Atmospheric Environment 38 (2004) 2819–2829
ARTICLE IN PRESS
AE International – Asia
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doi:10.1016/j.at
Seasonal differences in snow chemistry from thevicinity of Mt. Everest, central Himalayas
Shichang Kanga,b,d,*, Paul A. Mayewskib,c, Dahe Qind, Sharon A. Sneedb,Jiawen Rend, Dongqi Zhange
a Institute of Tibetan Plateau Research, CAS, 18 Shuangqing Road, Beijing 100085, ChinabClimate Change Institute, University of Maine, 303 Bryand Hall, Orono, ME 04469, USA
cDepartment of Earth Sciences, University of Maine, Orono, ME 04469, USAdKey Laboratory of Ice Core and Cold Regions Environment, Cold and Arid Regions Environment and Engineering Research Institute,
CAS, Lanzhou 730000, ChinaeChinese Academy of Meteorological Sciences, Beijing 100081, China
Received 8 September 2003; received in revised form 6 January 2004; accepted 25 February 2004
Abstract
During August and September 1998, fresh snow samples were collected in the East Rongbuk (ER) Glacier on the
northern slope of Mt. Everest over an elevation range 5800–6500m. Three snowpits were sampled in the ER glacier at
an elevation of 6400, 6500, and 6500m in August 1998, May 2000 and October 2002, respectively. Snow chemical data
from fresh snow and snowpit samples from the ER Glacier are shown to be consistent with earlier results reported by
other researchers from the vicinity of Mt. Everest. Among major ions, Ca2+ has the most striking seasonal differences:
non-monsoon snow Ca2+ concentration is one order of magnitude higher than monsoon value. A large seasonal
difference characterizes fresh snow SO42� but does not seem to persist in snowpit samples probably as a consequence of
post-depositional ion elution. Non-monsoon snow Na+, K+ and Cl� are close to two times higher than monsoon snow
for both fresh snow and snowpit samples. Magnesium has distinct seasonal variations in snowpit samples and a four-
fold higher concentration in non-monsoon snow than that in monsoon snow. Seasonal differences in major chemical
composition in snow over the Mt. Everest region provide a definitive indicator for precisely dating ice cores and as a
consequence are essential in reconstructing the history of climate change and atmospheric chemistry in this region.
r 2004 Elsevier Ltd. All rights reserved.
Keywords: Fresh snow; Snowpit; Major ions; Seasonal variations; Mt. Everest region
1. Introduction
Studies of climate change as recorded in ice cores
from/near the Mt. Everest region in the central
Himalayas have increased in recent years (Hou et al.,
2002; Qin et al., 2000, 2002; Thompson et al., 2000;
Kang et al., 2001a, b, 2002a, b; Yao et al., 2002). Dating
accuracy is essential to the reconstruction of ice core
ing author. Tel.: +86-10-6284 9071; fax: +86-10-
ess: [email protected] (S. Kang).
e front matter r 2004 Elsevier Ltd. All rights reserve
mosenv.2004.02.043
climatic records and a primary dating method is the
measurement of seasonal variations in chemical species.
To validate seasonal timing of chemical species it is
necessary to establish input timing.
Due to the severe winter weather and the difficult
logistics encountered in the high regions of the
Himalayas, continuous year round precipitation sam-
pling is rarely accomplished. However, during the last
decade, studies on snow chemistry in the central
Himalayas have been undertaken, in order to evaluate
the impact of anthropogenic pollution on high elevation
remote regions. Up to now, chemical data from fresh
d.
ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 38 (2004) 2819–28292820
snow events are mainly available for two seasons:
monsoon and pre-monsoon seasons from both the
northern and southern slopes of Mt. Everest (Jenkins
et al., 1987; Valsecchi et al., 1999; Marinoni et al., 2001;
Shrestha et al., 2002) and its vicinity, such as Mt.
Xixabangma (B100 km from Everest) (Mayewski, 1986;Kang et al., 2002c), Mt. Cho Oyu (B40 km from
Everest) (Balerna et al., 2003), and Hidden Valley
(Shrestha et al., 1997). Short-term fresh snow and
aerosol chemistry sampling during monsoon and post-
monsoon seasons has shown low pollutant concentra-
tions in the Himalayan atmosphere suggesting these sites
are representative of the remote troposphere (Wake
et al., 1994; Shrestha et al., 1997; Kang et al., 2002c;
Marinoni et al., 2001). Comparisons of fresh snow
chemistry from central Himalayas and investigation of
sources of major ions indicate that variations of snow
chemistry are strongly influenced by the seasonality
other than geographical locations (Marinoni et al., 2001;
Kang et al., 2002c; Balerna et al., 2003).
A recent study of a shallow ice core from Mt.
