Potential genesis and implications of calcium nitrate in Antarctic snow

Among the large variety of particulates in the atmosphere, calcic mineral dust particles have highly reactive surfaces that undergo heterogeneous reactions with atmospheric acids contiguously. The association between nssCa²⁺, an important proxy indicator of mineral dust, and NO₃⁻, a dominant anion in the Antarctic snowpack, was analysed. A total of 41 snow cores ( ∼  1 m each) that represent snow deposited during 2008–2009 were studied along coastal–inland transects from two different regions in East Antarctica – the Princess Elizabeth Land (PEL) and central Dronning Maud Land (cDML). Correlation statistics showed a strong association (at 99 % significance level) between NO₃⁻ and nssCa²⁺ at the near-coastal sections of both PEL (<i>r</i>  =  0.74) and cDML (<i>r</i>  =  0.82) transects. Similarly, a strong association between these ions was also observed in snow deposits at the inland sections of PEL (<i>r</i>  =  0.73) and cDML (<i>r</i>  =  0.84). Such systematic associations between nssCa²⁺ and NO₃⁻ are attributed to the interaction between calcic mineral dust and nitric acid in the atmosphere, leading to the formation of calcium nitrate (Ca(NO₃)₂) aerosol. Principal component analysis revealed common transport and depositional processes for nssCa²⁺ and NO₃⁻ both in PEL and cDML. Forward- and back-trajectory analyses using HYSPLIT model v. 4 revealed that southern South America (SSA) was an important dust-emitting source to the study region, aided by the westerlies. Particle size distribution showed that over 90 % of the dust was in the range  &lt;  4 µm, indicating that these dust particles reached the Antarctic region via long-range transport from the SSA region. We propose that the association between nssCa²⁺ and NO₃⁻ occurs during the long-range transport due to the formation of Ca(NO₃)₂ rather than to local neutralisation processes. However, the influence of local dust sources from the nunataks in cDML and the contribution of high sea salt in coastal PEL evidently mask such association in the mountainous and coastal regions respectively. Ionic balance calculations showed that 70–75 % of NO₃⁻ in the coastal sections was associated with nssCa²⁺ (to form Ca(NO₃)₂). However, in the inland sections, 50–55 % of NO₃⁻ was present as HNO₃. The study indicates that the input of dust-bound NO₃⁻ contributes a significant fraction of the total NO₃⁻ deposited in coastal Antarctic snow

Major ion chemistry of snow cores along a transect in central Dronning Maud Land, Antarctica

Among the large variety of particulates in the atmosphere, calcic mineral dust particles have highly reactive surfaces that undergo heterogeneous reactions with nitrogen oxides contiguously. The association between Ca2+, an important proxy indicator of mineral dust and NO3-, a dominant anion in the Antarctic snow pack was analysed. A total of 41 snow cores (~ 1 m each) that represent snow deposited during 2008-2009 were studied along coastal-inland transects from two different regions - the Princess Elizabeth Land (PEL) and central Dronning Maud Land (cDML) in East Antarctica. Correlation statistics showed a strong association (at 99 % significance level) between NO3- and Ca2+ at the near-coastal sections of both PEL (r = 0.72) and cDML (r = 0.76) transects. Similarly, a strong association between these ions was also observed in snow deposits at the inland sections of PEL (r = 0.8) and cDML (r = 0.85). Such systematic associations between Ca2+ and NO3- is attributed to the interaction between calcic mineral dust and nitrogen oxides in the atmosphere, leading to the possible formation of calcium nitrate (Ca(NO3)2). Forward and back trajectory analyses using HYSPLIT model v. 4 revealed that Southern South America (SSA) was an important dust emitting source to the study region, aided by the westerlies. Particle size distribution showed that over 90 % of the dust was in the range < 4 µm, indicating that these dust particles reached the Antarctic region via long range transport from the SSA region. We propose that the association between Ca2+ and NO3- occurs during the long range transport due to the formation of Ca(NO3)2. The Ca(NO3)2 thus formed in the atmosphere undergo deposition over Antarctica under the influence of anticyclonic polar easterlies. However, influence of local dust sources from the nunataks in cDML evidently mask such association in the mountainous region. The study indicates that the input of dust-bound NO3– may contribute a significant fraction of the total NO3- deposited in Antarctic snow

Major ion chemistry and selected snow accumulation rates of snow cores along two transects in central Dronning Maud Land and Princess Elizabeth Land

This dataset includes basic information (location and depth) and major ion chemistry (Sodium, Chloride, Calcium, Nitrate) of snow cores from East Antarctic ice sheet. The snow cores were collected from two different regions - central Dronning Maud Land (cDML) and Princess Elizabeth Land (PEL) during the austral summer of 2008-09

