Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2 − and 2 , results 2 erent sig- ff , 1 mol C m . All of these 4,5 ff ∼ Discussions contribute to a 2 Biogeosciences 500 000 km gC. Even though mi- ∼ to CO 12 4 10 × , N. Shakhova from the Laptev Sea and an 4 ff , I. Pipko mol C or 6 1,3 12 shelf water inventory as minor sources. The 10 ¨ om 4 1138 1137 × 5 ), was observed in very high but variable con- . 4 1 ¨ om as well as oxidation of CH 2 ) over-saturating all waters from the surface to the bottom 2 , S. Jutterstr ˚ ahlstr 2 ¨ ork illustrating the dominance of marine primary production. The 2 , and I. W , G. Bj 1 4,5 This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Department of Chemistry, University ofDepartment Gothenburg, Sweden of Geosciences, University ofBjerknes Gothenburg, Centre Sweden for Climate Research,Pacific UNIFOB Oceanological AS, Institute Bergen, FEB Norway RAS,International Vladivostok, Russia Arctic Research Center/University Alaska, Fairbanks, USA decay of organic matter to CO surface where the majority ofare organic added matter to ends the up,low bottom and oxygen water. most and of High pH the nutrient were decaymatter observed concentrations products decomposition, in and the fugacity methane bottom of (CH centrations. waters. CO Another This signature is offrom due organic ancient to organic its matter, seabed becomingformation sources available of of due so-called glacial to taliks sub-sea originRiverine (layers permafrost of or transport thaw thawed modern as and sediments production wellfresh within water as the systems leakage permafrost could of body). add to groundwater the rich CH in methane from decay in with respect to CO drawdown of dissolved inorganic carbon equalswhich a when primary multiplied by production half of in the area an of annual the East primarycrobial Siberian decay production Sea, occurs of through 0 much of the water column it dominates at the sediment natures. Sea ice formationmajor during impact the on winter physical as season well andwater as melting biochemical mass conditions. in distribution The the internal summer isThe circulation has and significantly western a region influenced is byextensive dominated input the by of atmospheric terrestrial input pressure organic ofproduces matter. field. carbon river The dioxide runo (CO microbial decay ofrelative this to atmospheric organic values, matter even ifshowed the recent nutrient primary concentrations production. of the The surface waters eastern surface waters were under-saturated Shelf seas are amongEast the Siberian most Sea active biogeochemical isthe marine Atlantic a and environments prime Pacific and example. Oceanswaters the and contribute has This chemical a constituents, sea substantial dissolved is input and of supplied particulate, river but by runo of seawater di from both Abstract I. P. Semiletov 1 2 3 4 5 Received: 18 January 2011 – Accepted:Correspondence 19 to: January 2011 L. – G. Published: Anderson 8 ([email protected]) FebruaryPublished 2011 by Copernicus Publications on behalf of the European Geosciences Union. Biogeosciences Discuss., 8, 1137–1167, 2011 www.biogeosciences-discuss.net/8/1137/2011/ doi:10.5194/bgd-8-1137-2011 © Author(s) 2011. CC Attribution 3.0 License. East Siberian Sea, an arctichigh region biogeochemical of activity very L. G. Anderson 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | for the 3 ected by the ff is also added ff ). promotes development of the fresh Siberian 1140 1139 ff for the period 1936–1998 and 102.7 km 3 ected by intrusions of warmer Atlantic water coming http://rims.unh.edu/ ff 100 km outwards. The Western area is strongly influenced by ∼ , but as the mean depth is only 52 m it has the smallest volume after 2 km and by wind. The river runo 3 ff 10 × (mainly from the Lena river) before entering the ESS. River runo ff The information on the biogeochemical environment of the ESS is limited, but some The temperature is generally close to the freezing point over the entire water column The current system in the ESS is controlled both by the strong baroclinic forcing by The fresh water content of the ESS is high, especially in the western area (Steele the coast and up to from the shelf slope during upwelling conditions (Dmitrenko etstudies al., 2010). have been performedcluded that along the the nutrient coast. distributionpiration was of organic impacted Codispoti matter by and and summerhigh the primary Richards origin nutrient production, (1968) of res- concentrations, the con- high mainlyPacific salinity through phosphate, bottom the water. they Bering Based suggested on Straittov the was that et the inflow al. source from of (2005)and oceanic the divided