Xixabangme indicates that spring (pre-monsoon season)
and late summer (monsoon season) are key periods in
seasonal variations in snow chemistry in the region
(Kang et al., 2000). The highest values of ion concentra-
tions in snow occur in spring (Wake et al., 1993; Kang
et al., 2000), resulting from dust deposition during the
peak in the dust-storm activity—mainly April and May
over Asia (Parrington et al., 1983; Gao et al., 1992; Qian
et al., 1997). The lowest values of ion concentrations
occur in late summer (Wake et al., 1994; Kang et al.,
2000), reflecting not only decreased dust deposition
(Wake et al., 1994; Shrestha et al., 1997), but also the
effect of increased precipitation washing out aerosols
(Kang et al., 2002c). This seasonal alternation has been
confirmed by fresh snow chemistry studies from the
vicinity of Everest (Marinoni et al., 2001; Shrestha et al.,
2002; Balerna et al., 2003).
In order to evaluate the dependability of using ice core
records to reconstruct past atmospheric change, some
studies focused on how closely snow chemistry repre-
sents atmospheric chemistry by comparing of chemical
compositions between snow and aerosols (Shrestha et al.,
1997) and between wet, dry and snow deposition
(Valsecchi et al., 1999), suggesting that some chemical
species (e.g. NO3�, Cl�, NH4
+) deposited in snow are
influenced by post-depositional processes such as
absorption and scavenging of gaseous species (HCl,
HNO3, NH3) from the atmosphere. A comparison of
two adjacent ice core records from glacier accumulation
zone and percolation zone, respectively, on the northern
slope of Mt. Everest (Hou et al., 2002) shows that the
overall features of the d18O profiles of the two cores aresimilar, while a significant discrepancy exists for the
ionic profiles of the two cores due to post-depositional
modification processes (e.g. the elution process, chemical
reactions). The dramatically decreased NH4+ and SO4
2�
concentrations in the core from percolation zone could
be caused by the ion elution process that moved most
chemicals away with runoff (Hou et al., 2002).
The meteorological and pluviometric regime of the
Asian continent is mainly controlled by polar air masses
from the Arctic, continental air masses from central
Asia, and maritime air masses from the Pacific and
Indian Oceans (Bryson, 1986). The location of the East
Rongbuk (ER) Glacier on Mt. Everest (27�590N,
86�550E) (Fig. 1) at the boundary of the South Asian
monsoon (Indian monsoon) and the continental climate
of central Asia, combined with the high elevation of the
site (6500m, well above the influence of the boundary
layer), offers a unique opportunity to describe and
understand change in climate and chemistry of the
atmosphere over Asia.
Here we present chemical data from fresh snow
sampled in August and September 1998 and three
snowpits sampled in August 1998, May 2000 and
October 2002 from the ER Glacier (Fig. 1) on the
northern slope of Mt. Everest, and compare our data
with existing results from the region. The main purpose
of the present work is to expand the snow chemistry
database for the high mountain regions of the Hima-
layas, and to expand our knowledge of the spatial and
temporal characteristics of snow chemistry in the Mt.
Everest region. In particular, we focus on the differences
between snow chemistry from monsoon and non-
monsoon seasons and verify the significance of this
seasonal difference as applied to high precision ice core
dating.
2. Methods
During August and September 1998, a total of 39
fresh snow samples were collected on the ER Glacier on
the northern slope of Mt. Everest (27�590N, 86�550E).
Our sampling sites were at nine sites between 5800 and
6500m (Fig. 1). Eight storm events were sampled. For
logistical reasons, not all elevations could be sampled for
each event. Three snowpits in the ER Glacier were
sampled continuously at 5 cm depth interval in August
1998, May 2000 and October 2002, respectively.
Sampling methods for fresh snow and snowpit are the
same as those used by Mayewski (1986), Wake et al.
(1993, 1994) and Kang et al. (2000, 2002c). Extreme care
was taken at all times during sample collection and
handling to assure samples were not contaminated. For
example, non-particulating suits, polyethylene gloves
and masks were worn at all times during sampling. Pre-
washed high-density polyethylene HDPE containers
were used as sample scoops. Field blanks were collected,
filled with ultrapure water in the laboratory, opened
during sample collection and handled as samples.
ARTICLE IN PRESS
Fig. 1. Map of sampling sites for fresh snow and snowpits in the East Rongbuk Glacier on the northern slope of Mt. Everest, central
Himalayas.
S. Kang et al. / Atmospheric Environment 38 (2004) 2819–2829 2821
Samples were kept frozen in the field, during transporta-
tion, and in the laboratory until analysis. All of these
sampling techniques have been demonstrated to mini-
mize or eliminate contamination (Wake et al., 1994).
Analysis of duplicate samples as well as field and
laboratory blanks indicates that sample contamination
during sample collection, transport, and subse-
quent analytical procedures is negligible. Major ion
ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 38 (2004) 2819–28292822
(NO3�, Cl�, SO4
2�, NH4+, Ca2+, Na+, K+ and Mg2+)
concentrations were measured at the Climate Change
Institute, University of Maine, USA, using a Dionex Ion
Chromatograph model DX-500. Detailed methods are
described by Buck et al. (1992) and Wake and Mayewski
(1993).
