Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 ) carbon: 2 erences in ff Discussions supersaturation in Biogeosciences 3 , S. P. Pugach 2 2 . The annual Lena River 1 − . During all seasons the river is 4 for the East Siberian Arctic Shelf 4 , O. V. Dudarev in the Lena delta channels may reach 4 1,2 , and O. Gustafsson 2 concentration decreases. Significant inter- , TOC, and their sum (TC) has been found. 2 2 2094 2093 and dissolved CH 2 to the Arctic Ocean. , D. Kosmach , N. E. Shakhova 1 4 2 ects on total organic (TOC) and inorganic (TCO ff compared to the atmosphere: up to 1.5–2 fold in summer, and 2 concentration decreases to 5–20 nM towards the sea, which sug- 4 , I. I. Pipko , C. P. McRoy 1,2 2 budget in coastal waters. Instead, the seabed appears to be the source 4 This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. International Arctic Research Center, University of Alaska Fairbanks, Fairbanks AKLaboratory 99775, of Arctic Studies, Pacific Oceanological Institute, Far-Eastern Branch ofStockholm Russian University, Dept. of Applied Environmental Science (ITM) and the Bert Bolin that provides most of the CH input of eroded terrestrial carbonwhich onto is the about shelf 4 Tg. ofof The the primary Lena Laptev greenhouse and River gases: is Eastsupersaturated CO characterized Siberian in by seas, CO relatively high4–5 concentrations fold in winter.the This adjacent coastal results sea. in Spots a100 of nM, narrow dissolved but CH zone the of CH significantgests CO only a minor(ESAS) role CH of riverborne export of CH discharge of particulate organichigh carbon estimate). (POC) If may we be insteaditation accept equal of Lisytsin’s to (1994) 85–95% 0.38 statement Tg of concerningthen (moderate total the only to precip- particulate about matter 0.03–0.04The Tg (PM) Lena’s (and of POC POC) POC export on reaches would the the then marginal be Laptev “filter”, two Sea orders from of the magnitude Lena less River. than the annual charge causes opposite e TOC concentration increases, while TCO annual variability in meanThis values variability of is TCO determined bythe changes Lena in River discharge, land because hydrologySeptember a which negative and cause correlation mean di may discharge be in foundfor August between water (a TC to time in travel shift from ofthe Yakutsk about to Lena one the discharge month Laptev is Sea). is required Total estimated carbon to entering the be sea almost with 10 Tg C y The Lena River integrates biogeochemicalsignal signals reaches from far its out vastbon drainage over basin into the and mineral Arctic its carbon, Ocean.watershed, and can be Transformation mineral considered of a carbon riverine quasi-equilibrated into processes. organic Increasing the car- the organic Lena dis- form in the Lena River Abstract Biogeosciences Discuss., 8, 2093–2143, 2011 www.biogeosciences-discuss.net/8/2093/2011/ doi:10.5194/bgd-8-2093-2011 © Author(s) 2011. CC Attribution 3.0 License. A. N. Charkin 1 USA 2 Academy of Sciences, Vladivostok3 690041, Russia Centre for Climate Research, Stockholm, Sweden Received: 12 February 2011 – Accepted:Correspondence 16 to: February 2011 I. – P. Semiletov Published: ([email protected]) 3 MarchPublished by 2011 Copernicus Publications on behalf of the European Geosciences Union. On the biogeochemical signature ofLena the River from its headwatersArctic to Ocean the I. P. Semiletov 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | from northern 4 from land, dominated ff and CH 2 in the north (Conway et al., 1994; 4 ect biogeochemical cycling and carbon ff and CH 2 2096 2095 from river streams can significantly change the 4 and CH 2 , and accelerated coastal erosion could dramatically alter car- ff erent seasons and years to not be mislead by such variability in the ff ) exchange that ignore water-borne fluxes might significantly overesti- 4 (and CH 2 Among the Siberian Rivers the Lena is considered to be the major source of total Documented significant increases in the annual amplitude of Siberian river dis- to the sea is still under some debate. source of carbon andrestrial nutrients carbon to in the thethe ESAS shelf terrestrial water organic seas. column matter (e.g., has Recentet Semiletov documented al., large-scale et significant al., 2010; studies degradation 2007; Vonk of Anderson of from et et ter- the al., al., shelf 2010a; 2009; of Sanchez-Garcia Alling Fram the et Strait Laptev al., (Anderson Sea, 2011). et rich al.,Amerasian Further, 1998), in shelf surface possibly dissolved and water determining Arctic OM, bacterial Basin follows (WheelerRiver production Gakkel is et over Ridge also al., the considered 1996; towards to Opsahl be etal., the al., 1995; main 1999). Rachold sediment The et source Lena al., for the 2004) Laptev although Sea the (Alabyan amount et of suspended sediment delivered spanning over di interpretation of a single year expedition. OM to the Arcticby Ocean organic-rich (Gordeev et soils, al., ice-complexes, 1996). and the Summer runo mires of northern Asia, is an important ecosystems and changestially in resulting the in atmospheric greaterthe circulation fluvial export and export of land terrestrial ofbalance carbon hydrology, terrestrial in will poten- organic the certainly matter East a Siberian (OM).Romankevich Arctic and Changes shelf Vetrov, in seas 2001; (Alling Sanchez-GarciaStein et et al., and al., 2010; Macdonald, Charkin 2011;processes et 2004; Semiletov and al., et van constructing 2011; al., budgets Dongen to 2005; cessing et calculate of regional al., river the input 2008). biogenic and and shelf Comprehending sea anthropogenic pro- materials controlling requires comprehensive studies charges and air temperatureset in al., their 2000; Semiletov watershedsof et over the al., the seasonal 2000) past cycle have ofIPCC, 30 coincided atmospheric 2001), years with CO indicating an (Savelieva a increasefeedback general in increase loop the in could amplitude climatic operate variability. Therefore, between a the positive emission of CO change are largely unknown,environmental change understanding on them a time is scale critical of human to concern. our understanding of regional or even global carbonet cycle al., (Kling 2011). et al., TheseCO 1991; authors Richey cautioned et that al., directmate 2002; measurements terrestrial Bastviken of carbon accumulation. land-atmosphere in A hypothesized terrestrial climate-change-driven organic increase carbonincreased inputs river to runo thebon Arctic budgets Ocean and biogeochemical throughterrestrial organic cycles. permafrost carbon thawing, across While the Arctic the land/ocean fate margin and and consequent transport gas ex- processes of rivers form an importantto link serving between as the naturaltheir large-scale land extensive integrators and drainage of ocean basins, carbon-related(GSARs) the carbon of processes coastal pools. carbon occurring and export nutrients in of In playArctic a the addition Ocean critical Great evasion role of in Siberian the CO Arctic biogeochemical regime rivers of the Freeman et al., 2001;Ocean Guo is et expected al., toSemiletov 2007). increase et al., with Siberian 2000; increasing freshwaterexport Peterson temperatures discharge et of (Savelieva to al., old et terrigenous the 2002), al., organic whichvial Arctic carbon in 2000; exported that turn to has may recently result the2010a; been in Gustafsson ocean documented greater et to (Guo river al., be ethydrometeorological flu- 2011). al., regime, Rivers including 2004; integrate soil van variabilitythermokarst condition, in Dongen development, the permafrost et all components seasonal al.,water of the thaw, 2008; supply the variables and for Vonk that the et determine rivers al., and atmospheric chemical and weathering ground in their watershed. Thus, arctic The Arctic Ocean is surroundeding by rate permafrost, under which conditions is of being warming(ACIA, degraded which 2004; at are Richte-Mengers an most et increas- pronounced al., indischarge Siberia (Lyon 2006). and and Destouni, Permafrost Alaska 2010), thawing and accelerates carbon both losses river from soils (Finlay et al., 2006; 1 Introduction 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4 ), 2 ects on ff ) nitrite (N-NO Kapitan Danilkin Mekhanik Kulibin 3 , MV Neptun from Yakutsk to the Lena River ), nitrate (N-NO 4 erent years are presented in Fig. 1a, b, c. (late August–September 2008) and during ff 2098 2097 , obtained along the Lena River and in the adjacent 4 Captain Ponomarev erent seasons before and after freeze-up over the period ff (September 2005), small boat Mekhanik Kulibin ). This route was repeated onboard the MV 2 in September 1997 (Fig. 1c). Some data obtained in the Laptev Auga 500 ml) for gas chromatography (GC) measurements of dissolved CH (TCO and dissolved CH ∼ from the Lena River to the Laptev Sea, and further to the Arctic Ocean. 