Variability and Trends in Physical and Biogeochemical Parameters of the Mediterranean Sea during a Cruise with RV MARIA S. MERIAN in March 2018

Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 h ps://doi.o g/10.5194/essd-12-2747-2020 © Au ho (s) 2020. This wo k is dis ibu ed unde he C ea i e Commons A ibu ion 4.0 License. Physical and biogeochemical pa ame e s o he Medi e anean Sea du ing a c uise wi h RV Ma ia S. Me ian in Ma ch 2018 Dagma Hainbuche 1, Ma a Ál a ez4, Blanca As ay Uceda4, Gianca lo Bachi5, Vanessa Ca din3, Paolo Celen ano6, Spy os Chaikalis7, Ma ia del Ma Cha es Mon e o3,9, Giuseppe Ci i a ese3, Noelia M. Faja 4, F ancois F ipia 10, Lenna Ge ke2, Alexand a Gogou7, Elisa F. Gualla 4, Bi e Gülk1, Abed El Rahman Hassoun8, Nico Lange2, And ea Rochne 1, Chia a San inelli5, Tobias S einho 2, Tos e Tanhua2, Lidia U bini3, Dimi ios Velao as7, Fabian Wol 2, and And eas Welsch1 1Ins i u ü Mee eskunde, CEN, Uni e si ä Hambu g, Bundess aße 53, 20146 Hambu g, Ge many 2GEOMAR, Helmhol z-Zen um ü Ozean o schung Kiel, Wischho s . 1–3, 24148 Kiel, Ge many 3Dep . O Oceanog aphy, Is i u o Nazionale di Oceanog a ia e di Geo isica Spe imen ale – OGS, Bo go G o a Gigan e 42/c, 34010 Sgonico, T ies e, I aly 4Ins i u o Español de Oceanog a ía (IEO), Cen o de A Co uña, Spain 5Is i u o di Bio isica, CNR, Pisa, I aly 6Is i u o di Scienze Ma ine, Venezia, I aly 7Hellenic Cen e o Ma ine Resea ch, A hens, G eece 8Na ional Council o Scien i ic Resea ch in Lebanon, Na ional Cen e o Ma ine Sciences, Bei u , Lebanon 9Cen o Eu o-Medi e aneo sui Cambiamen i Clima ici CMCC, Bologna, I aly 10Max Planck Ins i u e o Chemis y, Mainz, Ge many Co espondence: Dagma Hainbuche (dagma .hainbuche @uni-hambu g.de) Recei ed: 2 Ap il 2020 – Discussion s a ed: 7 July 2020 Re ised: 17 Sep embe 2020 – Accep ed: 29 Sep embe 2020 – Published: 12 No embe 2020 Abs ac . The las ew decades ha e seen d ama ic changes in he hyd og aphy and biogeochemis y o he Medi e anean Sea. The complex ba hyme y and highly a iable spa ial and empo al scales o a mosphe ic o cing, con ec i e and en ila ion p ocesses con ibu e o gene a e complex and uns eady ci cula ion pa e ns and signi ican a iabili y in biogeochemical sys ems. Pa o he a iabili y o his sys em can be in luenced by an h opogenic con ibu ions. Consequen ly, i is necessa y o documen de ails and o unde s and ends in place o be e ela e he obse ed p ocesses and o possibly p edic he consequences o hese changes. In his con ex we epo da a om an oceanog aphic c uise in he Medi e anean Sea on he Ge man esea ch essel Ma ia S. Me ian (MSM72) in Ma ch 2018. The main objec i e o he c uise was o con ibu e o he unde s anding o long- e m changes and ends in physical and biogeochemical pa ame e s, such as he an h opogenic ca bon up ake and o u he assess he hyd og aphical si ua ion a e he majo clima ological shi s in he eas e n and wes e n pa o he basin, known as he Eas e n and Wes e n Medi e anean T an- sien s. Du ing he c uise, mul idisciplina y measu emen s we e conduc ed on a p edominan ly zonal sec ion h oughou he Medi e anean Sea, con ibu ing o he Med-SHIP and GO-SHIP long- e m epea c uise sec ion ha is conduc ed a egula in e als in he Medi e anean Sea o obse e changes and impac s on physi- cal and biogeochemical a iables. The da a can be accessed a h ps://doi.o g/10.1594/PANGAEA.905902 (Hainbuche e al., 2019), h ps://doi.o g/10.1594/PANGAEA.913512 (Hainbuche , 2020a) h ps://doi.o g/10.1594/PANGAEA.913608, (Hainbuche , 2020b) h ps://doi.o g/10.1594/PANGAEA.913505, (Hainbuche , 2020c) h ps://doi.o g/10.1594/PANGAEA.905887 (Tanhua e al., 2019) and h ps://doi.o g/10.25921/z7en-hn85 (Tanhua e al, 2020). Published by Cope nicus Publica ions. 2748 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 Da a co e age and pa ame e measu ed Reposi o y Re e ence. Table 1a and b and lis o a ailable da a se s (Table 1c). A link o he summa y page o he c uise MSM72 can be ound in he PANGAEA da abase unde h ps://www. pangaea.de/?q=msm72& .campaign%5B%5D=MSM72 (las access: 10 No embe 2020). Co e age. 34–41◦N, 6◦W–28◦E Loca ion name. The Medi e anean Sea Da e/Time s a . 