3. Results and discussions
3.1. Chemical composition of fresh snow samples
The mean composition and standard deviation of all
1998 fresh snow samples and each snowfall event are
given in Tables 1 and 2. We calculated the ion balance
DC (sum of cations—sum of anions) for each sample;
the mean value of DC; �0.03meq l�1 (Table 2), indicatesa balance between major cations and anions for our
fresh snow samples. With respect to the sea-salt ratio
(0.86), the ratios of Na+/Cl� from Mt. Everest fresh
snow are very low, with a mean value of 0.30 (Table 2)
and only one event having a ratio higher than 0.86
(Table 1), indicating that there is a large excess of Cl� in
our samples. This is consistent with results from fresh
snow over the Cho Oyu range (Balerna et al., 2003) and
ice core chemical records from the ER Glacier (Kang
et al., 2002b), but in disagreement with the results from
the southern slope of the Nepal Himalayas (Marinoni
Table 1
Mean chemical composition and standard deviation (7) of fresh snoevent (unit: meq l�1)
Date Na+ NH4+ K+ Mg2+ Ca2+ Cl�
30 Aug 0.25 0.01 0.22 0.33 2.63 0.76
70.37 70.02 70.27 70.18 71.74 70.15
31 Aug 0.15 0.09 0.03 0.12 0.16 0.89
70.14 70.10 70.06 70.06 70.19 70.09
Sep 1 +DL 0.19 +DL 0.15 0.15 0.85
Sep 2 0.10 0.28 +DL 0.12 0.92 0.83
Sep 4 0.08 0.88 +DL 0.31 0.56 1.01
Sep 5 0.51 0.06 0.28 0.44 5.63 1.75
70.28 70.10 70.04 70.14 71.14 70.30
Sep 6 0.51 3.72 0.21 0.44 6.11 1.23
70.35 73.76 70.10 70.27 71.13 70.50
Sep 29 1.70 0.53 0.49 0.29 2.40 1.05
72.01 70.81 70.50 70.11 71.20 70.86
DC=([NH4+]+[Ca2+]+[Na+]+[K+]+[Mg2+])�([NO3
�]+[Cl�]+[SO
et al., 2001; Valsecchi et al., 1999), in which the Na+/
Cl� ratios during the monsoon period are very similar to
the classical sea-salt ratio showing the strong marine
contribution related to the monsoon circulation. The
excess Cl� can be explained assuming an enrichment of
Cl� in the snow due to the scavenging of HCl in the
atmosphere. This is supported by comparison between
ion concentrations in snow and aerosols over the
Hidden Valley (Shrestha et al., 1997) and the southern
slope of Mt. Everest (Shrestha et al., 2002). On the other
hand, Na+ and Cl� may have different sources during
the monsoon season. Kang et al. (2002b) has performed
Empirical Orthogonal Function (EOF) analysis for
major ion concentration of the ER ice core to classify
the chemical species in the ice core. EOF analysis allows
a more robust assessment of the behavior of several
variates and also provides new time-series that represent
their relationships. EOF decomposition provides objec-
tive representations of multivariate data through the
analysis of the covariance structure of its variates (e.g.
Meeker et al., 1995). The results form this analysis
indicate that the EOF2 mainly loaded with K+ and Cl�
representing crustal species from, for example, KCl-rich
deposits transported by summer atmospheric circulation
from local or regional sources. Although the source of
the KCl-rich deposits cannot be specified from our
study, a possible source may be local or regional
(around the north and south of Himalayas) mineral
w from the northern slope of Mt. Everest by individual storm
NO3� SO4
2� DC Na+/Cl� No. of
samples
Elevation
(m a.s.l.)
1.31 1.16 0.23 0.30 8 6300–6500
71.26 70.36 72.03 70.38
0.25 0.44 �1.00 0.16 18 6300–6500
70.14 70.15 70.39 70.14
0.97 0.61 �1.92 1 6500
0.17 0.85 �0.42 0.12 1 6300
0.80 0.55 �0.52 0.08 1 6450
4.56 1.14 �0.53 0.28 3 6300–6450
73.82 70.51 73.29 70.14
5.74 1.57 2.46 0.39 2 6450
70.57 71.07 71.22 70.13
0.46 0.50 2.92 0.93 5 5800–6200
70.47 70.35 73.46 70.70
42�]); DL: detection limit.
ARTICLE IN PRESS
Table 2
Mean major ion concentrations and standard deviation (7) of fresh snow and snowpit samples from the East Rongbuk Glacier on thenorthern slope of Mt. Everest (unit: meq l�1)
Number Sampling Elevation Na+ NH4+ K+ Mg2+ Ca2+ Cl� NO3
� SO42� DC Na+/Cl� Depth
(cm)
No. of
sample
Date (m a.s.l.)