2 2 ff Dunay was sampled by Niskin bottles and measured onboard the hydrographic , and atmospheric processes over the Arctic. The emphasis of this work is to ff CO ff p This study is based on an extensive observational data set collected from seven field Hydrometeorological analyses explaining the significant role of the Lena River- oratories at the University of Alaska, Fairbanks. 2.2 Salinity, nutrients and dissolved organicChlorinity carbon (titrated, Cl), salinity (S),and phosphate (P-PO total dissolved N andgraphic P techniques in prescribed water by samplesdissolved Ivanenkov organic were and carbon determined (DOC) Bordovsky by were (1978). determinedby traditional using the oceano- Total samples (TOC) Shimadzu sealed and TOC-5000 in high-temperature glass catalytic tubes oxidation technique in the lab- vessel (HV) Sea onboard MV (September 2006), MV winter expedition (April–May 2002) areJune to also early discussed August 2003) (Fig. waterNiskin 1c). sampling bottles from During from the flooding surface the to (late upper the stream bottom down was made the by Lena River to the Laptev Sea (Fig. 1b). From late August to early Septemberonboard 1995 (Fig. the 1a), motor surface water vesseldelta samples (MV) were and taken Tiksiduring Bay slow in cruising. the Thesealed water Laptev bottles samples ( Sea, were transferred by immediatelyand plastic to total hermetically bucket CO fromin the late bow August ofRiver to the runo early ship September 1998 (Fig. 1a). Shelf water influenced by Lena 2.1 Field expeditions Data were collected in1995–2008. di The study areas visited in di 2 Data sets and methods river runo summarize information about important biogeochemicalthat fluxes, with link a runo focus on carbon, Data on part of the Laptevgeneral understanding Sea, of are how the considered. Arctic atmosphere-land-shelf This system works. information is critical for developing a 2006 and 2008 aredissolved also and discussed particulate organic (Fig. carbonapproach 1). and to carbonate understanding We system the present components inter-annualand results as its and of a chemical seasonal first signature measurements variability in of ofconnections the the adjacent between waters Lena the of River the hydrochemical Laptev regime Sea. of We briefly the discuss Laptev Sea, as influenced by between western and eastern Siberiaogy, sea in ice atmospheric conditions, circulation tectonic patterns,shelf structure, land (Semiletov and hydrol- et biological al., communities 2000, on 2005). the Siberian seasons in the Lenathe river Lena system, river plume extending inlate from the July the recipient to headwaters Laptev early Sea. nearfrom August Ust’-Kut Studies Ust-Kutsk of to include to the 2003, one Lena expedition the Delta. from time Other of data obtained high in water 1995, levels 1997, along 1998, 2002, the 2005, Lena River, Laptev Sea system inpaikher the (1980), arctic Zakharov freshwater (1996) budget andas can Semiletov the be et seminal al. found Siberian (2000). incant river Nikiforov We role because and view in changes the ice Sh- in Lena and Lenathe freshwater River freshwater River sources budget hydrology of to the play the Laptev a Transpolar Sea. Current signifi- The through Lena its River e also forms a natural boundary 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ), ers K ff + L 1–2%. V ± / G V ( G system study. C 2 = L after the Poropac C cients from Stumm 4 erence in TA did not ff ffi ) was calculated using L C to CH ( 2 4 ) was determined by a GC e (1982): G ff were based on three standard so- 2 ). 2100 2099 was also determined by FID. Water for gas analysis was computed from pH and TA, and from pH and 4 gas solubility as a function of temperature and salin- 2 2 erence is ignored here because the error in calculating 2 ff ) is influenced mainly by the uncertainty in the measured CO 2 leakage into the atmosphere, was used to measure pH in units between values of pH measured in open and closed CO p 2 2 p CO − p ( in the equilibrated gas phase (C . This di 1 2 4 − 4 we used a gas chromatograph, TSVET-530 or LKHM-80MD, with a with concentrations of 0.73, 1.02, and 1.99 mM that were prepared 2 3 values in freshwater, we applied apparent constants for dissociation 2 01 pH). The CO . erence not exceeding 1%. Detail description for all measurements and 2 0 ff and CH CO C (Semiletov, 1993). The measurements are reproducible to within ± di 2 ◦ p 2 erent techniques were used for pH measurements. pH measurements were ff erence of a few 10 according to the methods advocated by UNESCO (1987). We used the equation C with hydrogen carrier gas; a stripping GC technique similar to that described ◦ CO ff 2 p head-space technique. The concentrationthe of main dissolved static CH head space equation of Vitenberg and Io lutions of Na gravimetrically in fresh, distilledcolumn water. was done Conversion in a ofNi) Ni-catalyst CO at column 400 (14 cm Chromaton,The 80–100 concentration mesh, of coated dissolved CH by was collected in hermetically sealedface in glass the bottles manner from recommended justConcentration by below Dickson of the and sea CH Goyet or (1994) for river CO sur- 2.6 TCO To measure TCO Poropac T (1.5 m, 80–120 mesh)at and a 30 flame-ionization detector (FID) runin isothermally Weiss (1981) was used. The calibrations of TCO and seawater as determinedcalculate by Lyman and Meerbachof et carbonic al. acid in advocatedPlummer UNESCO by and (1987). Millero Busenburg To (1979, (1982),and Morgan and 1981), (1981). individual thermodynamic Agreement ion among constantsthe results activity from of all coe applied techniquescalculations was can good be with found elsewhere (Pipko et al., 2002, 2011; Semiletov et al., 2007). pH value ( TCO of Weiss (1974) to representity, CO and the equations ofdence Millero of the (1995) apparent for dissociation temperature constants and for salinity boric and (chlorinity) carbonic depen- acids in freshwater partial pressure of CO Edmond’s methods (Dickson and Goyet, 1994)exceed showed 0.02 that mmol kg the di pH cells to be negligible. 2.5 Total alkalinity and Samples for measurements of totalGoyet alkalinity (TA) (1994) were obtained and following analyzed Dicksonin and within an 12 open to cell(Ivanenkov 24 using and h 25 Bordovsky, of ml 1978). of collection Comparison water by of with TA direct determination 0.02 indicator by N Bruevich’s titration and HCl according to Bruevich’s method cal cell, which avoided CO samples taken from sites inwere all used seasons to check after the 1997.in Nernst NBS the slope commercial of Arctic standard the river electrode bu pH and pairs. di shelf Because water natural variability samples is large (up to 1 pH unit), we consider the were measured attio the mass University spectrometer of (IRMS)http://www.uaf.edu/water/ASIF/ASIF.html Alaska (Schell Fairbanks et using al., 1998; a Guo Finnigan et2.4 isotope al., ra- 2004; pH see website at Two di made in situ: an openmeasurements electrochemical prior cell to was used and for including surface 1997 samples (Semiletov, and 1999a). for A winter closed electrochemi- During flooding (late June to earlydynamics August and 2003) the the suspended composition particulatenents and matter (POC (PM) isotopic and signatures PON) of werethe its measured Laptev organic from the Sea material upper compo- (Fig. stream 1b). down the Lena Concentration River to and isotopic signatures of POC and PON 2.3 Particulate organic carbon (POC) and nitrogen (PON) 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4 and cient. 2 ffi ) drainage 2 ) contains no 0.25 km gas standards 2 km ∼ 4 6 were treated with km 10 2 6 × 10 5 . × 2 4 . cial terminology, the delta ∼ ffi and TCO shore permafrost. The upper 4 C onshore (see discussion in ff ◦ making it the second largest in is a gas partitioning coe 2 12 erent seasons (Fig. 1a, b). K ff km 3 ∼ − 10 × 5 . . According to o 2 2102 2101 E, which is located in one of the most remote using a precision multivalve positioned at ambient ◦ C, while it is 4 10 km ◦ > 1 − g) of organic carbon (assuming low mean OC concen- 15 including the Laptev and East Siberian, and Russian part 2 10 shore layer of relict permafrost varies between 50 and 200 m. = km ff 6 N and 105–141 ◦ 10 are volumes in the gas (G) and liquid (L) phases of the closed head- × 1 G . V 2 ∼ and L V The Lena basin is generally located in the continuous permafrost zone where the The delta of the Lena River occupies 28 tration equal 0.5%permafrost w/w) degradation, that including could coastal be erosion available (Semiletov, 1999a, for b). biogeochemical cycling Taking into through but some geophysical and borehole’s datafragile show component that the of subsea the permafrost modern is100 cryosphere m the because most sediment mean layer temperature is forShakhova the et rougly upper al., 2010a, b;amount Nicolsky of and buried Shakhova, OM 2010; with Rachold anical et average cycling al., 3–5% due 2007). C to by A thawing weight vast 100 and is m erosion presently of of reentering onshore permafrost biolog- and inless o Siberia than (tundra 9400 Gt and (1 northern Gt taiga, 9 frozen layer depth variestends from down to 50 600 m m, though tothrough large 1500 permafrost lakes m. and (Grigoriev rivers and can Kunitsky, In 