geochemical water the data to from ESS the ESS. the into Semile- sediment two surface specific collected areas in based an on area water reaching properties from is illustrated in Fig. 1. during winter astemperature a raises result to of severalThe surface degrees bottom above cooling layer zero and may near well ice the be formation. surface a in ice During free summer areas. the which makes the ESS highlycoast variable. under The cyclonic SCC atmospheric was conditions focusedwith in as anticyclonic the a atmospheric summer-fall narrow circulation of jet it 2003, alonget was while the al., less in 2008) confined 2004, and as was reportedal., not by 1999). present (Savel’eva at The all SCC in oftenthe extends the all Chukchi northward the Sea flow way east into from of theseawater ESS Chukchi the from (Weingartner Sea, Bering et where the Strait. it Chukchi mixesCodispoti with Sea, Between and with the Richards, its SCC 1968). high and A nutrient the map signature, Wrangel of enters the Island the ESS with ESS the (e.g. most common current field to a largely ice free area (Nghiem et al.,river 2006; Kwok runo et al., 2009). Coastal Current (SCC) following theet coast al., from the 1999). west to However, the the east wind (e.g. Weingartner forcing has a strong impact on the current system the ESS. From being an area largely ice covered even in the summer it has changed and Martin, 2001). Theobserved large decrease during in the the latter summer years sea has ice also coverage had that has a been major impact on the ice conditions of of having less fresh water insure the in eastern the part central duringsituation Arctic summers (cyclonic with (anticyclonic dominant circulation) circulation) high (Dmitrenko and pres- etcant vice al., long versa 2005; term for Dmitrenko changes the et ofhas low al., the been pressure 2008). freshwater explained content Signifi- by asmospheric variations seen circulation in in (Polyakov et river the al., discharge historical 2008).wind data combined The pattern record with sea resulting ice changes in motion that in isa the also the ice near a at- generally shore moves in zone the during wind winter direction with except within stationary land fast ice (Morris et al., 1999; Holt and Ermold, 2004), butwind its and momentary is spatial controlled distribution by the is atmospheric largely pressure dependent pattern. on There the is a clear tendency mean annual discharges ofperiod 50.6 km 1978–2000, respectively ( 1 Introduction The East Siberian Sea (ESS)of is the 895 widest of thethe Arctic Chukchi Ocean Sea shelf (Jakobsson, seas, 2002). withseawater an From of area a Pacific hydrographic point origin itfrom entering is the from a west. transit the However, area especially eastruno with the and latter water waters of havedirectly been Atlantic heavily origin into diluted entering the by river ESS, where the major rivers are the Indigirka and the Kolyma with sulting in under-saturation of allareas the of bottom under-saturation waters down withcalcifying to respect organisms to 50% are aragonite with very and unfavorable. respect large to calcite. Hence, conditions for natural ocean acidification making the saturation state of calcium carbonate low, re- 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 K . 1 − ). 1 µmol kg , possibly increasing ∼ 2 1%. Oxygen was determined www.licor.com ∼ CTD system was attached to a + C and atmospheric pressure. ◦ 003 pH units and the accuracy was set , with the accuracy set by calibration . 1 0 − ∼ 1142 1141 2 µmol kg ∼ ) was computed from pH and total alkalinity using the soft- 2 CO f ( 2 determination are given in Shakhova and Semiletov (2007). 4 , (Haraldsson et al., 1997) with the accuracy set the same way as for 1 − 2) used were those of Roy et al. (1993) as they show the best internal consis- were determined using the open-cell Licor7500 ( K 2 The fugacity of CO For methane measurements water samples were immediately taken from Niskin bot- DIC was determined by a coulometric titration method based on Johnson et In the summer of 2008 (15 August to 26 September) the International Siberian Shelf 2 µmol kg CO phases was applied (Semiletov etwith al., a 1996). MicroTech-8160 gas Methane chromatograph concentrationstector. (GC) were The measured equipped standard deviation with of a duplicateDetails flame analyses of (3–5 ionization the replicates) de- CH was less than 5%. under the EU project Europeanf Project on Ocean Acidification (EPOCA). Atmospheric tles and poured into replicate 500-mlple. glass bottles, The overfilling 1.5–2 headspace times with technique the for sam- equilibrating between the dissolved and gaseous Lee and Millero, 1995), having aby precision the of equilibrium