Fresh
snow
August–September
1998
5800–6500 0.41 0.34 0.15 0.23 1.71 1.02 1.14 0.72 �0.03 0.30 39
70.86 71.06 70.26 70.16 72.13 70.45 71.90 70.48 71.64 70.40
Snowpit 1 August 1998 6400 0.71 0.08 0.46 0.49 4.85 1.29 0.18 0.69 4.43 0.35 55 11
71.16 70.10 70.54 70.57 79.02 70.06 70.03 70.35 710.38 70.52
Snowpit 2 May 2000 6500 0.75 1.41 0.29 0.35 8.26 0.90 1.37 0.69 8.11 0.65 125 24
70.98 70.92 70.25 70.48 720.31 70.64 71.39 70.46 720.45 70.37
Snowpit 3 October 2002 6500 0.54 Nd 0.24 0.21 2.79 0.55 1.32 0.80 1.13a 0.81 360 74
70.90 70.35 70.20 75.15 70.69 71.13 70.42 74.69 70.30
DC=([NH4+]+[Ca2+]+[Na+]+[K+]+[Mg2+])�([NO3
�]+[Cl�]+[SO42�]); nd: not determined.
anot included [NH4+].
0
2
4
6
8
10
12
14
16
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
Monsoon Pre-monsoon
Ca2+ SO42-Na+ NO3
- Cl-
38.0
1 East Rongbuk Gl., northern slope of Mt. Everest (5800-6500 m a.s.l., Aug.-Sept. 1998, sample number n=39); Present work2 Gyabrag Gl., northern slope of Mt. Cho Oyu (5671-5730 m a.s.l., Sept. 2000, n=7); Balerna et al., 20033 Dasuopu Gl., northern slope of Mt. Xixabangma (5400-7000 m a.s.l., Aug.-Sept. 1997, n=102); Kang et al., 20024 Khumbu Valley, southern slope of Mt. Everest (5050-6050 m a.s.l., Sept.-Oct. 1998, n=17); Marinoni et al., 20015 Khumbu Valley, southern slope of Mt. Everest (5050 m a.s.l., July-Aug., 1992, n=19); Valsecchi et al., 19996 Hidden Valley, Dhaulagiri peak (5050-5700 m a.s.l., Aug. 1994, n=28); Shrestha et al., 19977 Middle Rongbuk Gl., northern slope of Mt. Everest (5600-7100 m a.s.l., Apr.-May 1986, n=96); Jenkins et al., 19878 Northern slope of Mt. Xixabangma (6300 m a.s.l., May 1984, n=6); Mayewski et al., 19869 Island peak, southern slope of Mt. Everest (5300-6100 m a.s.l., May 1994, n=3); Marinoni et al., 2001
* Data are not available.
* *
Ion
conc
entr
atio
ns (
ueq
L-1)
Fig. 2. Comparison of ion concentrations (meq l�1) between monsoon and pre-monsoon fresh snow samples collected in the vicinity ofMt. Everest, central Himalayas.
S. Kang et al. / Atmospheric Environment 38 (2004) 2819–2829 2823
aerosols (Shrestha et al., 1997; Thompson et al., 2000)
that are deposited mainly during the summer season
which we assume because of their connections to
summer atmospheric circulation (Kang et al., 2002b).
In order to investigate the seasonal differences of
major ion concentrations in fresh snow over the vicinity
of Mt. Everest, all data from recent research in the
region is plotted in Fig. 2, to reveal a comparison
between fresh snow chemistry during monsoon and pre-
monsoon seasons. The fresh snow compositions from
the ER Glacier are in accordance with concentrations of
monsoon fresh snow samples collected on both northern
ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 38 (2004) 2819–28292824
and southern slopes of the region, but far lower than
those from fresh snow in pre-monsoon season (Fig. 2).
In addition, for the entire dataset available in this
region, ion concentrations of pre-monsoon samples are
much higher than those of monsoon ones, especially
Ca2+ and SO42� concentrations (Fig. 2).
Calcium concentrations range between 1.71 and
6.44meq l�1 in monsoon fresh snow, and jump to 12.6–38.0meq l�1 in pre-monsoon fresh snow (Fig. 2). Pre-monsoon Ca2+ concentrations are one order of magni-
tude higher than the monsoon concentrations. Pre-
monsoon fresh snow SO42� concentrations vary from 5.8
to 15.9meq l�1, one to two orders of magnitude higherthan monsoon values (0.25–1.38 meq l�1) (Fig. 2).Differences in NO3
� between pre-monsoon and monsoon
season are apparent but not as much as those for Ca2+
and SO42�. Pre-monsoon Na+ and Cl� concentrations in
fresh snow are roughly double higher than those during
monsoon season (Fig. 2). Pre-monsoon NH4+, K+ and
Mg2+ concentrations, available only from one report
(Island Peak, southern slope of Mt. Everest (Marinoni
et al., 2001)), are also higher than those in monsoon
samples, and differences in the three species between two
seasons are similar to those of Na+ and Cl�.