2000). beSea underlain the It the by is delta taliks depth assumed extending area that of underNote the the the that o Laptev permafrost estimation of ex- the subsea permafrost distribution is mostly based on modeling, data and the Tiksibranch (Bb) Hydromet of data the forwinter mouth low 1953–1990s receives water (Sidorov, and about summer 1992), 24%receives high about and the water, 70% respectively, 28% Bykovskaya and while of 54%, the andabout the Trofimovskaya branch the 3% total Tumatskaya and and discharge Olenekskaya 8–10%, branches during the receive respectively. Bb hydrological According regime to reflects Antonov allRiver important (1964) delta. features and of Because Ivanov other thelected branches (1970), Bb of our the main has Lena set been of the samples most in accessible this and channel in investigated, di we col- the world (after theAbout Mississippi 30 River) 000 and lakes the areonly largest located 100 delta in lakes in the with delta, thebegins surface 90% Eurasian downstream area of with continent. Stolb a Island typical (Fig. 1a). size Following of Antonov (1964) for 1936–1950s McClelland, 2011). landscapes: boreal andtundra, northern and semi-desert taiga, tundra. forestthe The tundra, ESAS Lena shrub ( watershed tundra, areaof exceeds open-woodland the the entire Chukchi area Sea),Ocean. of which The in ESAS alone turn constituteswith is almost a the 20% mean broadest of depth the of andfrom total only shallowest the area 50 shelf Lena’s m. of vast in the The drainageongoing Arctic changing the area Ocean, changes fresh World in water in the and the ESAS biogeochemical can East signal be Siberia considered (Savelieva as et an al., indicator 2000; of Semiletov et al., 2000; 3 General description of the LenaThe River Lena Basin River originatesbasin near within Lake 53–71 Baikalareas from of the a Eurasian continent large andLena ( contains River a basin large variety is of phytogeographically geological an features. area The of transition among various Siberian were done in September 2005, 2006,with and FID. For 2008 calibration using in a 2005,in Micro-Tech-8160 GC 2006, a equipped and balance 2008 of weShakhova used air et certified al. (Air CH (2005, Liquide, 2007a, USA). b,ples 2010a, stored This b) more technique and than 4 has Shakhova h andmercuric been before Semiletov measuring chloride successfully (2007). dissolved to used Sam- CH poison by biological activity. space system with thermostatCalibration set was done to with ambient, clean CH and temperature. The total precisionbetween of 3–5%; variation this was technique, usually whichtov, due was 1993; to used instability Semiletov in until et shipboard 2003, electricity al., varied (Semile- 1996a). High-precision measurements of dissolved CH where 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 1 − ers 8‰, ff . 0 ± 0 erent per- . ff 27 − ) from Gordeev C were found in 1 − 13 δ 360–500 Gt) trapped ∼ C values of the organic 25‰ with a mean value cm deep. Therefore the 13 − 4 δ in the Bykovskaya channel 1 ) to the water column. − 2 to 10 3 30‰ and − and CO 4 erent for rivers situated in di , about half the mean value (38.5 mg l ff 1 − plants. Similar values of in the channel outlets (Fig. 2). Note, that two C values was reported by Rachold and Hub- 2104 2103 1 with an additional 2/3 ( 3 − 13 4 δ erent between rivers in any permafrost environment ff 540–750 Gt of CH ∼ ) in the lower river to as much as 30 mg l erence may be related to the use of filters with non-standard, most 1 ff C in river POC ranged between − 90% of ESAS was land that was flooded by the sea during transgres- 13 erent summer months when the major water and solid discharges occur. ∼ δ ff cm north of the Arctic Circle, but in southern mountainous areas discontinu- 2 27‰. A similar range of POC seas: river-derived PM and POC − C values for particulate OM throughout the river, with an average of Values of Our observations of PM distribution along the Lena River from the upper stream The water balance of the Siberian Rivers situated in the permafrost region di 13 the Yenisey estuary (Kodina et al., 1999) and Lena estuary (McClelland et al., 2008). GF/F borosilicate filters. near berten (1999) for the Lena, Khatanga,fraction and of Yana basins. the The surfacepart bottom of sediment, the measured Laptev inThese Sea the results during delta agree and September withδ the 1997, Rachold southeastern show and a Hubberten terrestrialreflecting (1999) the origin who dominant for contribution found the of nearly OM. C constant tent we measured in thereported river by was 19.4 Romankevich mg and l et Vetrov (2001) al. and (1996). theService. Both mean used (34 mg The the l di datalikely obtained smaller, by pores the in Soviet Union the Hydrometeorological latter studies compared to the now canonical Whatman time as observed in June–Julylow 2003 (10–15 (Fig. mg 2a, l b, c).of PM the concentration delta, increased but from decreased a stations to 5–10 (encircled mg area l in Fig.August 2) in were the accomplished beginning in ofdoubling the of the Bykovsky the “second channel PM flooding in concentrations early wave”.earlier. compared Both with The August the observed stations surveycoastal exhibit PM accomplished a erosion, increase one which week in is the common delta in channels this may area also (Grigoriev, be 1993). related The to mean the PM con- erosion in di (Ust’-Kut) in late June toSeptember of August 1995 of and 2003, 1998, mid-stream andmost down all (Yakutsk) to riverine in PM the late settles Laptev August in Sea the to (Fig. delta, 1) early even demonstrate during that spring/summer al- high river discharge transgression. Therefore it is important to study the role of the Lena River and coastal charge. Alternatively, Bauch et al.tion (2001) of OM believe that in the the Laptev increased Sea Holocene is deposi- mainly the result of coastal erosion due to the sea level 4 Results and discussion 4.1 Fluvial transport and sedimentation in theBoucsein Lena et al. River (2000) argue deltain that and at composition the adjacent of beginning of sedimentmaterial) the Holocene OM on a (increase the significant change of Laptev fresh-water Sea alginite continental and slope was immature due plant to increased Lena River dis- ous permafrost (permafrost islands)regime may of be groundwater from flow 10 mafrost is environments, significantly and also di di and rivers in non-permafrost environmentsSemiletov (van et Dongen al., et 2000). al., 2008; Guo et al., 2004; Additionally, bottom erosion and subsea2001; talik Shakhova and formation Semiletov, 2007; (Romanovskii Dudarev andof et Hubberten, al., old 2008) carbon can (predominantly be in a the significant form source of CH from that of riversmafrost in table) other beneath regions the because seasonallyinfluences the thawed land layer upper hydrology is surface and a of hydrochemistry. water-impermeable10 The the sheet to permafrost permafrost that 10 table (per- depth varies from sion, we may assume that1800 the Gt upper of 100 m organic shelfestimated sediment carbon. to layer itself hold contains This atbelow as least reservoir free also gas (Shakhova consiststo et al., relocate of 2010a). terrestrial ESAS Thus, organic the hydrate Lena carbon River deposits between serves as the a land pathway and shelf carbon megapools. account that 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 93%). = g) deliv- 12 10 = 27‰, typical of higher − of ter C value up to 1500–2000 µatm in , ) 13 2 δ and an annual river discharge of mar 1 CO C − p 13 δ 70%) become 86% and 52% of terrestrial − = ter C values of observed, marine, and terrestrial , which was obtained in 2003 along the Lena 2106 2105 C 1 13 − 13 δ δ ( / 5‰. Thus the river OM discharge has probably no C signature to the Laptev Sea which was dispersed . in the bottom sediment can be used to quantitatively 13 100 26 δ − × org ) C < 21‰, typical of phytoplankton (Walsh et al., 1989; Naidu et 13 (terrestrial C) can be calculated from the data as mar − ter δ C C ter of 13 13 C C variability in POC are discussed briefly by Rachold and Hub- δ δ 13 mar − 13 27.70‰) is constant in Neelov Bay of the delta and close to val- δ δ 27.54‰) measured in the sediments of the Laptev Sea between Big C − Co − 13 13 δ δ ( = we calculated the “mean” solid discharge to be 10.5 Tg (1 Tg C value ( 3 27.16 to 13 − δ The PM data obtained in the Dmitry Laptev Strait where the river PM signal is negligi- Calculations made for the entire ESAS indicate that there is a significant amount of The spatial trends of A second Lena River “flooding wave” in summer of 2008 brought unusually high Using the mean PM concentration of 20 mg l summer, and 5000 µatm incesses winter especially and in plays the a south-eastern significant area role of in the biogeochemical Laptev pro- Sea, and western area of end-member isotopic mixing model forsect POC (Vonk applied et along al., the 2010a) Kolyma whicherosion paleo-river revealed was tran- that substantial the (51–60%). proportion of OC derived from coastal ble show that “new production”terrestrial is formed signal from of the olddirect terrigenous influence carbon on with marine a productivity, typical whiletion coastal of erosion and “fresh” consequent old degrada- terrestrial organics builds up terrestrial OC stored within sediments,influenced especially by in coastal the erosion: near between shore thethe Dmitry zone OC Laptev most Strait strongly and is theIn Kolyma almost mouth, contrast, all the ofern sediments terrestrial underneath area) origin transformed are (from Pacificn-alkanes almost measurements 81% – half in to origin the of surface water 100%, marine sediment (the OC mean origin (Vetrov East- et CTOM (Fig. al., 2008) 3). and a That three result is agreed well with CTOM(%) where “o”, “mar”, and “ter”sediment. refer to If the we take theplants, and two a end members toal., 2000), be then a the CTOM valuesand for the the East Eastern Siberian area Sea: (boundedOC, Western respectively geochemical by area (Fig. CTOM 3). estimate the contribution ofFollowing terrestrial Walsh organic at matter al. (1989), (CTOM)trial the to end-member amount the of ESAS organic sediment. carbon (OC) derived from terres- significantly from year-to-year depending onand hydrometeorological ocean. conditions over land compared with western Siberia (Guoet et al., al., 2008). 