constants of thescale indicator. and The are values normalized presented are to on a the temperature seawater of 15 ware CO2SYS (Lewis and Wallace,and 1998). The carbonatetency dissociation in constants the ( low temperature watersor of TA the as Arctic input Ocean parameters. when using The any data two of are pH, archived DIC at the PANGEA information system al. (1987), havingagainst a certified precision reference of materialstion (CRM), of Oceanography supplied (USA). by TA∼ was A. determined Dickson, by Scripps potentiometricDIC. Institu- titration, pH precision was determined by spectrophotometric detection (Clayton and Byrne, 1993; using an automatic Winkler titration system, giving a precision of for station locations12 see bottle Fig. rosette 2a. systemagainst for water water samples A sample analysed SeaBird onboard collection. usinghalf 911 an The of AUTOSAL lab-salinometer salinity the on data about collectedkalinity was water (TA) calibrated and samples. dissolved inorganic Depthcontainer carbon profiles laboratory (DIC) of were on nutrients, collected boardphosphate, oxygen, and using determined pH, nitrate state in total and of a al- silicateScientific the Instruments were art Inc.). determined analytical by techniques. Theby a samples a Nutrients, were SmartChem 6 filtered analyzer to before (Westco 8-points analysis calibration and evaluated curve, precision being 2 Methods 57 stations were occupied in the ESS between the 31 August and 15 September 2008, Study (ISSS-08) was conducted withmation the of objective carbon to from investigate landArctic the over Ocean. the flux shelf and An seas transfor- extensivevessel and sampling Yacob into Smirnitskyi program the in was deep the undertaken watersThis central on of basins study board the of the Laptev, of the East Russian thebiogeochemical Siberian data and East and Chukchi Siberian in Seas. thising Sea contribution relevant we is biogeochemical analyze processes, by including them the with farand magnitude the the the of aim decay primary most of of production, elucidat- organic comprehensive matter collection as well of as its impact on ocean acidification. Pacific derived water. FurthermoreESS the has waters been in showndue the to to be western added a near input strong shore2005, of source zone 2008; terrestrial of of Semiletov organic atmospheric et the matter al., CO from 2007; permafrost Anderson et thawing al., (Pipko 2009). et al., Lena River input from the Laptev Sea and the Eastern area is under direct influence of 5 5 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | − 3 25) > shore ff 2HCO → close to the 2 O T , e.g. the Lena + reported for wa- ff 1 − (s) from the Lena River 3 ff E, indicating an inflow ◦ C in the top 1 m layer in CaCO ◦ set at zero salinity of about + ff 21 µmol kg ± O(org) E), with no clearly represented SCC 2 ◦ is a result of hydrogen carbonate ions ff N in the west with salinities in the range of ◦ 1144 1143 set is close to the 570 ff shore and also inhibited development of a confined SCC. This ff also impacts the chemical signature of the waters as it has a high con- (Fig. 6a). This o plot (Fig. 5). The waters at freezing temperature have salinities around ff 1 S − - T (e.g. Anderson et al., 2004). The linear fit of TA versus salinity is a result of the + 2 The temperature distribution at the bottom shows a large region with The summer of 2008 was characterized by persistent high pressure systems in the Ca oxygen concentrations (signature of microbial decay of organic matter) (Fig. 6b). the drainage basins, according to the reaction+ CH relatively conservative behavior of TA, i.e.tion the and small decay impact of on organic TAand matter by in biological dissolution oxic produc- water of (Fig.other 6a). calcium hand It carbonate further shows is implies a thatconcentrations less not formation on conservative the very behavior low (larger abundant side deviationtions of in from a (signature mixing the a of line linear primary ESS. associated fit) production) with DIC with and high on oxygen higher concentra- concentrations the associated with low as well as nutrientsshows (e.g. a Gordeev clear et linear al.,500 µmol 1999). relationship kg with The salinity ISSS-08ters with with TA a data an salinity from over o 24Anderson, the from 1997). the ESS Laptev and The East TAfrom Siberian content Seas a in in combination the 1994 of (Olsson runo decay and of organic matter and dissolution of calcium carbonate in seen in a 32–33. 