There is one dataset of major ion concentrations for
post-monsoon fresh snow sample from Mt. Cho Oyu
reported by Balerna et al. (2003). Comparison shows
post-monsoon fresh snow also has higher ion concen-
trations than monsoon fresh snow, especially for Ca2+,
SO42� and NO3
�. This further confirms that low
concentrations of major ions in fresh snow occur during
monsoon season in the high elevation regions of the
central Himalayas, as noted by earlier researchers (Wake
et al., 1994; Marinoni et al., 2001; Kang et al., 2000;
Balerna et al., 2003). The low ion concentrations of
monsoon snow may reflect both decreased dust deposi-
tion (Wake et al., 1994; Shrestha et al., 1997) and
increased precipitation that washes out aerosols (Kang
et al., 2002c). The high ion concentrations in pre-
monsoon snow may result from dust deposition during
the peak in the dust-storm activity mainly in April and
May over Asia (Parrington et al., 1983; Gao et al., 1992;
Qian et al., 1997).
We also investigate the spatial distribution of fresh
snow chemical compositions in the vicinity of Mt.
Everest, in order to understand whether the crest of the
Himalayas is an effective barrier for transportation of
monsoon moisture from the south or dust storms from
the north, which is crucial to the interpretation of ice
core records recovered from the region. During mon-
soon season, Ca2+ concentrations in fresh snow are
higher in Mt. Cho Oyu (2) and the Hidden Valley (6),
both located in the northern slope of the Himalayas,
than those in other sites (Fig. 2), meanwhile, Ca2+
concentrations from two other northern sites: the ER
Glaciers (1) and the Dasuopu Glacier (3), are quite close
to the values in southern locations—the Khumbu Valley
(4, 5). For other species, the concentrations are more
homogeneous during monsoon season, and not as
dependent on geographical location as those on the
southern or northern slope of the Himalayas. Studies
also show that, during the pre-monsoon season, most of
major ions (e.g. Ca2+, SO42�, NO3
�) come from dust
deposition over the central Himalayas (Wake et al.,
1993; Kang et al., 2000). It seems that pre-monsoon
Ca2+, Na+ and Cl� concentrations are higher on the
northern slope of Mt. Everest and Xixabangma than
those on the southern slope of Mt. Everest (Fig. 3).
However, pre-monsoon SO42� concentrations are lower
on the northern slope of Mt. Everest than those on the
southern slope, while NO3� concentrations do not show
gradients between the northern and southern slopes.
Therefore, differences in fresh snow compositions
between the northern and southern slopes of the Mt.
Everest are not large compared with those between
monsoon and non-monsoon seasons. This may suggest
that the crest of the Himalayas is not a very effective
barrier to the spatial distribution of ion concentrations
in fresh snow for both pre-monsoon and monsoon
seasons, at least in the high mountain region of Mt.
Everest. More data will be needed to further understand
the role of the Himalayas in the distribution of snow
chemistry.
3.2. Chemical composition of snowpit samples
Table 2 summaries the mean ion concentrations for
snowpit samples collected from the ER Glacier on the
northern slope of Mt. Everest. Despite the different
sampling dates and snowpit depths, major ion concen-
trations from the three snowpits are consistent. An
obvious feature of snowpit chemistry is that Ca2+
concentrations are far higher than those of other species.
Comparison of ion concentrations between our 1998
fresh snow and three snowpits shows that, except for
Ca2+ concentrations, most of the species have similar
concentrations (Table 2). Our fresh snow samples have
very similar cation and anion concentrations, however,
a large excess of cations exists for snowpit samples due
to high Ca2+ concentrations (Table 2). This can be
comprehended considering that snowpits comprise
multi-season samples. Snowpit Na+/Cl� ratios suggest
that there is also an excess of Cl� compared to the sea-
salt Na+/Cl� ratio, in accord with results for fresh snow
samples.
Major ion concentrations versus depth for three
snowpits are presented in Figs. 3–5. Snowpit 1, elevation
of 6400m (Table 2), is located above the average
equilibrium line of the ER Glacier and the bottom of
the pit (close to an icy crust) is slightly dirty and
represents spring dust deposition. The variations of
Ca2+ concentration with depth show that Ca2+ spikes
ARTICLE IN PRESS
Fig. 3. Ion concentrations (meq l�1) versus depth in snowpit 1 collected in August 1998 at an elevation of 6400m in the East RongbukGlacier on the northern slope of Mt. Everest. Vertical dashed line represents the seasonal boundary.
S. Kang et al. / Atmospheric Environment 38 (2004) 2819–2829 2825
occurs in that layer (45–55 cm) (Fig. 3). From the top to
a depth of 45 cm in snowpit 1, ion concentrations are
relatively low, representing monsoon snow deposition.
Thus, we divide snowpit 1 into two seasons marked by a
dashed vertical line (Fig. 3). Most of the ions have
increasing concentrations in non-monsoon (or spring)
snow, except for NO3�.