2004; Gustafsson et al., 2011; van Dongen amount of PM/POC withfurther light north of thetion Lena from Delta the (Sanchez-Garcia coastalthe et erosion eroded al., material was 2011). from small,the At the because partitioning that foreshore low time, between zone winds/waves contribu- to fluvial did the and not sea “coastal removed (Charkin erosion” et POC al., input 2011). to the Thus, sea can vary Siberian Sea Rivers, the Indigirka(Ivanov and and Kolyma, Piskun, is also 1999). limitedIndigirka, Note, by that Kolyma) the the and near-mouth OM areas local exportedless coastal degraded by erosion, than the their despite western eastern high Siberian GSARssistent counterparts bulk (Lena, with (Ob radiocarbon increasing and ages, Yenisey), permafrost which is and are con- a shorter annual thaw period in eastern Siberia tov, 1999b). 525 km ered through the delta channels.we use Annual a discharge mean of POC POCRiver value during may of flooding be (moderate 0.75 equal mg or l to highment estimates). 0.38 concerning Tg the If if precipitation we of accept 85–95% Lisytsin’ster”, of (1994) then total state- only PM about (and 1 POC) Tg onthe of the PM, Lena marginal and “fil- 0.03–0.04 River. Tg of Similarly, POC reaches in the summer Laptev Sea and from fall the solid discharge of other major East Reasons for the berten (1999), though clarificationthe of this issue will requireues additional ( study. Note, that Lyakhovsky Island and Cape Svyatoy Nos where coastal erosion dominates (Semile- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in the surface layer and 1 − 4 Tg) was made by Rachold ∼ 2108 2107 40 m in depth) is several times higher than it was ) at the coastal bottom depressions of the Laptev 2 > ) which is outside the area of direct river sediment − 1 − 100 mg l 0.26), while ratios typical of the Lena River are 10 times higher > = in the near bottom layer, Semiletov et al., 2005) obtained over the west- 1 − ESAS All the geochemical data obtained in the summertime expeditions (1999–2007, ex- The Quartz/Feldspar (Q/FS) ratios in the western and eastern East Siberian Sea Several studies show that transport of coastally eroded material into the Laptev During August–September, when the river discharge is low but the rates of coastal et al., 2005; Vetrov et al., 2008; Karlsson et al., 2011). Thus, we argue that in the et al., 2011), becausecondition of preventing the removal abrupt of secondal., eroded summertime 2011). carbon flooding from wave foreshore and to low the wind sea (Charkincept et of 2008 whensee Sanchez-Garcia anomalously et high al., thetional 2011; environment Lena Charkin in River et the solidby al., Lena coastal discharge 2011) River erosion was rather prodelta clearly than obtained: and showable by CN the that riverine stable input. Buor-Khaya the isotope Gulf This deposi- data, conclusion is C/N agrees dominated well ratios, with and avail- the distribution of biomarkers (Semiletov Indigirka and Kolyma,1999). is also Then we limited canplays by argue major the that role in transport near-mouthonly accumulation of areas in of the summer/fall (Ivanov carbon eroded of and in 2008 materialto we this Piskun, (Semiletov, the obtained part 1999ab) adjacent a part of significant of the contribution the of Arctic Laptev Lena Sea Ocean. and POC western burden Note east that Siberian Sea (Sanchez-Garcia that the PM andzone CTOM/POC where plume most from of the thedirect Lena Lena River influence is burden of limited settles. the by The Lena the pattern transport also narrow of shows nearshore PM a into negligible are the the East Siberian same Sea. (Q/FS (between 2 andan 2.3) insignificant (Serova direct and influenceSea. Gorbunova, of 1997). Note Lena that River This in transport summer-fall evidence of the also PM solid into indicates discharge the of East the Siberian major East Siberian Rivers, ESAS and its contribution to sedimentationexport was of not studied terrOM yet. in To the illustratefor anomalous ESAS the we period show 2003–2007 the (Fig. integratedsupport 4) plume the obtained of east hypothesis PM of of and the athe CTOM Lena dominating ESAS in Delta. role sedimentation POC of and These dynamics coastal observations of erosion the (Semiletov, carbon/carbonate 1999a, system. b) It in can be seen Alling et al., 2010). However, the fate of the Lena CTOM in POC plume across the The East Siberian Sea is2011; strongly Pipko impacted et by al., the 2008, Lena 2011; River Semiletov plume et (Anderson al., 2000; et Shakhova al., and Semiletov, 2007; per limit of thisSiberian range seas is which close gives totov, a our 2001) higher previous which estimate “mean” is made annual aPOC for value POC discharge the about flux into Laptev two value the and orders of sea.et of East al. 2.5 Higher Tg magnitude (2004). annual higher (Semile- estimation than ( the Lena River 4.2 Processes controlling the distribution and loss of fluvial POC across the old organic carbon. and East Siberian seas ranges2000)” between with 40–70 Tg a (Are, meanterrestrial 1999; organic Grigoriev carbon carbon and onto concentration Kunitsky, the of 3%. shelf may Annual therefore transport range of from eroded 1.2 Tg to 2.1 Tg. The up- 25.4 mg l ern part of thereported ESAS for inner shelf the ( varov Lena et river al., – 1999).Dmitry Laptev Laptev shelf Note, Strait system that ( input the during (Dudarev et highest the al., PM 2003). “surgeorganisms The concentrations freshet” finding (up were of to (Pivo- anomalously observed 100–200 high gSea in concentrations (Gukov C of the et benthic m al., 1999) could be associated with near-shore accumulation of eroded Semiletov, 1999a, b; Semiletov et al.,al., 2004, 2007; 2010). Anderson Detail et al., discussion 2009,Sea for 2011; can dynamics Alling be et of found the below carbonate (Sect. system 4.2). in the Lena-Laptev erosion are highest, the mean PM concentration (24.2 mg l the East-Siberian Sea where coastal retreat is highest (Pipko et al., 2005, 2008, 2011; 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | TOC) in the , TOC, 4 + 2 2 Sphagnum TCO = throughout the major 2 and TOC concentrations increase 2 C years) terrOM in these coastal wa- 14 . 2 2110 2109 , and TC values is consistent with the maximum 2 contribution but the youngest terrOM occurs toward the Sphagnum varies inversely to TOC concentration down the Lena River (Figs. 5, 6). In the 2 erences in vegetation and climate (Guo et al., 2004; Gustafsson et al., 2011; van shore transport of eroded material, in accumulation of carbon in this part of the Arctic TCO Our studies to date show that terrOM entering sub-Arctic Baltic and Eurasian Arctic ff ff coastal waters of Tiksi Baydrastically. This (sites increase 40 in and TOC, TCO 41) TCO 5-day voyage, in late August to earlyAt September that 1995, 41 time, sites the wereened surveyed surface (Fig. by waters 1a). the of river the discharge.pH) Laptev and The Sea silicate major near (an components the indicator ofBecause delta of the the were continental river carbon strongly includes crust cycle fresh- water weathering) (TCO all entering were of from sampled a Yakutia, (Table the basin 1). signature thatbe from extends identified. throughout the almost major tributaries, the Aldan and Viljuy rivers, can posed by this system. Summer To understand the carbon cycle intion the along Lena a River we 1700 km carried section out a from shipboard Yakutsk to investiga- Tiksi on the Laptev Sea coast. During a layer, though in 1996–1998 andWe 2006 vertical consider sampling the sections summer wereof also the surface conducted. whole chemical because datacolored measurements dissolved from of organic the temperature, carbon river (CDOM), conductivity,water dissolved TOC, column to pH, oxygen, (except be and of TCO representative deeps)transported were by the the same. Lena Riverflood The is periods. total a carbon The significant (TC contribution fatethe to of adjacent the this sea sea, carbon or especially pool, accumulated during whether in the consumed coastal more zone, or is less one rapidly of in the important questions 4.3.1 The carbonate system in theIn river summer and 1995, near-shore we zone beganLena a River study delta of and adjacent the shelf carbonate waters system (Fig. and 1). dissolved In CH general we sampled the surface 4.3 Dynamics of the carbonate system in the Lena River – Laptev Sea system al., 2011). Taken together, allterrestrially recent exported benchmark POM suggest studies distinguishing ofcomposition continent the of –scale current the trends composition in OM of molecular di across the west-east EurasianDongen shelf et seas, al., 2008; which Vonk reflectsmore et both al., like 2010a, the b). current Ifgreater state the degree climate (comparing in in with the the western westOM ESAS Siberia) released region Siberian of by becomes decomposition region, the of coastal these thegreater erosion old results remineralization and terrestrial and would the release Lena predict and as a others CO eastern GSARs and thus (65% during the 5-day boxnearly transit). 