@article {2841,
	title = {Fossil Fuel Combustion Emission From South Asia Influences Precipitation Dissolved Organic Carbon Reaching the Remote Tibetan Plateau: Isotopic and Molecular Evidence},
	journal = {Journal of Geophysical Research: Atmospheres},
	volume = {123},
	year = {2018},
	month = {Apr-06-2019},
	pages = {6248 - 6258},
	abstract = {The dissolved organic carbon in precipitation (water-soluble organic carbon, WSOC) can provide a carbon subsidy to receiving ecosystems. The concentrations, isotopic signatures (δ13C/Δ14C), and molecular signatures (transform ion cyclotron mass spectrometry) of WSOC being delivered to Nam Co{\textemdash}a remote site on the inland Tibetan Plateau (TP){\textemdash}were compared to those of WSOC in the snowpack, and in wet deposition from urban cities fringing the TP. The average WSOC concentration at Nam Co (1.0 {\textpm} 0.9 mg C L-1) was lower than for the large cities (1.6 to 2.3 mg C L-1) but higher than in the snowpack samples (0.26 {\textpm} 0.09 mg C L-1). Based upon radiocarbon data, it is estimated that 15 {\textpm} 6\% of Nam Co WSOC was fossil derived, increasing to 20 {\textpm} 8\% for snowpack WSOC, 29 {\textpm} 4\% for Lhasa WSOC, and 34 {\textpm} 8\% for the three cities. Transform ion cyclotron mass spectrometry results revealed that the abundance of dissolved black carbon and sulfur-containing molecules of WSOC increased in the order Nam Co < snow pack < urban. The enrichment in 14C and depletion in dissolved black carbon and sulfurous organic molecules of Nam Co WSOC was suggestive of low, but still detectable inputs of fossil-derived organics to WSOC on the remote TP. Backward air mass trajectories for the precipitation events at Nam Co suggested that the fossil fuel contributions to WSOC in Nam Co region originated mainly from South Asia. This study provides novel radiocarbon age, chemistry, and source evidence that anthropogenic WSOC is delivered to the remote TP, one of the most remote regions on Earth.},
	doi = {10.1029/2017JD028181},
	url = {http://doi.wiley.com/10.1029/2017JD028181},
	author = {Li, Chaoliu and Chen, Pengfei and Kang, Shichang and Yan, Fangping and Tripathee, Lekhendra and Wu, Guangjian and Qu, Bin and Sillanp{\"a}{\"a}, Mika and Yang, Di and Dittmar, Thorsten and Stubbins, Aron and Raymond, Peter A.}
}
@article {2840,
	title = {Aged dissolved organic carbon exported from rivers of the Tibetan Plateau},
	journal = {PLOS ONE},
	volume = {12},
	year = {2017},
	month = {Feb-05-2019},
	pages = {e0178166},
	abstract = {The role played by river networks in regional and global carbon cycle is receiving increasing attention. Despite the potential of radiocarbon measurements (14C) to elucidate sources and cycling of different riverine carbon pools, there remain large regions such as the climate-sensitive Tibetan Plateau for which no data are available. Here we provide new 14C data on dissolved organic carbon (DOC) from three large Asian rivers (the Yellow, Yangtze and Yarlung Tsangpo Rivers) running on the Tibetan Plateau and present the carbon transportation pattern in rivers of the plateau versus other river system in the world. Despite higher discharge rates during the high flow season, the DOC yield of Tibetan Plateau rivers (0.41 gC m-2 yr-1) was lower than most other rivers due to lower concentrations. Radiocarbon ages of the DOC were older/more depleted (511{\textpm}294 years before present, yr BP) in the Tibetan rivers than those in Arctic and tropical rivers. A positive correlation between radiocarbon age and permafrost watershed coverage was observed, indicating that 14C-deplted/old carbon is exported from permafrost regions of the Tibetan Plateau during periods of high flow. This is in sharp contrast to permafrost regions of the Arctic which export 14C-enriched carbon during high discharge periods.},
	keywords = {Carbon cycle, Carbon dioxide, Climate change, Rain, Rivers, Surface water, Tibetan people, TIBETAN PLATEAU},
	doi = {10.1371/journal.pone.0178166},
	url = {https://dx.plos.org/10.1371/journal.pone.0178166},
	author = {Qu, Bin and Sillanp{\"a}{\"a}, Mika and Li, Chaoliu and Kang, Shichang and Stubbins, Aron and Yan, Fangping and Aho, Kelly Sue and Zhou, Feng and Raymond, Peter A.},
	editor = {Lin, Senjie}
}
@article {2461,
	title = {Spatial Variation in the Origin of Dissolved Organic Carbon in Snow on the Juneau Icefield, Southeast Alaska},
	journal = {Environmental Science \& Technology},
	volume = {49},
	year = {2015},
	month = {Jun-10-2015},
	pages = {11492 - 11499},
	abstract = {Dissolved organic carbon (DOC) plays a fundamental role in the biogeochemistry of glacier ecosystems. However, the specific sources of glacier DOC remain unresolved. To assess the origin and nature of glacier DOC, we collected snow from 10 locations along a transect across the Juneau Icefield, Alaska extending from the coast toward the interior. The Δ14C-DOC of snow varied from -743 to -420{\textperthousand} showing progressive depletion across the Icefield as δ18O of water became more depleted (R2 = 0.56). Older DOC corresponded to lower DOC concentrations in snow (R2 = 0.31) and a decrease in percent humic-like fluorescence (R2 = 0.36), indicating an overall decrease in modern DOC across the Icefield. Carbon isotopic signatures (13C and 14C) combined with a three-source mixing model showed that DOC deposited in snow across the Icefield reflects fossil fuel combustion products (43{\textendash}73\%) and to a lesser extent marine (21{\textendash}41\%) and terrestrial sources (1{\textendash}26\%). Our finding that combustion aerosols are a large source of DOC to the glacier ecosystem during the early spring (April{\textendash}May) together with the pronounced rates of glacier melting in the region suggests that the delivery of relic DOC to the ocean may be increasing and consequently impacting the biogeochemistry of glacial and proglacial ecosystems in unanticipated ways.},