Similar methods are applied to identify the monsoon
and non-monsoon snow layers for snowpits 2 and 3. For
snowpit 2, collected in May 2000, high ion concentra-
tions occur in the upper 30 cm snow representing non-
monsoon season deposition, following low ion concen-
trations at a depth of 30–85 cm related to monsoon
season snow, and high ion concentrations in the bottom
related to another non-monsoon season snow (Fig. 4).
The striking spikes of Ca2+ concentrations appear in
both non-monsoon snow layers with values as high as
88.5 and 55.4meq l�1. Detailed examination reveals thatNa+ and Cl� have more similar spikes (Fig. 4), so do
Ca2+ and Mg2+, reflecting close source region or
transport way for both species.
Snowpit 3 sampled in October 2002 has four
distinguishable monsoon and non-monsoon snow layers
(Fig. 5). High Ca2+ and Mg2+ concentrations are in
non-monsoon snow layers. Besides the spikes of Na+,
Cl� and K+ concentrations in non-monsoon seasons,
ARTICLE IN PRESS
Fig. 4. Ion concentrations (meq l�1) versus depth in snowpit 2 collected in May 2000 at an elevation of 6500m in the East RongbukGlacier on the northern slope of Mt. Everest. Vertical dashed lines represent the seasonal boundaries.
S. Kang et al. / Atmospheric Environment 38 (2004) 2819–28292826
high values of the three species also occur in monsoon
season of 2002 (at a depth of 50 and 90 cm) (Fig. 5).
Indeed, the monsoon peaks of three species can be
observed in both snowpit 1 (the depth of 35 cm) (Fig. 3)
and snowpit 2 (around 60 cm) (Fig. 4). High concentra-
tions of these species may be caused by local or regional
crustal aerosol input related to the summer circulation
as reported by Kang et al. (2002b). Sulfate and NO3�
also show spikes not only in non-monsoon snow layers
but also in monsoon layers.
Mean chemical composition of monsoon and non-
monsoon snow from three snowpits is calculated and
presented in Fig. 6. For snowpit samples collected in the
ER Glacier on the northern slope of Mt. Everest, there
is a striking seasonal difference for Ca2+ that is more
distinct than those for other species. Non-monsoon
snow Ca2+ is one order of magnitude higher than that
of monsoon Ca2+, consistent with the fresh snow
samples. Compared with the dramatic difference in
fresh snow SO42� between monsoon and pre-monsoon
seasons (one to two orders of magnitude) (Fig. 2), the
seasonal difference from snowpit samples is minor. The
ion elution process may cause the significant decrease of
SO42� concentrations in snow pack (Hou et al., 2002),
altering the original higher SO42� concentrations in non-
monsoon snow layers. Non-monsoon snow Na+, K+
and Cl� concentrations from snowpits are nearly two
times higher than monsoon values (Fig. 6), which agrees
with the fresh snow samples. The seasonal difference in
NO3� in snowpits is similar to that in fresh snow. Like
Ca2+, it seems that Mg2+ has more distinct seasonal
variations than other ions (Fig. 6): non-monsoon Mg2+
concentrations are about four fold higher that monsoon
values in snowpit samples.
ARTICLE IN PRESS
Fig. 5. Ion concentrations (meq l�1) versus depth in snowpit 3 collected in October 2002 at an elevation of 6500m in the East RongbukGlacier on the northern slope of Mt. Everest. Vertical dashed lines represent the seasonal boundaries.
Fig. 6. Comparison of mean ion concentrations (meq l�1) between monsoon and non-monsoon snow from three snowpit samplescollected in the East Rongbuk Glacier on the northern slope of Mt. Everest, central Himalayas.
S. Kang et al. / Atmospheric Environment 38 (2004) 2819–2829 2827
ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 38 (2004) 2819–28292828
Seasonal differences in snow chemical composition in
the vicinity of Mt. Everest offer a definitive indicator for
precisely dating ice cores and hence reconstructing past
change in climate and atmospheric chemistry. Snow
chemistry data from both fresh snow and snowpit
samples reveal that notable differences in Ca2+ con-
centrations exist between monsoon and non-monsoon
seasons, indicating that Ca2+ is perhaps the most
definitive ion for precise dating. Other species serve as
secondary references for dating ice cores.
4. Summary and conclusions
Snow chemical data from fresh snow and snowpit
samples collected in the ER Glacier on the northern
slope of Mt. Everest presented in this paper expand the
database of snow chemistry in the remote and high
mountain regions in the vicinity of Mt. Everest. Ion
balance calculations indicate that monsoon fresh snow
samples are in balance, however, snowpit samples have
an excess of cations due to high Ca2+ concentrations in
non-monsoon season. Fresh snow Na+/Cl� ratio shows
an excess of Cl� , relative to the sea-salt Na+/Cl� ratio,
in accord with the results from snowpit samples,
probably due to the scavenging of HCl in the air and/
or different sources between Na+ and Cl�.