20 times This more translated rapid into thanfor a for the terrDOC, degradation which total rate makes for both terrOM pools terrPOC indexes degradation. equally between important the Similar Kalix-Baltic trends and foring GSARs may POC-biomarkers systems be and similar suggest on degradation that the the Eurasian early Arctic shelf process- (Vonk et al., 2008, 2010b; Gustafsson et is a key contributorters; to the the pre-aged greatest (1000swest of (Vonk and Gustafsson,dation 2009; during Vonk settling et and al.,et in 2010a). the al., surface 2010a). There sediment was A (Sanchez-Garciative also simple et river rapid al., box input, degra- model 2011; settling Vonk was(Gustafsson fluxes, et parameterized al., and with 2000; advective measurements van export,ual Dongen of et biomarkers, and advec- al., bulk was 2008). POC and solved The bulk model for DOC. was degradation Rapid run terrPOC for both degradation individ- was constrained o Ocean; this conclusion alsoet supports al. the (2010a). conclusion of Bauch et al. (2001)seas and follows continent-scale Vonk trends in molecular and isotopic composition. 1995–2005 period, the Lena River solid discharge played a minor role, compared with 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 2 C 3 ◦ − 60). . 0.91) 0 − ranges values, − 2 was 7.83 and TOC and TOC 0.47 mM, = 25 2 2 r = 25 C in 1998 vs. ◦ C from 18.6 ◦ values measured near 25 changed in an opposite manner 03 mM (except for site 40 which 2 . C change in 1995. The larger tem- 0 ◦ 0.2 mM as TOC) contributed by the ect. Increasing the Lena discharge ± ff ∼ , 48 . 2 2112 2111 ) and mesozooplankton biomass (890 mg m in the river from Yakutsk to Stolb Island (where ), TOC, and their sum (TC), Table 2. We sug- 1 2 2 − d 0.0 as TCO 3 and TOC shows high variability: (1) TCO 0.1 mM as TOC) due to inflow of the Viljuy River in − ∼ ∼ 2 , 2 0.85 mM) from Yakutsk to Stolb Island, to 0.84–1.38 mM = obtained in 1995. We found a high negative correlation ( concentration decreases (Pipko et al., 2010). This phenomenon ) in August 1995, was about 89% of the discharge in August 2 erence in the hydrological regime is also reflected in the tempera- 1 2 ), while the mean TC value in 1998 was 87% of the TC value ff − C in Tiksi Bay, compared to a 7 ects on dissolved organic and inorganic carbon: TOC concentra- 1 ◦ s ff − 3 s values and river discharge. In the river system the TC distribution 3 2 0.2 mM as TCO ∼ 1.06 mM) in the delta0.59 mM) and from Tiksi Bay; Yakutsk (2) to TOC Stolb decreases Island, from 0.39–0.93 to mM 0.38–0.53 mM (mean = = C in 1995. An increase in river discharge is in agreement with an increase in the ◦ The fate of organic-rich Lena River water in the Laptev Sea, when plotted against The interannual di Cauwet and Sidorov (1996) also found a positive correlation between TOC values Comparison of our results obtained along the Lena River and in the nearshore zone Highest TOC concentrations (Table 1) were found in the Lena mid-stream between (0.58 mM vs. 0.60 mM, respectively) near zero salinity (Fig. 7). These values reflect 10.4 horizontal gradient of the river’sparameter surface can be temperature used between as Yakutsk an andchanges additional across Tiksi. indicator the of This Lena inter-annual (and andin long-term other September thermal river) 1998 watersheds. relative A tosnow decrease September and of glacial 1995 TCO melt could water be from the mountain result areas of in a thesalinity high Lena for supply measurements River from watershed. of SeptemberSidorov 1997 (1996) and in for 1991, data collected indicates by a Cauwet similarity and between mean values of TCO lowland (Semiletov et al., 1996a, b). ture gradient of the river.near In Yakutsk to early 6.6 September 1998 theperature gradient gradient was in 12 1998 resulted from greater cooling in Tiksi Bay, 6.6 exhibits an extremely high TOC), while(Fig. TOC and 6). TCO Thisthe indicates aquatic that environment, transformation andwatershed, of mineral can carbon be organic considered into carbon quasi-equilibrated theand processes. into organic 7.81 The mineral mean in form carbon pH the insimilar in delta the in and Lena the coastal River middle waters andup of downstream to waters the of 8.01 Laptev the (site Sea,outlets Lena. respectively; 18), Relatively of the in high small value pH the is streams lower river, draining are from similar lakes to in the the pH taiga-tundra zone of the Kolyma and river discharge. Thethe mean major TCO Lena stream76% is of separated the into mean TCO deltabetween channels) was TCO 0.65 mM inis 1998, quasi-homogeneous about with a total mean of 1 tion increases, while is also observed in Kalrix river in sub-Arctic Scandinavia (Ingri et al., 2005). values of total inorganicgest carbon that (CO this variabilityferences is in determined the by Lena changeswater discharge in to (Pipko land et travel hydrology al., fromcharge which 2010). Yakutsk cause (18 800 to dif- About m one the1998 month Laptev (21 is 100 Sea. m required for in For 1995. example, Hence, thecauses this mean opposite appears Lena e to dis- be a dilution e and TOC in river waters, excluding Tiksi Bay, shows a negativenear correlation the ( Lena deltaobtained by at Cauwet the and same SidorovFrench expedition (1996) time SPASIBA-2 in demonstrates (September) significant 1991 inter-annual in within variability the 1995 in framework mean and of 1998 the Russian- with the data the inflow of the Aldanto River and 0.3 mM the Viljuy ( Rivercomparison (Figs. to 1a, 5). a The TCAldan TC of value River. 0.2 increases mM ( Thefrom 0.63–1.07 plot mM (mean of(mean TCO (mean except at site 40) from Stolb Island to Tiksi (Fig. 6). In general, the distribution of TCO primary production (432 mg Cmeasured m in the1991) Lena (Sorokin River and – Sorokin,oasis, 1996). Laptev where Therefore Sea Tiksi the system Bayriver estuarine is in discharge a environment is the summer low. replaces same biogeochemical the month winter (September sea environment when 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 mM, values y) from 2 = 3 2 . Data ob- 10 CO 100 Gt C in 2 p ∼ × 10 ∼ , then total carbon en- 1 − y 3 accumulates beneath the ice 2 was greater than 4000 µatm near 525 km 2 = changes throughout the water column signal from the Lena and other rivers W CO 2 2 p . This suggests that the total carbon added CO 1 p − ), and 2114 2113 1 is equal to the total accumulation of inorganic − 1 that dominates over the temperature shift in the − y into the atmosphere during all seasons. Likewise, 2 3 2 10 18 mg l TC. Therefore, a huge amount of carbon ( ∼ × system in the Lena River-Laptev Sea system shows that ≈ 2 2 was 1267–1579 µatm in Gerasimovskaya and Sinitsina chan- values obtained in September of 2003 and 2004 in the East- data that were obtained in the Laptev Sea, which is influenced 2 over 45 2 1.5 mM ( 2 value increased from 538 µatm in the middle and lower portions ff CO = accumulation beneath the ice was also found in north Siberian lakes 2 p 4 and a decrease in pH (Semiletov et al., 1996b). Maximum is removed from ocean surface waters by photosynthesis, but here the CO 2 p 2 and CH 2 Shelf Seas 0.5 mM, TC = The mean A simple calculation shows that only the Lena River annually brings to the sea a sig- river waters are along-term source hydrochemical of investigations by CO the Russian Arctic and Antarctic Research Here we present CO strongly by inflow of the Lena River (Figs. 9,East 10). of the delta Year-round study of the CO the carbon cycle in the Arcticb, Siberian 2004) seas and (Semiletov, 1999a; in Semiletov thetime et CO central al., basin 1996a, of the(Semiletov, 1999b). Arctic Ocean (Semiletov et al., 2007). Winter- 4.3.2 The influence of Lena River on the carbonate system in the East Siberian cover (Semiletov et al., 1999b).dissolved CO May is a periodwinter