3.2 Biogeochemistry The river runo centration of total alkalinity (e.g.Pipko Anderson et al., et 2010), al., dissolved 1983; organic Yamamoto-Kawai et carbon al., (e.g. Anderson, 2005; 2002; Pipko et al., 2010) River plume thatthe heated Dmitry the bottom Laptev(Shakhova sediment Strait and Semiletov, to inducing 2007). up the Theabove freezing to bottom thermal as waters 3 these abrasion at have the aet of continental signature al., frozen of slope 2010). warm are The seafloor Atlantic well high Layer deposits temperatures water in (e.g. the Dmitrenko waters of low and high salinities are clearly above zero degrees. This has been explained by heating from runo freezing point. Only the waters closest to the coast line to the west are significantly is reflected in the hydrographicalin data the which generally eastern show part high ofin surface the the salinity ESS ( surface (east water of salinitysalinities about in of 160 the near southeastern 30 ESS. closefrom There to the are the Chukchi even coast Sea. some at Alternatively enhanced (depth longitudes these around 160 waters 30 have to m), been 170 but mixedthere if up is this from a was the clear the bottom signature caselow of nitrate it primary and must production, phosphate have i.e. been concentrations. oxygen super-saturation early as in well the as season as Beaufort Sea and Wrangelwind Island over area the (Fig. ESS.September, 4) A when notable which the period resulted observations of inwinds near very over generally the a strong southerly month Kolyma southerly prior Rivermost winds to of were the was the made. expedition river around as water 2–5 o The well as o under the expedition likely forced observed during the cruise andfield restricted shows generally the low sampling surface program salinitieslow in (Fig. salinity the 2b). water west The from and high salinity the(about in Laptev the 4 Sea, east a times (Fig. result 3). higherthe of The than Siberian the coast large the and runo sum is20–25. of seen The all Indigirka bottom up and waters tosame Kolyma), 75 in range. enters the The shallow the surface southwestern water ESSwater part temperatures to along show the have a southwest low similar and salinities pattern the of coldest with the to the the warmest northeast. 3.1 Hydrography The sea ice coveragethe in ESS the could summer be of sampled 2008 (Fig. was 2a). fairly Only favorable some and small a patches of large drifting area sea of ice were 3 Results and discussion 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 | values (at 2 25, the other 23, is found in CO = f ∼ S at 1 − 1 µmol kg shows that heterotrophic activity 2 130%, is observed at about 20 m ∼ ∼ values. The lowest 20, there is a signal of nutrient con- 2 ∼ CO f is at or above the atmospheric values at the 1146 1145 2 CO f 32 show much more diverse signatures, with a wide ∼ 32) are mostly found in the surface and sub-surface wa- ∼ values relative to those at atmospheric equilibrium, indicat- 2 below atmospheric values, and salinities between 25 and 32 2 CO signature is that microbial decay of terrestrial organic matter, low 27 and f 2 color coded for salinity (Fig. 8c) confirms this and shows that these ∼ CO 2 f as well as nutrients. The very low salinities, below CO 2 f CO f even if it has no phosphate. The most plausible explanation of the pattern . At the low salinity waters, below ff ff versus salinity (Fig. 7). A common feature for these parameters is the high 2 . The nutrient consumption is most pronounced for phosphate as the observed 2 In the salinity range of about 27–32 there is a signal of draw down of phosphate in Waters having salinities below In marine waters the phosphate and nitrate concentrations will normally increase Biogeochemical transformation is even more obvious in plots of the nutrients and The oxygen saturation in the surface waters with a deficit in DIC are typically between 40%, and these waters were found close to the bottom. However, no water samples CO conditions are confined to thelization upper (AOU) (Fig. 30 m. 8d) supports The this color conclusion coding by for its Apparent negative Oxygen AOU Uti- values for waters these waters. 3.2.1 Primary production The waters with (Fig. 7d) aretions the are only found ones indepth where plot the net of surface autotrophic waters conditions of prevail. the northern These and condi- eastern ESS (Fig. 3a). A on board the Yacob Smirnitskyi,in but the some laboratory. samples The werethis quality brought contribution. of home However, these the and data majority analyzed centrations was of not the at samples good the from and detection the isin upper limit, this thus waters indicating depth not had range. that con- presented Hence ammonium in nitrate was is of the minor limiting factor importance for marine primary production in in nutrient and in nutrients, is dominatingtransformation (Anderson over et marine al., primary 2009). production when itthe