	issn = {0013-936X},
	doi = {10.1021/acs.est.5b02685},
	url = {http://pubs.acs.org/doi/10.1021/acs.est.5b02685http://pubs.acs.org/doi/pdf/10.1021/acs.est.5b02685},
	author = {Fellman, Jason B. and Hood, Eran and Raymond, Peter A. and Stubbins, Aron and Spencer, Robert G.M.}
}
@article {2460,
	title = {Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources},
	journal = {Environmental Research Letters},
	volume = {9},
	year = {2014},
	month = {Jan-05-2014},
	pages = {055005},
	abstract = {Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon
(DOC). Characterizing DOC in Mendenhall Glacier out flow (southeast Alaska) we document a
seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as
a ubiquitous feature of glacier out flow. We observed no systematic depletion in Δ14C-DOC with
increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ13C-DOC,Δ14C-DOC and fluorescence signatures appear to have been in fluenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ 14 C-DOC of stream samples at the out flow (-181.7 to-355.3{\textperthousand}) was comparable to the Δ 14 C-DOC for snow samples from the accumulation zone (-207.2 to-390.9{\textperthousand}), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century.},
	keywords = {alaska, dissolved organic carbon, glacier, organic matter, radiocarbon},
	doi = {10.1088/1748-9326/9/5/055005},
	url = {http://iopscience.iop.org/article/10.1088/1748-9326/9/5/055005/meta},
	author = {Spencer, Robert G M and Vermilyea, Andrew and Fellman, Jason and Raymond, Peter and Stubbins, Aron and Scott, Durelle and Hood, Eran}
}
@article {2459,
	title = {Source and biolability of ancient dissolved organic matter in glacier and lake ecosystems on the Tibetan Plateau},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {142},
	year = {2014},
	month = {Jan-10-2014},
	pages = {64 - 74},
	abstract = {The Tibetan Plateau is the world{\textquoteright}s largest and highest plateau and holds the largest mass of ice on Earth outside the ice-sheets of Greenland and Antarctica, as well as abundant lakes. This study examined the molecular and isotopic signatures of dissolved organic matter (DOM) along with its biolability in glacier ice, glacier-fed streams, and alpine lakes on the Tibetan Plateau. The aim was to assess the sources of DOM and the potential of DOM to provide a carbon subsidy to downstream ecosystems. Tibetan glaciers and glacier streams exhibited low dissolved organic carbon (DOC) concentrations (17.7{\textendash}27.9 μM) and ancient DOC radiocarbon ages (749{\textendash}2350 ybp). The optical properties, stable carbon isotope ratios (δ13C-DOC) and the molecular composition (Fourier transform ion cyclotron resonance mass spectrometry) of Tibetan glacier DOM are consistent with data from other glacier systems around the world. The geochemical signatures and the ancient apparent ages of Tibetan glacier DOM suggest a significant fraction is derived from the atmospheric deposition of pre-aged, possibly fossil fuel derived organics. Within the Tibetan alpine lakes, DOC was also ancient (525{\textendash}675 ybp), due to either inputs of pre-aged organics from glacier runoff, direct deposition, or due to the aging of organics in situ (i.e. a radiocarbon reservoir effect). The glacier ice and glacier stream sites exhibited high biolability of DOC and so provide a carbon subsidy to downstream environments that will change as glaciers on the Tibetan Plateau recede.},
	issn = {00167037},
	doi = {10.1016/j.gca.2014.08.006},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0016703714005018http://api.elsevier.com/content/article/PII:S0016703714005018?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0016703714005018?httpAccept=text/plain},
	author = {Spencer, Robert G.M. and Guo, Weidong and Raymond, Peter A. and Dittmar, Thorsten and Hood, Eran and Fellman, Jason and Stubbins, Aron}
}
@article {2458,
	title = {Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers},
	journal = {Nature Geoscience},
	volume = {5},
	year = {2012},
	month = {Jul-02-2013},
	pages = {198 - 201},
	abstract = {Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems1. This finding runs counter to logical perceptions of age{\textendash}reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest2. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter1, 3, 4. Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows.},
	keywords = {Atmospheric chemistry, Biogeochemistry, Cryospheric science},
	issn = {1752-0894},
	doi = {10.1038/ngeo1403},
	url = {http://www.nature.com/doifinder/10.1038/ngeo1403},
	author = {Stubbins, Aron and Hood, Eran and Raymond, Peter A. and Aiken, George R. and Sleighter, Rachel L. and Hernes, Peter J. and Butman, David and Hatcher, Patrick G. and Striegl, Robert G. and Schuster, Paul and Abdulla, Hussain A. N. and Vermilyea, Andrew W. and Scott, Durelle T. and Spencer, Robert G. M.}
}
