@article {271,
	title = {Contrasting lipid biomarker composition of terrestrial organic matter exported from across the Eurasian Arctic by the five great Russian Arctic rivers},
	journal = {Global Biogeochemical Cycles},
	volume = {22},
	year = {2008},
	note = {id: 819; 261FT Times Cited:10 Cited References Count:112Y},
	abstract = {Surface sediments outside the great Russian Arctic rivers (GRARs; Ob, Yenisey, Lena, Indigirka, and Kolyma) were investigated for their lipid biomarker composition to elucidate compositional distinctions of the exported organic matter (OM) across this continent-scale climosequence of the Siberian Arctic. The lipid biomarker composition is dominantly terrestrial (high molecular weight (HMW) n-alkanols, n-alkanoic acids, n-alkanes; branched glycerol dialkyl glycerol tetraethers (GDGTs), beta-sitosterol, other sterols, and triterpenoids) with only minor marine contributions (e. g., the ratio of terrigenous-to-aquatic n-alkanes was 17-80, the TOC/TN ratio was 10-16, and the branched and isoprenoid tetraether (BIT) index > 0.88). There is a large contribution of C-23 and C-25 homologues relative to other long-chained n-alkanes, suggesting substantial contribution of probably Sphagnum-derived OM. The C-23 and C-25 contribution decreases eastward, signaling either a decrease in the potential contribution of Sphagnum or a shift within the n-alkane distribution of Sphagnum species or increased aeolian input, due to more arid conditions in the east. Other distinctions in molecular OM composition across the climosequence include increased concentrations of both HMW n-alkanoic acids and beta-sitosterol relative to HMW n-alkanes in the eastern sediments. This suggests that the OM exported by the eastern GRARs is, despite their higher bulk radiocarbon ages, less degraded, which is consistent with increasing permafrost and a shorter annual thaw period in eastern Siberia. Taken together, this benchmark study of the current composition of terrestrially exported OM suggests distinguishing continent-scale trends in molecular composition of the OM across the west-east set of GRARs, which reflects both differences in vegetation and climate. If the climate in the eastern Russian Arctic region becomes more like the current state in the western part, these results would predict a greater degree of decomposition of the old terrestrial OM released by the eastern GRARs and thus greater remineralization and release as CO2 and methane.},
	issn = {0886-6236},
	doi = {10.1029/2007gb002974},
	author = {van Dongen, B. E. and Semiletov, I. and Weijers, J. W. H. and Gustafsson, O. R.}
}
@article {270,
	title = {Pan-Arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and PAH source apportionment markers in estuarine surface sediments},
	journal = {Global Biogeochemical Cycles},
	volume = {22},
	year = {2008},
	note = {id: 820; 307ZP Times Cited:3 Cited References Count:89Y},
	abstract = {A pan-arctic geospatial picture of black carbon (BC) characteristics was obtained from the seven largest arctic rivers by combining with molecular combustion markers (polycyclic aromatic hydrocarbons) and radiocarbon (C-14) analysis. The results suggested that the contribution from modern biomass burning to BC ranged from low in the Yukon (8\%) and Lena (5\%) Rivers to high in the Yenisey River (88\%). The Mackenzie River contributed almost half of the total arctic fluvial BC export of 202 kton a(-1) (kton = 10(9) g), with the five Russian-Arctic rivers contributing 10-36 kton a(-1) each. The C-14-based source estimate of fluvially exported BC to the Arctic Ocean, weighted by the riverine BC fluxes, amount to about 20\% from vegetation/biofuel burning and 80\% from C-14-extinct sources such as fossil fuel combustion and relict BC in uplifted source rocks. Combining these pan-arctic data with available estimates of BC export from other rivers gave a revised estimate of global riverine BC export flux of 26 x 10(3) kton a(-1). This is twice higher than a single previous estimate and confirms that river export of BC is a more important pathway of BC to the oceans than direct atmospheric deposition.},
	issn = {0886-6236},
	doi = {10.1029/2007gb002994},
	author = {Elmquist, M. and Semiletov, I. and Guo, L. D. and Gustafsson, O.}
}
@article {2049,
	title = {Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export},
	journal = {Global Biogeochemical Cycles},
	volume = {18},
	year = {2004},
	note = {806knTimes Cited:99
Cited References Count:51
},
	month = {Mar 10},
	abstract = {Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were characterized for elemental composition (total organic carbon, TOC, black carbon, BC, and total N, as well as major and trace elements), isotopic signature (delta(13)C, delta(15)N, Delta(14)C, epsilon(Nd), Sr-87/Sr-86), and organic molecular composition to better understand river export variations over the large spatial scale of the Siberian Arctic. On average, 79 +/- 9\% of the total C in sediments was organic while 21 +/- 9\% was inorganic. BC made up 9 +/- 4\% of the TOC pool, with a general increasing trend from west to east along the Siberian coast. The combined Nd- and Sr-isotopes (epsilon(Nd) and Sr-87/Sr-86) were used to define two distinct sediment sources between east and west Siberian regions with the Khatanga River as a boundary. Data from pyrolysis-GC/MS of the sedimentary organic carbon (SOC) indicated an increase in the freshness of the organic matter from west to east on the Siberian Arctic coast, with increasing relative abundance of furfurals (polysaccharides) with respect to nitriles. Values for the delta(13)C of SOC ranged from -27.1\% (mostly terrigenous) to -23.8\%, while delta(15)N increased from east to west (3.1 to 5.2\%) with a significant correlation with C/N ratio. Values for the Delta(14)C of SOC ranged from -805 to -279\%, with a consistent trend increasing from the east (Indigirka River) to the west (Ob River). These D 14 C values corresponded to a 14 C age of 2570 +/- 30 yBP in the Ob estuary and 13,050 +/- 50 yBP in the Indigirka estuary. Most importantly, D 14 C values were significantly correlated with the ratio of BC/TOC (R-2 = 0.91, n = 6), consistent with the distribution pattern of increasing permafrost zone from the west to the east along the Siberian coast. Together, our results suggest that older OC was derived from the release of recalcitrant BC during permafrost thawing and riverbank and coastal erosion, likely enhanced by ongoing environmental changes in the northern ecosystem.},
	keywords = {arctic ocean, BLACK CARBON, climate, CO2, continental-shelf, flux, isotopic composition, lena river, MATTER, ocean, organic carbon, quantification, Sediment},
	isbn = {0886-6236},
	doi = {10.1029/2003GB002087},
	url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&amp;SrcAuth=Alerting\&amp;SrcApp=Alerting\&amp;DestApp=WOS\&amp;DestLinkType=FullRecord;UT=WOS:000220432900001},
	author = {Guo, L. D. and Semiletov, I. and Gustafsson, O. and Ingri, J. and Andersson, P. and Dudarev, O. and White, D.}
}