Major ion concentrations from our 1998 fresh snow
samples collected during the monsoon season are similar
to other available data for monsoon fresh snow, but are
far lower than those for pre-monsoon season in the
vicinity of Mt. Everest. Comparison of chemical data
between monsoon and pre-monsoon fresh snow shows
striking seasonal differences in Ca2+ and SO42� con-
centrations: pre-monsoon Ca2+ is one order of magni-
tude higher than monsoon value; pre-monsoon SO42�
is one to two orders of magnitude higher than monsoon
value. Differences in NO3� concentrations between
pre-monsoon and monsoon seasons are also marked
but not as dramatic as those of Ca2+ and SO42�. Pre-
monsoon Na+ and Cl� concentrations are roughly
double higher than monsoon concentrations. Investiga-
tion of the spatial distribution of snow chemistry
indicates differences between fresh snow compositions
on the northern and southern slopes of Mt. Everest
region are neglectable compared with those from
monsoon to pre-monsoon seasons. This suggests that
the crest of the Himalayas is not a completely effective
barrier to the spatial distribution of fresh snow
chemistry during either non-monsoon or monsoon
seasons at least in the high mountain regions in the
vicinity of Mt. Everest.
The glaciochemistry from three snowpits collected in
the ER Glacier agrees with results from fresh snow in
the region. Calcium has the most striking seasonal
differences: non-monsoon snow Ca2+ is one order of
magnitude higher than that of monsoon snow consistent
with fresh snow samples. The dramatic seasonal
difference in fresh snow SO42� does not exist in snowpits
probably due to the ion elution process. Non-monsoon
snow Na+, K+ and Cl� concentrations from snowpits
are close to two times higher than monsoon values, in
agreement with fresh snow samples. Magnesium also has
a distinct seasonal variation, with a four-fold concentra-
tion difference in non-monsoon compared to monsoon
snow.
Snow chemistry data from both fresh snow and
snowpit samples reveal that striking differences in Ca2+
concentrations exist between monsoon and non-mon-
soon seasons, indicating that Ca2+ is perhaps the most
definitive ion for precise dating. Other species serve as
secondary references for dating ice cores. Therefore,
seasonal differences in snow chemical composition in the
vicinity of Mt. Everest offer a tool for precisely dating
ice cores and hence reconstructing past change in climate
and atmospheric chemistry.
Acknowledgements
This research is supported by the National Natural
Science Foundation of China (40121101, 40205007);
the Chinese Academy of Science (KZCX3-SW-339,
KZCX1-10-09, 02, KZCX2-SW-118); the US National
Science Foundation (ATM-0139481); the ‘‘Talent Pro-
ject’’ of CAS. We greatly appreciate helps from Dr. Hou
and Mr. Li in the field and suggestions from referees for
the improvement of our paper.
References
Balerna, A., Balerna, E., Pecci, M., Polesello, S., Smiraglia, C.,
Valsecchi, S., 2003. Chemical and radio-chemical composi-
tion of fresh snow samples from northern slope of
Himalayas (Cho Oyu range, Tibet). Atmospheric Environ-
ment 37 (12), 1573–1581.
Bryson, R.A., 1986. Airstream climatology of Asia. In: Proceed-
ings of the International Symposium on the Qinghai-Xizang
Plateau and Mountain Meteorology. American Meteorolo-
gical Society, Boston, MA, pp. 604–617.
Buck, C.F., Mayewski, P.A., Spencer, M.J., Whitlow, S.I.,
Twickler, M.S., Barrett, D., 1992. Determination of major
ions in snow and ice cores by ion chromatography. Journal
of Chromatography 594, 225–228.
Gao, Y., Arimoto, R., Zhou, M., Merrill, J., Duce, R.A., 1992.
Relationships between the dust concentration over eastern
Asian and the remote north Pacific. Journal of Geophysical
Research 97, 9867–9872.
Hou, S., Qin, D., Zhang, D., Ren, J., Kang, S., Mayewski, P.A.,
Wake, C.P., 2002. Comparison of two ice core chemical
records recovered from the Qomolangma (Mount Everest)
region. Annals of Glaciology 35, 266–272.
ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 38 (2004) 2819–2829 2829
Jenkins, M.D., Drever, J.I., Reider, R.G., Buchanan, T., 1987.
Chemical composition of fresh snow on Mount Everest.
Journal of Geophysical Research 92 (D9), 10999–11002.
Kang, S., Wake, C.P., Qin, D., Mayewski, P.A., Yao, Y., 2000.
Monsoon and dust signals recorded in the Dasuopu Glacier,
Tibetan Plateau. Journal of Glaciology 46 (153), 222–226.
Kang, S., Qin, D., Mayewski, P.A., Wake, C.P., Ren, J., 2001a.
Climatic and environmental records from the Far East
Rongbuk Ice Core, Mt. Everest. Episodes 24 (3), 176–181.