of accumulation spring primarily phytoplankton blooms determinestained when the in spring April–May concentration 2002eastern of in part CO the of Buor-Khaya thefrom Gulf river, summer of show (Fig. dramatic the 8a) Laptevwinter, to Sea, when winter OM adjacent (Fig. decomposition to 8b),the dominates, the bottom. when Data fast show ice that supersaturation thickness beneath exceeds the 2.0 sea m. ice is In a principal feature of In winter of 1995 nels, 1045–1500 µatm in Neelovcrease in Bay, TCO and 2140–5800 µatmwere in found Tiksi in Bay May due when to winter OM an is in- oxidized and CO Winter carbon in the Arctic Ocean, 450we Gt C. assume Because of that the total low POC TCO mineral level in and the Arctic organic Ocean, forms)land was to transported the during Arcticstanding the Ocean the Holocene by proportions ( thencarbon of Lena pools “primary River is river and an importantMacdonald, then carbon” 2004; problem to that Alling that the are et is al., North redistributed starting 2010). Atlantic. to to be the Under- addressed main (e.g., Stein and nificant amount of dissolved inorganicTOC and organic carbon; iftering the the mean sea TCO would beby almost Lena 10 Tg River C runo y flowing in the Laptevfrom rivers Sea that and discharge further into the east East-Siberian is Sea. slightlyof high the compared river with toa the 592 µatm corresponding signal in increase the ofcarbonate delta system. TCO and These nearshore resultsof sea. generally the agree Ob and with This Yenisei those rivers increase1991). (Makkaveev, measured 1994), is in and caused in the arctic by mouths Alaska rivers (Kling et al., Yana, Anabar). TCO Siberian Sea and extrapolated to zero(Semiletov salinity et were 0.52 al., mM and 2005).shallow 0.50 mM, East respectively Thus, Siberian assuming Sea the2009), shelf melt we at water can the signal state end is that of negligible hydrological an over summer the integrative (Anderson TCO et al., the contribution from all rivers that discharge into the Laptev Sea (Lena, Khatanga, 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 2 1 − d ) are 2 tot − ranged be- near the en- 2 (Semiletov et 2 1 340–345 µatm). − CO ∼ d CO p 2 p − erent Arctic seas. ff exchange between air 2 has been found (Semiletov ected by photosynthesis es- 2 ff 1.2 mmol m to the atmosphere (Semiletov et CO − 2 p and 1 ) and total dissolved nitrogen (N − tot d 2 fluxes with surface temperature and salinity − ) data show that the surface layer of the east- 2 relative to the atmosphere (Fig. 9); the highest 2116 2115 air 2 2 by photosynthesis is relatively high only in the of the Kara Sea surface waters was higher than 2 2 sources and sinks, while the northern periphery of CO value compared with rivers themselves. The com- 2 p 2 turbulent flux taken in September of 2005 above open CO , while relatively colder and saltier water near the ice and coastal erosion, is a source of atmospheric CO − N) is a source of CO p 2 2 ◦ ff 1.7 mmol m sw 2 CO saturation is not strongly a + p 2 erent waters. CO ff p (Semiletov et al., 1996a, b). The value of = shore (Semiletov et al., 1996a, b). These data show that the ff 2 2 C) riverine plume is characterized by high silicates and normalized export by rivers and aerobic oxidation of coastline-eroded carbon ◦ CO 2 2 p < ∆ and oxygen are a result of OM oxidation and interaction between the concentrations obtained in our data. The measured concentrations of ( 2 2 2 CO CO p ect of CO p ff . Because the uptake of CO ∆ 2 35), while total dissolved phosphorus (P Ice-tethered observations made in the central Arctic Ocean by the Russian North The data show that the sea surface layer influenced by the river is 2–3 times higher The = et al., 2007). The source(Rich of et those high al., values 1997) may and be high may rates indicate of a bacterial rapid respiration turnover of sub-ice DOM which is closely edge is a sink (Semiletov et al., 2007). Pole-33 drifting station intween the 425 summer µatm of and 2005are 475 µatm show larger that with than values a theThe of mean drop photosynthetic summer active to radiation atmospheric 375 µatm (PAR)mid-June value record when in in demonstrated the snow mid-August; near-zero the and values Arctic theseJuly, sea until but ice ( values no began to correlation melt between and PAR reached and its values maximum of value in al., 2007). Measurements of CO water over the Laptev Seanegative shelf (invasion) and values of slope rangedal., between 2007). the positive Comparing (evasion) distributionshows and of that CO warmer andas fresher a water, source which of atmospheric is CO probably the Lena River plume, acts The September 2006 vertical transectfar from the the Lena Lena River signal Deltafresh is to and warm propagated the ( (Fig. north 10). illustratesTA how It values has (nTA), been relative shownS to that the the relatively typical Atlanticalmost completely water depleted in layer the in Lenafluxes plume the yield at a Arctic the mosaic end picture Ocean, ofthe of biological with CO Lena summer. River Vertical plume (up to 80 bined e are responsible for that increase (Semiletov, 1999a, b). North of the delta coastal zone exhibits higher of the Ob and Yenisei riversthat the of water farther o tend to be sinks2008, in 2011; summer Anderson (Semiletov, 1999a, etand b; al., sea Semiletov 2009, exhibits et 2011). a al., spatial-temporal Therefore, 2007; mosaic the pattern Pipko CO across et the al., than di saturation in CO trance of the Kolymawhich River is in close to the the East range(Pipko obtained Siberian et in al., the Sea 2005, same was 2008). area in 716–1779 Data µatm the obtained summers in in of fall fall 2003 1995 and 1994 2004 show that not far from the mouths assume that the level ofpecially CO in the low-transparencyal., water 2011; strongly Semiletov et impacted al., by 2007).zone, the Available influenced data by Lena show that river River the run-oduring (Pipko eastern summer Siberian et and coastal winter, whereas areas of the Laptev Sea remote from the coastline ern Laptev Sea is supersaturated insupersaturation CO was found nearshoals the which delta are and characterizedof over by POC the (Dudarev high Vasilievskaya-Semenovskaya et rates al.,in of 2008), CO bottom perhaps a erosion result and ofdelta elevated surface upwelling waters values of of bottom the water Siberianand enriched rivers decreases (in 10–100 the Lena times River toward up to the 0.1–0.3 shelf g C edge m (Sorokin and Sorokin, 1996), we eteorological Service show that dissolvedtional oxygen to concentrations are inversely propor- dissolved CO physical and biological processestion of as cooling well or as warming, mixing photosynthesis of di and respira- Institute (Rusanov and Shpaikher, 1979) and a continuing study by the Tiksi Hydrom- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 ff CO µM in p export 1 N band storage 4 ◦ 62); both 4 . 0 = 10–10 range as high r , as shown for ∼ . Note, that the ( 2 2 2 concentrations in 2 4 is northward caus- CO the Lena Delta and (up to 5 µM) and an p ff ff 4 15 nM at that time) dur- ∼ supersaturation in the shallow-mid 2 content of shallow shelf water. in the southeastern Laptev Sea; either 4 2 CO 2118 2117 p may be somehow related to degradation of per- , and DOC (Shakhova et al., 2005; Semiletov et 2 4 61) or integrated values of TCO concentrations ranging over two orders of magni- . 0 4 = ) in the Lena River – Laptev Sea system r 4 varied from trace up to 100 nM in the Bykovsky Channel and (Semiletov et al., 1996a, 2004b; Shakhova et al., 2005, 2010a, measurements were taken in the Lena River delta channels in 4 shore waters are generally undersaturated. Macro-synoptical , dissolved CO 4 4 µM in the high Arctic (Lena Delta/Tiksi area) to supersaturation (up to 15 times) induced by oxidation of eroded ff 4 0 2 compared to the atmosphere, up to 1.5–2 fold in summer, and 4–5 –10 2 2 N band, associated with salinities of 31 instead of 34, presumably re- was usually below detection limit (which was , and DOM, follows the Gakkel Ridge towards Fram Strait (Anderson − ◦ 2 4 10 ∼ In contrast, anomalously high concentrations of dissolved CH The carbonate system parameters from all seasons show that the river is super- were measured in some areas of the ESAS (Semiletov, 1999a; Shakhova et al., (Shakhova et al., 2007a). Inobtained an in early the Laptev phase and ofand East these Siberian Semiletov investigations, Seas based (2007) in on found cruises theand a of data integrated significant 2003 salinity and correlation 2004, values betweenthese Shakhova ( integrated features CH characterize marine waterthe as shelf compared from to the riverscan fresh and only water play streams. flowing a onto minor That role suggests for the that dissolved riverine CH episodically dissolved (non-gradually) CH increasing atmospheric mixing ratio of (up to 8.2 ppm) the Subarctic (Kolyma Lowland/Cherskiypermafrost area), rivers which by are numeroussource connected of channels to riverine and the CH through Siberian al., 1996a, taliks, b, 2004b). would That bethe agrees Lena well