comes waters to with low carbon ing primary production. Formany nitrate samples this with feature is closenitrogen less to source obvious, zero in largely primary concentration. because production. of Ammonium the Unfortunately can ammonium also was be not determined used as a sumption by marine primary productionCO and the water isconcentrations oversaturated cannot with be respect achieved to bybeing mixing seawater of with the a twobeing phosphate observed runo concentration water masses, of one river runo tion (Fig. 7a–c) since the concentration in this area also is impacted by the mixing with salinities between ters to the north andconsuming east CO of the ESS.the This southwestern is a region. signature Here oftime the recent of primary the production, studymunication, which December were 2010). in Oversaturation the ofexceeds range that CO 375 of to autotrophic 380 in µatm these (A. waters. Salyuk, personalwhen com- heterotrophy dominates, but this is not directly reflected in the nutrient distribu- have significantly lower nutrient concentrations,of all Atlantic origin consistent circulating with along these the(Rudels continental waters et slope being al., of the 1994). deep central Arctic Ocean span of nutrient concentrations as well as were collected directly atlower the oxygen sediment saturation – values water than the interface observed and were thus present. itf is likely that even values in the salinityThese range high values 32–33, are a the signalsediment of range mineralization surface with of with organic near the matter, likely freezing decayThe occurring products water at highest released the temperatures. salinities to are the found cold in bottom the water deep (Fig. water 3d). at the shelf break stations and they 100 and 110%, butdepth. higher This subsurface oversaturation, maximum in upand oxygen to saturation Richards was (1971), also which observed they bystratified Codispoti attributed waters. to in The situ< oxygen photosynthesis production saturation in in well the waters of excess DIC was as low as 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 is valid release 2 4 − for waters being 1 − E. In the same region the lowest ◦ and TA, yields a consumption of T , gives an annual primary production 2 , is integrated over 30 m depth it results S 1 − N and 155 when it passes through the upper sediment ◦ of phosphate and nitrate, respectively. These 1148 1147 . This consumption is restricted to the area 4 2 1 − − 500 000 km ∼ gC that was suggested by Sakshaug (2004). How- C signature of OM in the particulate material, POM 12 13 gC, which is about one half of the previous estimations: 10 δ in the bottom water occurs, it is caused by CH 12 × 4 values are observed. However, the highest nutrient concen- 10 . The nutrient signal is less straight forward (Fig. 8a and b), . Nitrate on the other hand is very close to zero for these wa- 2 2 2 25, which according to the surface salinity map (Fig. 3a) is × and 5.3 µmol kg ∼ CO CO 1 to leak up into the bottom water methanogenesis rates need to be CO f f − profile it is seen that the minimum value is about 175 µatm that f 4 S > 2 CO gC (Vetrov and Romankevich, 2004; Vinogradov et al., 2000) and sub- . Applying the Redfield ratio of P:N:C of 1:16:106 means a consump- mol C or 6 f 1 12 itself is used as electron acceptor. In marine environment modern methano- − 12 2 10 10 × × 5 . Another possible product of microbial decay of organic matter is methane (CH When a DIC consumption of 35 µmol kg From the saturation of dissolved CH or in the anaerobic2005). lenses In that the might ESS, at suchlated places production above occur is the limited in sub-sea to themodern permafrost, the pycnocline methanogenesis Holocene which can (Damm sediment caps only et layer take deeper accumu- ential al., place sediments. sediment within the accumulation, This taliks primarily means and/orin in in that order areas water for of depths this prefer- CH greatervery than high 50 m. as anaerobic Moreover, can oxidation be of up CH toWorld Ocean 3–7 provide orders such of rates magnitude of (Reeburgh, methanogenesis; in 2007). most situations Very where few super- locations in the et al., 2005), andtransect molecular (Vonk and et radiocarbon al., in 2010). the POM along the Kolymawhen CO paleoriver genesis can occur in strictly anaerobic sediments, where sulfate concentration is low, trations are found inslightly other to regions. the north Thein maximum of a phosphate the region concentration region inare is of the also found eastern the observed. ESS. minimum This Intrial oxygen organic over the and matter all latter pH (low pattern region values, inof is nutrients) the as marine likely dominates highest