Kang, S., Qin, D., Mayewski, P.A., Wake, C.P., 2001b. Recent
180 years C2O42� records recovered from the ice core in
Mt. Everest: some environmental implications. Journal of
Glaciology 47 (156), 155–156.
Kang, S., Mayewski, P.A., Qin, D., Yan, Y., Zhang, D., Hou, S.,
Ren, J., 2002a. Twentieth century increase of atmospheric
ammonia recorded in Mt. Everest ice core. Journal of Geo-
physical Research 107(D21), 10.1029/2001JD001413, 4595.
Kang, S., Mayewski, P.A., Qin, D., Yan, Y., Hou, S., Zhang,
D., Ren, J., Kreutz, K., 2002b. Glaciochemical records
from a Mt. Everest ice core: relationship to atmospheric
circulation over Asia. Atmospheric Environment 36 (21),
3351–3361.
Kang, S., Qin, D., Mayewski, P.A., Sneed, S.B., Yao, T., 2002c.
Chemical composition of fresh snow on Xixabangma peak,
Central Himalaya, during the summer monsoon season.
Journal of Glaciology 48 (161), 337–339.
Mayewski, P.A., 1986. Snow chemistry from Xixabangma
Peak, Tibet. Journal of Glaciology 33, 542–543.
Meeker, L.D., Mayewski, P.A., Bloomfield, P., 1995. A new
approach to glaciochemical time series analysis. In: Delmas,
R.J. (Ed.), Ice Core Studies of Biogeochemical Cycles.
NATO ASI Series Vol. 130. Springer, Berlin, pp. 383–400.
Marinoni, A., Polesello, S., Smiraglia, C., Valsecchi, S., 2001.
Chemical composition of fresh snow samples from the
southern slope of Mt. Everst region (Khumbu-Himal region,
Nepal). Atmospheric Environment 35 (18), 3183–3190.
Parrington, J.R., Zoller, W.H., Aras, N.K., 1983. Asian dust:
seasonal transport to the Hawaiian islands. Science 220,
195–197.
Qian, Z., He, H., Zhao, Z., Chen, M., 1997. Grading standard
and case statistics of dust storm in northwest China. In:
Fang, Z., et al. (Ed.), Study on the Dust Storm in China.
China Meteorological Press, Beijing, pp. 1–10 (in Chinese).
Qin, D., Mayewski, P.A., Wake, C.P., Kang, S., Ren, J., Hou,
S., Yao, T., Yang, Q., Jing, Z., Mi, D., 2000. Evidence
for recent climate change from ice cores in the central
Himalayas. Annals of Glaciology 31, 153–158.
Qin, D., Hou, S., Zhang, D., Ren, J., Kang, S., Mayewski, P.A.,
Wake, C.P., 2002. Preliminary results from the chemical
records of an 80.4m ice core recovered from East Rongbuk
Glacier, Qomolangma (Mount Everest). Annals of Glaciol-
ogy 35, 278–284.
Shrestha, A.B., Wake, C.P., Dibb, J.E., 1997. Chemical
composition of aerosol and snow in the high Himalaya
during the summer monsoon season. Atmospheric Environ-
ment 31 (17), 2815–2826.
Shrestha, A.B., Wake, C.P., Dibb, J.E., Whitlow, S.I., 2002.
Aerosol and precipitation chemistry at a remote Himalayan
site in Nepal. Aerosol Science and Technology 36 (4),
441–456.
Thompson, L.G., Yao, T., Mosley-Thompson, E., Davis, M.E.,
Henderson, K.A., Lin, P.N., 2000. A high-resolution
millennial record of the south Asian monsoon from
Himalayan ice cores. Science 289, 1916–1919.
Valsecchi, S., Smiraglia, C., Tartari, G., Polesello, S., 1999.
Chemical composition of Monsoon deposition in the
Everest region. The Science of the Total Environment 226,
187–199.
Wake, C.P., Mayewski, P.A., 1993. The spatial variation of
Asian dust and marine aerosol contributions to glaciochem-
ical signals in central Asia. In: Young, G. (Ed.), Interna-
tional Symposium on Snow and Glacier Hydrology.
Kathmandu, IAHS Publication No. 218, pp. 385–402.
Wake, C.P., Mayewski, P.A., Xie, Z., Wang, P., Li, Z., 1993.
Regional variation of monsoon and desert dust signals
record in Asian glaciers. Geophysical Research Letters 20,
1411–1414.
Wake, C.P., Dibb, J.E., Mayewski, P.A., Xie, Z., Li, Z., Wang,
P., Qin, D., 1994. The chemical composition of aerosols
over eastern Himalaya and Tibetan Plateau during low dust
periods. Atmospheric Environment 28, 695–704.
Yao, T., Duan, K., Xu, B., Wang, N., Pu, J., Kang, S., Qin, X.,
Thompson, L., 2002. Temperature and methane changes
over the past 1000 years recorded in Dasuopu Glacier
(central Himalaya) ice core. Annals of Glaciology 35,
379–383.
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