Relation between surface topography and sea-salt snow chemistry from Princess Elizabeth Land, East Antarctica

Previous studies on Antarctic snow have established an unambiguous correlation between variability of sea-salt records and site specific features like elevation and proximity to the sea. On the other hand, variations of Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt;/Na&lt;sup&gt;+&lt;/sup&gt; ratios in snow have been attributed to the reaction mechanisms involving atmospheric acids. In the present study, the annual records of Na&lt;sup&gt;+&lt;/sup&gt;, Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt; and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; were investigated using snow cores along a 180 km coast to inland transect in Princess Elizabeth Land, East Antarctica. Exceptionally high Na&lt;sup&gt;+&lt;/sup&gt; concentrations and large variations in Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt;/Na&lt;sup&gt;+&lt;/sup&gt; ratios were observed up to 50 km (&amp;sim;1100 m elevation) of the transect. The steepest slope in the entire transect (49.3 m km&lt;sup&gt;&amp;minus;1&lt;/sup&gt;) was between 20 and 30 km and the sea-salt records in snow from this area revealed extensive modifications, with Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt;/Na&lt;sup&gt;+&lt;/sup&gt; ratios as low as 0.2. Statistical analysis showed a strong association between the slope and variations in Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt;/Na&lt;sup&gt;+&lt;/sup&gt; ratios along the transect (&lt;i&gt;r&lt;/i&gt; = −0.676, 99% confidence level). While distance from the coast accounted for some variability, the altitude by itself has no significant control over the sea-salt ion variability. However, the steep slopes influence the deposition of sea-salt aerosols in snow. The wind redistribution of snow due to the steep slopes on the coastal escarpment increases the concentration of Na&lt;sup&gt;+&lt;/sup&gt;, resulting in a low Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt;/Na&lt;sup&gt;+&lt;/sup&gt; ratios. We propose that the slope variations in the coastal regions of Antarctica could significantly influence the sea-salt chemistry of snow

Organic Carbon in Antarctic Snow: Spatial Trends and Possible Sources

Organic carbon records in Antarctic snow are sparse despite the fact that it is of great significance to global carbon dynamics, snow photochemistry, and air–snow exchange processes. Here, surface snow total organic carbon (TOC) along with sea-salt Na⁺, dust, and microbial load of two geographically distinct traverses in East Antarctica are presented, viz. Princess Elizabeth Land (PEL, coast to 180 km inland, Indian Ocean sector) and Dronning Maud Land (DML, ∼110–300 km inland, Atlantic Ocean sector). TOC ranged from 88 ± 4 to 928 ± 21 μg L^–1 in PEL and 13 ± 1 to 345 ± 6 μg L^–1 in DML. TOC exhibited considerable spatial variation with significantly higher values in the coastal samples (<i>p</i> < 0.001), but regional variation was insignificant within the two transects beyond 100 km (<i>p</i> > 0.1). Both distance from the sea and elevation influenced TOC concentrations. TOC also showed a strong positive correlation with sea-salt Na⁺ (<i>p</i> < 0.001). In addition to marine contribution, in situ microorganisms accounted for 365 and 320 ng carbon L^–1 in PEL and DML, respectively. Correlation with dust suggests that crustal contribution of organic carbon was marginal. Though TOC was predominantly influenced by marine sources associated with sea-spray aerosols, local microbial contributions were significant in distant locations having minimal sea-spray input

The Himalayan cryosphere: A critical assessment and evaluation of glacial melt fraction in the Bhagirathi basin

The cryosphere constitutes an important subset of the hydrosphere. The Himalayan cryosphere is a significant contributor to the hydrological budget of a large river system such as the Ganges. Basic data on the cryosphere in the Himalaya is inadequate and also has large uncertainties. The data on glacial melt component in the Himalayan rivers of India also shows high variability. The Gangotri glacier which constitutes nearly a fifth of the glacierized area of the Bhagirathi basin represents one of the fastest receding, large valley glaciers in the region which has been surveyed and monitored for over sixty years. The availability of measurement over a long period and relatively small glacier-fed basin for the Bhagirathi river provides suitable constraints for the measurement of the glacial melt fraction in a Himalayan river. Pre- and post-monsoon samples reveal a decreasing trend of depletion of δ18O in the river water from glacier snout (Gaumukh) to the confluence of the Bhagirathi river with the Alaknanda river near Devprayag. Calculations of existing glacial melt fraction (∼30% at Rishikesh) are not consistent with the reported glacial thinning rates. It is contended that the choice of unsuitable end-members in the three component mixing model causes the overestimation of glacial melt component in the river discharge. Careful selection of end members provides results (∼11% at Devprayag) that are consistent with the expected thinning rates