well in the organic nitrate as the result matter concentrations pattern western that (OM) ESS, is degradation while dominates of degradation supported in terres- (Dudarev by the et the northern al., and 2011, eastern this issue) ESS. and Such in a the sediment (Naidu et al., 2000; Semiletov The fate of organicseen matter in and the and bottom itsobserved waters impact in of a on the region the ESS centered atpH chemical (Fig. about and 9). environment 75 the is The highest clearly lowest oxygen concentrations are 3.2.2 Fate of organic matter of the ESSabout with half of thefor ESS. half of Assuming the that ESS,of an with 0 annual an area consumption of of10–15 1 mol C m stantially lower than theever, 45 his estimate wasassumptions not from based the surrounding on seas. any data from the ESS, but was made only on alistic consumption. However, the exactproductivity nutrient started concentrations are in not these known watersdown and before from thus nutrient it data. is not possible to prove thisin carbon a draw consumption of about 1 mol C m eastern ESS. gives a maximumunder-saturation under-saturation is 100 µatm of andsumption about using in this 200 µatm. value DIC, to35 using µmol compute kg the the Assuming corresponding observed that con- tion mean of the 0.33 µmol kg mean values are in the range of all data in the top 30 m of Fig. 8a and b, making this a re- with phosphate concentrations inunder-saturated in the range ofters. 0.7 However, there are to upper 1.2 watersin µmol (shallower kg both than 30 phosphate m) with and higherin nitrate, concentrations the as southwestern well ESS. as It lower is in clear, phosphate, though, but that these nitrate are all is found the limiting nutrient in the of under-saturated 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 | N ◦ and Ω = con- ff 4 are as- 4 E. This is il- E, and along ◦ ◦ . Omega will be fur- relative to the atmo- 3 4 concentration is mostly E and 165 ◦ 4 E and 160 ◦ is not determined by water 4 determined in 2008 are similar to those 4 in the East Siberian Arctic Shelf, including that has a lower calcium ion concentration 4 ff 1150 1149 concentrations measured so far in the ESS, up 4 sources inside the fault zones and through taliks cannot be concluded from these data. However, E. These huge clouds of dissolved CH ◦ 4 2 release most likely due to ebullition from the seabed is the chemical solubility of CaCO 4 SO E to 170 K is (Fig. 10a) with the largest contrasts in the frontal zone be- ◦ concentrations, up to 35–45 nM (Fig. 9f) were found in the 2 4 CO f ) where concentration between the years 2003 and 2004 was very high, up erent biogeochemical processes dominate, with heterotrophic activity 4 SO ff K ]/ concentrations were found in September of 2003 (Shakhova et al., 2005). − 4 2 3 ] [CO + 2 the Kolyma Delta (Shakhova et al., 2005). However, more constant high CH If the situation has been like this for many years or if it has been “acidified” during In the ESS methane is found in highly variable concentrations. At some areas of ff one in the easttwo that regimes is di dominated by modified water from the Pacific Ocean. In these increased the load of terrestrial OM adding to the acidification. 4 Summary and conclusions In this contribution aa comprehensive data large set area of offormation physical the that and East occurs chemical Siberian in data, Sea, this covering regimes illustrate region. exists, the The substantial one data biogeochemical in confirm trans- that the two west governing that hydrographic is dominated by an influence of river runo later years as a resultatmospheric of partial both pressure an of increasedin CO load a of terrestrial shallow OM seawithin as like well a the as ESS very increased thebeen short worsened atmospheric during time, signature the maximum will last decades. penetrate a Likewise, to few thawing the of years. the bottom permafrost likely Hence, has the conditions have likely ther decreased by dilutionthan with that river of runo seawater. Theseof conditions have calcite a and profound aragonite impact in onstrongly the the under-saturated bottom saturation with state waters respect of tothe the both area ESS calcite (Fig. investigated and 11). during aragonite.and the The Most western close ISSS-08 of part is the to is rest under-saturated saturation of conditions with or make respect slightly the to under-saturated living aragonite also conditions for with benthic respect calcifiers to very calcite. unfavorable. These The low pH causedsolved by carbonate microbial system decay from ofcrease carbonate organic the ions matter solubility to results state[Ca carbonic in of acid. a calcium drift carbonate, This of typically in the expressed