02368nas a2200229 4500008004100000245007900041210006900120260001200189520162900201653002401830653001301854653002101867653002001888653001401908653002501922100002401947700002501971700002201996700002302018700002402041856007302065 2020 eng d00aNutrient uptake in the supraglacial stream network of an Antarctic glacier0 aNutrient uptake in the supraglacial stream network of an Antarct c08/20203 a

In polar regions, where many glaciers are cold‐based (frozen to their beds), biological communities on the glacier surface can modulate and transform nutrients, controlling downstream delivery. However, it remains unclear whether supraglacial streams are nutrient sinks or sources and the rates of nutrient processing. In order to test this, we conducted tracer‐injections in three supraglacial streams (62 to 123 m long) on Canada Glacier in the Taylor Valley, of the McMurdo Dry Valleys, Antarctica. We conducted a series of additions including: nitrate (N), N + phosphate (P), N+ P + glucose (C), and N+C. In two reaches, N‐only additions resulted in N uptake. The third reach showed net N release during the N‐only addition, but high N uptake in the N+P addition, indicating P‐limitation or N+P co‐limitation. Co‐injecting C did not increase N‐uptake. Additionally, in these systems at low N concentrations the streams can be a net source of nitrogen. We confirmed these findings using laboratory‐based nutrient incubation experiments on sediment collected from stream channels on Canada Glacier and two other glaciers in the Taylor Valley. Together, these results suggest there is active biological processing of nutrients occurring in these supraglacial streams despite low sediment cover, high flow velocities and cold temperatures, modifying the input signals to proglacial streams. As glaciers world‐wide undergo rapid change, these findings further our understanding of how melt generated on glacier surfaces set the initial nutrient signature for subglacial and downstream environments.

10aMcMurdo Dry Valleys10anitrogen10anutrient tracers10anutrient uptake10asediments10asupraglacial streams1 aBergstrom, Anna, J.1 aGooseff, Michael, N.1 aSingley, Joel, G.1 aCohen, Matthew, J.1 aWelch, Kathleen, A. uhttps://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JG00567904038nas a2200205 4500008004100000245015700041210006900198260001200267300001600279490000800295520333900303100001903642700002103661700002403682700001503706700002403721700001703745700002403762856004603786 2018 eng d00aNear-surface refractory black carbon observations in the atmosphere and snow in the McMurdo Dry Valleys, Antarctica and potential impacts of foehn winds0 aNearsurface refractory black carbon observations in the atmosphe c01/2018 a2877 - 28870 v1233 a

Measurements of light absorbing particles in the boundary layer of the high southern latitudes are scarce, particularly in the McMurdo Dry Valleys (MDV), Antarctica. During the 2013 - 2014 austral summer near-surface boundary layer refractory black carbon (rBC) aerosols were measured in air by a single particle soot photometer (SP2) at multiple locations in the MDV. Near-continuous rBC atmospheric measurements were collected at Lake Hoare Camp (LH) over two months and for several hours at more remote locations away from established field camps. We investigated periods dominated by both up and down-valley winds to explore the causes of differences in rBC concentrations and size distributions. Snow samples were also collected in a 1m pit on a glacier near the camp. The range of concentrations rBC in snow were 0.3 1.2 ± 0.3 μg-rBC/L-H2O, and total organic carbon were 0.3 1.4 ± 0.3 mg/L. The rBC concentrations measured in this snow pit are not sufficient to reduce surface albedo, however, there is potential for accumulation of rBC on snow and ice surfaces at low elevation throughout the MDV which were not measured as part of this study. At LH, the average background rBC mass aerosol concentrations was 1.3 ng/m3. rBC aerosol mass concentrations were slightly lower, 0.09 1.3 ng/m3, at the most remote sites in the MDV. Concentration spikes as high as 200 ng/m3 were observed at LH, associated with local activities. During a foehn wind event, the average rBC mass concentration increased to 30-50 ng m-3. Here we show the rBC increase could be due to resuspension of locally produced BC from generators, rocket toilets, and helicopters, which may remain on the soil surface until redistributed during high wind events. Quantification of local production and long-range atmospheric transport of rBC to the MDV is necessary for understanding the impacts of this species on regional climate. 

 

1 aKhan, Alia, L.1 aMcMeeking, Gavin1 aSchwarz, Joshua, P.1 aXian, Peng1 aWelch, Kathleen, A.1 aLyons, Berry1 aMcKnight, Diane, M. uhttp://doi.wiley.com/10.1002/2017JD027696