average. Such layers may cause a stronger direct and indirect impact on the snow albedo via enhanced metamorphism processes (e.g., Jacobi et al., 2015). Further studies with detailed observations of the vertical BC distribution in the snowpack are required for a better quantification of the climate impact of BC in snow.
Bromide is the sea salt compound showing the strongest variability in the ratio to other major components like sodium, which is related to its high mobility in the sea ice–atmosphere–snow system caused by chemical processes. Systematic measurements of bromide not only in the snowpack, but also in the aerosols, precipitation, and fresh snow, are required to further investigate processes before the formation of the sea salt aerosols, during their transport, or after deposition to the snowpack.
While the annual budgets and estimated deposition for most of the studied species agree well, the results for the monthly budgets obtained with detailed snowpack modeling are less convincing. Further improvements regarding the modeling of the Arctic snowpack are needed to better address physical properties (e.g., the evolution of the snow density) and post-depositional processes acting upon the vertical distribution of impurities in the snowpack. Although the treatment of impurities was recently implemented into the CROCUS snowpack model (Tuzet et al., 2017), the impact of processes modifying the vertical distribution of impurities in the Arctic snowpack like blowing snow, sublimation, and percolation are still not fully considered in most models. The full implementation of post-depositional processes into complex snow models may offer the opportunity to exploit further snowpack and ice core observations for the reconstruction of climate and pollution.
The snowpack scheme CROCUS is integrated into the surface modeling
platform SURFEX developed by Météo France. The SURFEX code is freely
available via
The supplement related to this article is available online at:
HWJ designed and wrote the paper and performed the snow sampling, the simulations, and the analysis. FO provided meteorological data for the simulations, advice during the analysis, and support in writing the paper. SDC contributed to the snow sampling and analysis. PG performed the chemical analysis of the snow samples. KE provided atmospheric BC data. WA provided precipitation data. PG, KE, and WA contributed to the writing of the paper. MZ contributed to the snow sampling, performed the BC analysis of the snow samples, and provided support in writing and designing the paper.
The authors declare that they have no conflict of interest.
The fieldwork and corresponding logistics were supported by the personnel of the AWIPEV station. The KV weather station is operated in cooperation with the Norwegian Polar Institute (Tromsø). The measurements of major inorganic ions in precipitation and aerosols at Ny-Ålesund and Zeppelin are part of national atmospheric monitoring financed by the Norwegian Environment Agency.
This research has been supported by the IPEV (grant no. 1030), the ANR (grants nos. ANR 2011 Blanc SIMI 5-6 021 04 and ANR-14-AORS-0002-01), Campus France (grant no. 31597SM), the Austrian Science Fund (grant no. I 369-B17), the CNRS/INSU (grant no. Chantier Arctique Francais/PARCS), the LabEx OSUG@2020 (grant no. ANR10 LABX56), and the Deutsche Forschungsgemeinschaft (grant no. 268020496 – TRR 172).
This paper was edited by Thorsten Bartels-Rausch and reviewed by two anonymous referees.