turn dis- as will omega de- ( 3.3 Impact on ocean pH located in the southeastern part of the Laptev Sea. to 900 nM, were found inlatitude 2008 transect at from the mid-shelf 155 sociated beneath the with pycnocline the along massive thein 74 CH the East Siberianin dissolved Shelf CH (Shakhova etto al., 3–4 times 2010a in ando some b). particular areas Note includingcentrations that the have the been shallow found variability alongshoreto over transect the 760 east nM last 5 in yr summer) at and the hot Svyatonosko-Belkovsky spots (up in to the 220 Ust’ nM) Lensky fault (up zones, both related to the location of(Nikolsky seabed and CH Shakhova, 2010; Shakhovaas et high al., CH 2010a andIn b). general, In the the concentrations of latter dissolvedmeasured area CH in twice 2003, but the highest CH maximum dissolved CH bottom water along thethe Indigirka shallow paleo-valley, transect between east 150 oflustrated in the Fig. Kolyma 10b mouth, where betweenmass the circulation, 160 distribution as of dissolved CH tween the low saline andproductive low-transparent and heterotrophic high-transparent local Pacific-derived shelf autotrophic waters2008, waters and 2011; (Pipko the Semiletov et high et al., 2005, al., 2005, 2007). The dissolved CH view of possible sourcesthe of ESS dissolved was CH recently published (Shakhova et al., 2010b). the ESS surface watersphere, is up while to mid- 20 and times bottom super-saturated waters in CH are supersaturated by up to 400 times. The from seabed deposits or hydrothermal vents (Hovland et al., 1993). An extensive re- 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 gC. CO f 12 , and the 10 2 × ¨ orth, M., An- C, were ob- corresponds ◦ 2 . The bottom wa- CO seems to occur. 2 f ¨ 3 O.: Non-conservative mol C or 6 , confirming earlier ob- 12 4 ¨ ork, G.: Variability in river 10 × 5 . ¨ om, I., and Semiletov, I. P.: Out- normalized to 15 , 2009. , 2010. tot ˚ ahlstr 1152 1151 . Assuming surface water at saturation in the 2 , which when integrated over 30 m depth results − , with extremely high values in the central western 1 2 − CO f doi:10.1029/2009GL040046 doi:10.1029/2010GB003834 , 2004. ¨ ¨ om, S., Kaltin, S., Jones, E. P., and Bj om, S., Hjalmarsson, S., W values were well above 1000 µatm and this, in combination with 2 This work was carried out by logistic support from the Knut and Alice from Siberian Shelf Seas by terrestrial organic matter decomposition, Geo- CO 2 f , giving an annual primary production of 0 2 distribution in the Eurasian Basin of the Arctic Ocean, J. Geophys. Res., 109, C01016, ff drogen ion concentration scaleRes., calibration Part of I, m-cresol 40, purple 2115–2129, and 1993. at-sea results, Deep-Sea seas during summer 1963, Arctic, 21, 67–83, 1968. water, alkalinity and silica in the Arctic Ocean, Deep-Sea.runo Res., 30, 87–94, 1983. doi:10.1029/2003JC001773 gassing of CO phys. Res. Lett., 36, L20601, Matter, edited by: Hansel, D. A. and Carlson, C. A., Academic Press, 665–683, 2002. derson, L. G., Sokolov, A., Humborg,behavior C., of Semiletov, I., dissolved and organic Gustafsson, carbongeochem. across Cy., the 24, Laptev GB4033, and East Siberian Seas, Global Bio- The decay of organic matter at the sediment surface that results in the high From the depth profiles of the carbon system parameters it was possible to infer a 500 000 km Codispoti, L. A. and Richards, F. A.: Micronutrient distributions in the East Siberian and Laptev Clayton, T. D. and Byrne, R. H.: Spectrophotometric seawater pH measurements: total hy- Anderson, L. G., Jutterstr Anderson, L. G., Jutterstr Anderson, L., Dyrssen, D., Jones, E. P., and Lowings, M. G.: Inputs and outputs of salt, fresh Anderson, L. G.: DOC in the Arctic Ocean, in: Biogeochemistry of Marine Dissolved Organic Cooperative Agreement NA17RJ1224; the US National(NS Science & Foundation (no. IS)); ARC-1023281 anda the (IPS), Russian no. Foundation 05-05-64213, forcontributed 08-05-00184 to Basic the (IIP)). Research implementation (no. We of 04-05-64819, are the 10-05-00996- project. also grateful to all our colleaguesReferences that Alling, V., Sanchez-Garcia, L., Porcelli, D., Pugach, S., Vonk, J., van Dongen, B., M Wallenberg Foundation and form Swedishcially Polar supported research by; Secretariat. the2010-4084); The Swedish the science Research European was Council Union finan- (contract projects,tract CarboOcean no. (contract no. 621-2006-3240 no. 211384) and 511176-2), and no. EPOCAAcademy 621- DAMOCLES (con- of (contract Sciences 018509); (FEBRAS); the the Far-Eastern Cooperative Branch Institute of for the Arctic Research Russian through NOAA Acknowledgements. levels also lowers pH.served making Values this below one of 7.5anthropogenic