an with River compared increasing additional with dissolved CH the Ob which is located mostly in a non-permafrost zone Gulf in the southeasternthe part concentration of of CH theNeelovsky delta. Gulf and However, during inwintertime the high the concentrations ice-covered Olenek of season, CH mafrost Channel in (Semiletov, the 1999a). Lena basinriched especially in This dissolved in indicates CH the that faultb). zones and Thaw drainage lakes of withtude thaw dissolved lakes from CH en- The first dissolved CH fall of 1994 (Semiletovdissolved et CH al., 1996a, b).ing summertime: In the the highest Lena concentrations River (50–70 delta nM) the were concentration found in of the Neelovsky 4.4 Dissolved methane (CH son, 1997; Semiletov eting al., 2000) a and northward the extensionSeptember transport of of of 2008 the river by Pipko runo surface etnorthward layer al. transport supersaturated (2011) or of in (b) riverresulting CO the in cyclonic water a pattern decreases decrease dominates of and compared theeastward the supersaturated to propagation surface of the layer the north anticyclonic o Siberianhighest situation, Coastal regional current CO enriched bycarbon CO was found in winter inet the al., nearshore 2004a, zone adjacent 2007). to the Lena delta (Semiletov saturated in CO fold in winter. This resultsshelf in sea, a although narrow zone o conditions of determine CO the distribution(a) of the anti-cyclonic pattern dominates over the Arctic Basin (Proshutinsky and John- et al., 1998).Amerasian This shelf and could Arctic explain Basinwater the (Wheeler concentrations high of et humic al., concentration substances 1996;than of were Opsahl in ten DOM et times 70–85 measured al., higher 1999). over inflecting the a the Surface 87–89 clear signal ofpart terrestrial of carbon the near Transpolar the DriftLena North (Sobek River Pole and propagates from Gustafsson, throughout the 2004). the Lena interior plume Hence Arctic as the basins. influence of the the upper halocline water fromas the 400–600 Chukchi µatm Sea, (Pipko where etvalues values al., beneath of 2002), the may perennial alsoinvolves the play sea-ice. Lena a River role Another plume. indissolved Surface explanation establishing water CO for high from such the Laptev a Sea phenomenon shelf, rich in runo connected with high sea-ice algal production (e.g. Gosselin et al., 1997). Import of 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4 4 1.90 ppm) ∼ atmospheric concentration 4 2 ects on dissolved or- to the Arctic Ocean. ff budget of ESAS coastal 4 4 measurements made in 2006 4 budget in coastal waters. Instead, the supersaturation in the adjacent coastal 2 4 2.10 ppm) found over the ESAS. Taken to- > 2120 2119 . During all seasons the river is supersaturated in 4 production. The Olenekskaya Channel is also un- 4 spot (up to 125 nM) was detected only at the begin- 4 only plays a minor role in the CH in the Lena delta channels may reach 100 nM, but the CH for the ESAS CH 4 4 4 erences in the Lena discharge because a negative correla- ) found recently in the Lena Delta (Ulrich et al., 2009) and ff 1 − d 2 − This work was supported by the Headquarters of the Far-Eastern Branch . and dissolved CH 1 2 − 10 mg m ∼ compared to the atmosphere: up to 1.5–2 fold in summer, and 4–5 fold in winter. 2 The Lena River is characterized by relatively high concentrations of primary green- Transformation of riverine organic carbon into mineral carbon, and mineral car- Program of theGunter Nordic Weller, Council Syun of Akasofu, Ministers Gueorgui (331080-70219). Golitsyn and We Larry thank Hinzman Valentin for Sergienko, their support of our Acknowledgements. 06-05-79080, 06-05-96064p, 07-05-00050a (IPS),64213, No. 08-05-00184a 08-05-00191a (IIP)), (NES), the and Swedish No. Polar 05-05- Research Secretariat, and the Arctic Co-Op This results in a narrowsea. zone of Spots significant of CO dissolved CH concentration decreases to 5–20 nM towardsof the sea, riverborne which export suggests of onlyseabed a CH minor appears role to be the source that provides most of the CH of the Russian AcademyUniversity of of Alaska Sciences Fairbanks, and (RAS), theCooperative Cooperative the Institute Agreement for International Arctic NA17RJ1224 Arctic Research with throughsearch Research NOAA was the Center funded University of in of part the OPP-0342837 Alaska by (IPS)), the (IPS and US and National by NES). Science the Foundation This Russian (grant re- Foundation OPP-0230455, grant for Basic Research (No. 04-05-64819, shift of aboutSea). one month Increasing is theganic required Lena and River for inorganic discharge water carbon: causesdecreases. to TOC opposite concentration Total travel carbon e increases, from entering whilealmost Yakutsk the TCO 10 Tg to sea C with the y the Laptev Lena discharge ishouse estimated gases: to CO be CO bon into the organicequilibrated processes. form Significant in inter-annual the variabilityand in Lena their mean sum River values of (TC) watershed, TIC,hydrology has TOC, can which been be cause found. di considered Thistion a variability may is quasi- be determined found by between changes TC in land in September and mean discharge in August (a time the annual input of eroded terrestrial carbon onto the ESAS, which is about 4 Tg. 5 Conclusions The Lena River integrates biogeochemicalsignal signals reaches from far out its over vast themay drainage Arctic be basin Ocean. and equal The its to annual(1994) Lena 0.38 statement Tg River concerning discharge (moderate the of to precipitation POC marginal of high “filter”, 85–95% estimate). then of only total about If PM 0.03–0.04Lena (and we Tg POC) River. of instead on POC The the accept reaches Lena’s the Lisytsin’s POC Laptev export Sea from would the then be two orders of magnitude less than along the Lena Rivervs. channels moderate which (1.95–2.10 demonstrated ppm) relatively andgether, low riverine high values export ( of ( CH waters. conducive to early diageneticderlain CH by a faultpermafrost-associated zone which hydrates may (Collett allow andtov, the Dallimore, 2007; formation Shakhova 2000; of et Shakhova al., throughamong 2010a, and taliks, b). other Semile- disturbing However, Lena the in Delta theconcentration Bykovsky channels) downstream. Channel we This (the picture detected deepest is a furtheremission drastic consistent ( with decrease low in CH dissolvedour CH high-precision (Shakhova et al., 2010a, b) air CH nels in early Septemberfrom 2006 Yakutsk (Shakhova to et thein al., Fig. Laptev 2010a, 11. b) Sea andning in The along of the dissolved the the late CH Lena Olenekskayaa Channel River August–September huge (Fig. of amount 3), 2008 where of are ice-complex eroded bank shown OM, erosion forming provides the anaerobic bottom environment which is 2007b, 2010a, b). Results of high-performance studies made in the Lena Delta Chan- 5 5 15 25 10 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ¨ O.: ¨ orth, C. 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Yu.: Plankton and primary production in the Lena River estuary 5 5 30 25 15 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 , km erent years. W ff TOC, + ) in August of di 2 W , TCO 2 CO p , mM TOC, mM TC, mM 2 , TC obtained along the Lena River stream (from 2132 2131 2 Yakutsk – Stolb Is. , TOC, Si, 2 The Lena Delta – Tiksi Bay mM mM µM µatm mM TCO 25 pH CT 12 7.943 7.904 0.92 7.795 0.75 0.46 7.786 0.78 0.59 7.67 91.07 0.64 0.45 7.57 89.98 0.66 479 0.57 7.66 85.99 0.66 428 0.75 7.68 90.3 0.66 569 0.89 7.67 88.2 0.65 486 1.38 0.93 88.4 0.63 577 1.34 0.69 83.4 727 1.23 0.63 82.4 613 1.21 81.7 575 1.41 568 1.55 1.59 1.34 1.26 2324 7.8325 7.8626 0.90 7.8527 0.84 0.40 7.8628 1.03 0.53 7.87 72.129 0.99 7.75 71.430 0.99 540 0.38 7.8531 1.01 470 0.38 7.82 63.932 0.95 71.1 0.38 7.8733 0.93 544 1.30 0.39 7.78 52.5 589 34 0.98 1.37 0.39 7.82 52.535 0.94 717 0.40 7.76 52.5 52036 1.04 534 1.37 0.40 7.8337 1.14 551 0.42 7.81 52.538 0.96 1.39 0.45 7.81 63.939 1.37 0.96 609 1.34 0.39 7.78 41.3 52640 1.16 608 1.32 0.47 7.78 38.741 1.36 715 0.38 7.75 43.8 1.25 523 1.34 0.43 7.79 52.5 1.38 1.38 513 1.46 0.47 47.2 1.32 593 1.59 1.30 37.4 688 1.35 31.5 585 1.43 682 1.54 35.0 1.79 1.72 736 2.68 1011 7.7812 7.8113 0.82 7.8414 0.75 0.75 7.9015 0.84 0.63 7.94 85.716 1.00 0.58 7.96 81.617 1.07 597 0.47 7.95 80.818 0.99 499 0.67 7.95 78.819 1.01 532 0.52 8.01 80.820 1.02 558 1.57 0.48 7.95 77.021 0.95 558 1.38 0.43 7.86 77.022 1.06 474 1.42 0.56 7.80 85.8 0.92 494 1.47 0.58 7.81 74.6 0.93 498 1.74 0.43 77.0 0.93 380 1.51 0.52 487 1.49 0.39 72.4 1.45 72.3 611 1.51 522 593 1.64 1.45 1.35 1.32 N Mean 7.81 1.06 0.47 51.8 592 1.51 Mean 7.83 0.85 0.59 82.1 538 1.44 Major components of the carbon cycling and silica sampled between Yakutsk, the Mean concentrations of TOC, TCO TimeSeptember 1995September 1998September 1991 (SPASIBA-2) 0.60 0.95 0.60 0.65 TCO 1.20 0.53 0.58 62.94 1.42 1.24 50.35 56.51 Yakutsk to the Laptev Sea), and the Lena River discharge ( Table 2. Lena Delta and Tiksi Bay (late August–early September 1995). Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