the ocean most units, acidification naturally pH acidified signalwater open will column marine in in environments. these a The shallow shortunder-saturated seas especially time of about with penetrate 50 respect all mcalcifying to bottom through organisms depth. aragonite. the are Calcium not Consequently carbonate favored the is andior conditions the of observations for total show alkalinity a and conservative thus behav- little formation or dissolution of CaCO to a DIC consumption ofin 35 a µmol kg consumption ofspring about when 1 production mol C m startsity. gives The an under-saturation estimate∼ was of observed a in corresponding about areal half productiv- of the ESS, estimated area of input of terrestrial organicthe matter, west, where as the deduced latter fromcay dominates the of in nutrient organic the distribution. matter surface Another couldobservations waters signature be showed to of methane, a microbial at high-spatial de- least variabilityservations of under of dissolved non-seawater a CH conditions. source from The methane. the seabed of possible both glacial and modernquantitative produced estimate of primary production. The under-saturation of opposite in the surface waters toters the are east, all i.e. high under-saturation in of nutrientsESS. CO and Here the high nutrient and lowganic oxygen matter. concentrations The shows origin extensive of microbial the decay organic of matter or- is both marine primary production and exceeding that of autotrophic in the west, resulting in over-saturation of CO 5 5 30 25 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , ¨ ´ O.: on, , 2002. ¨ a, L., and Gustafsson, olemann, J. A., Krumpen, ı ´ , 2008. ¨ oder, D.: Impact of the Arctic ¨ om, L.: Coulometric total carbon doi:10.1088/1748-9326/5/1/015006 ¨ andstr ´ anchez-Garc doi:10.1029/2001GC000302 1154 1153 ¨ ov, M., Hulth, S., and Olsson, K.: Rapid, high-precision doi:10.1029/2007JC004304 13C) of Arctic Amerasian continental shelf sediments, Int. 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V., Kirillov, S. Pipko, I. I., Semiletov, I. P., Pugach, S. P., W Pipko, I. I., Pugach, S. P., Dudarev, O. V., Charkin, A. N., and Semiletov, I. P.: Carbonate 5 5 25 30 20 15 30 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , (b) and sea ice coverage on 7 September 2008 1158 1157 (a) Map of the East Siberian Sea with illustration of the Siberian Costal Current following Map with station positions in the ESS Fig. 2. from University Bremen. the coast to thethe east ESS and and the themouth inflow inflow of of of the low water two salinity fromthe largest Laptev the New rivers, Sea Chukchi Siberian Indigirka Sea (LS) Islands and (CS) waterthe (NSI), Kolyma, to to Long the entering Strait the the Wrangel the (LSt). northeast northwest Island ESS of of (WI), are the the noted, ESS. Dmitry as The well Laptev Strait as (DLSt) and Fig. 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and bottom (c) and bottom water (a) 1160 1159 . Average SLP during the first half of August, second half of August and first half of The top panels show the salinity distribution in the surface water (d) while the lower panels show the temperature distribution in the surface water Fig. 4. September 2008, from NCEP data. water (b) Fig. 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | versus salinity, where the (b) 1162 1161 and total dissolved inorganic carbon (a) Total alkalinity Plot of temperature versus salinity. The freezing temperature as a function of salinity is latter is colored by the oxygen concentration. Fig. 6. illustrated by the dotted line. Fig. 5. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | color 2 CO f plot illustrate 2 , and CO 2 f CO f versus salinity. The color 2 CO f , and (c) , both color coded by (b) values, while the color in the 2 1164 1163 , silicate CO f (b) , nitrate . (a) (d) , nitrate (a) and by AOU (c) Plots of phosphate Depth profiles of phosphate Fig. 8. the oxygen concentration. Inillustrated the with latter the the horizontal atmospheric line at level 370–380 at µatm. the time of the investigation is coded by salinity symbols in the nutrient plots illustrate the Fig. 7. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in the in the (f) (c) 4 and CH (e) 2 CO f , (d) at the “alongshore” transect , nitrate (b) (c) 4 1166 1165 , phosphate (b) and dissolved CH , pH (a) (a) 2 CO f Distribution of Distribution of oxygen summer 2008. Fig. 10. Fig. 9. bottom waters of the ESS. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in the bottom waters (b) and aragonite (a) 1167 Distribution of the saturation state of calcite Fig. 11. of the ESS, expressed as omega. In both figures saturation is colored green.