the Laptev 1, (2) 1–1.3, (c) < 10, (2) 10–20, < : (1) 1 : (1) − 1 −

) b 2134 2133

the Lena River stations, late August–early September (a) Lena River stations, September 2003 and 2008;

PM distribution in the surface layer, mg l POC distribution in the surface layer, mg l (b) (b) (c)

a) ) 1.6. 30 and 1 Figure c > >

Distribution of sampling sites in the Lena lower stream-delta channels in the late 2 Figure Map of the study area location: (3) 20–30, (4) (3) 1.3–1.6, (4) Fig. 2. (a) July–early August 2003; Fig. 1. Sea stations, Septembermarked 1997, by 2005, yellow (Bykovsky 2006green Channel), and (Tumatskaya Channel), blue April and (Malaya red and 2002. (Olenekskaya Bol’shaya Channel) Trofimofskaya colors. Channels), Location of major channels is 1995 and September 1998; Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ): 1 −

25, (2) 25–50, (3) 50–75, < particular materials (PM, mg l (a) 40%, (2) 40–69%, (3) 69–98%, (4) 98– < 2136 2135 CTOM of POC (%) (1) (b) 24; >

4 Figure Distribution in the ESAS surface sea water of: CTOM (%) in the ESAS surface sediment: (1) 3. Figure 2, (2) 2–13, (3) 13–24, (4) 75. < > (4) Fig. 4. (1) Fig. 3. 100%. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 , silicates 25 TOC TCO2 TC ), pH 2 (TCO 2 41 39 37 41 41 41 41 41 35 ) along the Lena River from Yakutsk 37 37 37 37 2 37 33 33 33 33 33 33 31 CO 29 29 p 29 29 29 ( 29 2 25 25 25 25 25

27 21 21 21 21 21 25 Station

17 17 17 17 17 2138 2137 23 13 13 13 13 13 21 9 9 9 9 9 Station 19 5 5 5 5 5 17 1 1 1 1 1 8 1 1

80 60 40 20

8.1 7.9 7.8 7.7 7.6 7.5 1.6 1.4 1.2 0.8 0.6 0.4

800 700 600 500 400 300

0.8 0.6 0.4 0.2

100

M m Si, 2 25

atm m , pCO pH 2

TOC, mM TOC, 15 mM , TCO 13 11 Figure 5 Figure 9 7 5

6 3

1

1 0 3 2

Figure

1.5 0.5 2.5 mM Distribution of measured total organic carbon (TOC), total CO Distribution of measured total organic carbon (TOC, mM), total inorganic carbon (TCO Fig. 6. mM) and total carbon (TC, mM)early along September the 1995). Lena River stream from Yakutsk to Tiksi (late August– Fig. 5. (Si) and calculated partial pressure ofto dissolved Tiksi: CO stations(from 1–22 Stolb (from Island Yakutsk to downstream the Laptev to Sea), the late delta, August–early September Stolb 1995. Island); stations 23–38 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

) vs. S 2 35 30 25 20 wintertime distribution (April 2002) and tran-

S (b) 15 2140 2139 10 (µatm) profile across the Buor-Khaya Gulf of the Laptev Sea: 2 2002. CO (d) p 5 TCO2, Dunay TOC, SPASIBA-2 TCO2, SPASIBA-2 1997,

7

(c) 0

Figure

0.0 2.0 1.5 1.0 0.5 2.5 mM Meridian vertical

The mean values of total organic carbon (TOC) and total inorganic carbon (TCO summertime distribution (September 1997); sects position in (a) Fig. 8. measured in September 1991 (adoptedonboard by HV Cauwet Dunay. and Sidorov, 1996) and in September 1997 Fig. 7. 8 Figure Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

, ), 1 tot −

, %) within the south-north 2 C), salinity (S), total alkalinity (TA, mmol kg

◦ , T 2142 2141 ), silicates (Si, µM), total dissolved phosphorus (P 1 − , µM) and oxygen saturation (O tot (µatm) between the surface water and atmosphere in the Laptev 2 CO p ∆ Vertical distribution of temperature (

Distribution of transect across the Laptev Sea, September 2006. normalized total alkalinity (nTA, mmol kg µM), total dissolved nitrogen (N Fig. 10. Fig. 9. Sea, September 2005. Figure 9 Figure Figure 10 Figure Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

2143 (nM) in the Lena River, September 2008. 4

11 Figure Distribution of dissolved CH Fig. 11.