2 Ma ch 2018 Da e/Time end. 3 Ap il 2018 1 In oduc ion Con a y o ea lie ideas ha he Medi e anean Sea is always in a s eady s a e, we now know in he ligh o new esea ch ha he Medi e anean Sea is no , and i is po en ially sensi- i e o clima ic changes (Malano e-Rizzoli, 2014). P o ing his a e he d as ic changes ha he eas e n Medi e anean (EMed) has unde gone in he pas . The la ges clima ic e en , named he Eas e n Medi e anean T ansien (EMT), occu ed in he EMed be ween he la e 1980s and ea ly 1990s, whe e deep-wa e o ma ion swi ched om he Ad ia ic Sea o he Aegean Sea. This episode modi ied he he mohaline cha - ac e is ics o he ou low h ough he Sicilian S ai , ad ec - ing anomalously sal y and wa m Le an ine In e media e Wa- e (LIW) o he wes e n Medi e anean Sea (WMed) and leading o a signi ican inc ease in empe a u e and sal in he in e media e and deep laye s o he WMed. Addi ion- ally, s ong deep con ec ion induced by ex eme a mosphe ic e en s du ing win e in 2004–2006 (low p ecipi a ion, cold, pe sis en winds) also enhanced sal and empe a u e in he en i e basin up o abou 1600m (Sch oede e al., 2006, 2008). This ab up clima e shi is e e ed o as Wes e n Medi e anean T ansien (WMT) and he physical changes a e compa able o he EMT, bo h in e ms o in ensi y and obse ed e ec s (Sch oede e al., 2008). The exis ence o bo h ansien s con adic s he hypo hesis o a s eady s a e. On he o he hand, i has also been p o en ha an EMT has ne e been obse ed be o e (Roe he e al., 2013). The cha ac e is ic o he Medi e anean Sea is also such ha i has he po en ial o seques e la ge amoun s o an h o- pogenic CO2, Can , since he Medi e anean Sea has high al- kalini y and empe a u e, which can be apidly anspo ed o deep by he o e u ning ci cula ion (e.g., Schneide e al., 2010). The column in en o ies o Can in he Medi e - anean a e among he highes ound in he wo ld oceans; he Medi e anean Sea hus s o es a signi ican po ion o he global an h opogenic emissions o Can despi e i s ela i ely small olume. Fu he mo e, ma ine dissol ed o ganic ca bon (DOC) ep esen s he la ges ese oi o educed ca bon (662× 1015 g C) on Ea h (Hansell, 2009), i he e o e plays a ma- jo ole in he global ca bon cycle. I s ole in he unc ion- ing o ma ine ecosys ems is equally c ucial since DOC is eleased a all he le els o he ood web as a byp oduc o many ophic in e ac ions and/o me abolic p ocesses and is he main sou ce o ene gy o he he e o ophic p oka y- o es (Ca lson and Hansell, 2015). Al hough mos o DOC is p oduced in si u, ex e nal sou ces (a mosphe e, i e s, sedi- men s) may a ec i s concen a ion and dis ibu ion. Physical p ocesses, such as deep-wa e o ma ion, he mohaline ci - cula ion, e ical s a i ica ion and mesoscale ac i i ies ha e been epo ed o be he main d i e s o DOC dis ibu ion in he Medi e anean Sea (San inelli, 2015; San inelli e al., 2015, 2013). The main scien i ic objec i e o he c uise epo ed he e was o add knowledge o he di e en scales and magni udes o a iabili y and ends in ci cula ion, hyd og aphy, and bio- geochemis y o he Medi e anean Sea. Key a iables we e measu ed in s a egic egions in o de o unde s and changes, he eason o occu ence, and he d i e s. In his con ex , his c uise is pa o he Med-SHIP and GO-SHIP long- e m e- pea c uise sec ion ha is conduc ed a egula in e als in he Medi e anean Sea o obse e changes and impac s on physical and biogeochemical a iables. The ollowing science ques ions a e add essed in his wo k. 1. Wha a e he long- e m changes and/o ends in physics and biochemis y in he Medi e anean Sea, including all he sub-basins? 2. How is he hyd og aphic si ua ion in he Medi e anean de eloping u he ollowing he EMT and WMT? Is he e s ill a endency o he sys em o e u n o he p e- EMT si ua ion and is he e a simila end in he WMed? 3. How a e eddies dis ibu ed in he EMed and WMed du - ing he c uise? Do hey di e in he sub-basins? To wha ex en is hea and sal ans e ed in o he e ical by ed- dies in he WMed and EMed du ing he c uise pe iod? 4. Wha is he up ake a e o he an h opogenic ca bon in he Medi e anean and is his changing o e ime? 5. Wha is he ex en o he a iabili y and ends in he in- en o y o biogeochemical a iables (including oxygen, nu ien s and dissol ed o ganic ca bon)? 6. Wha a e he baseline alues o a ely measu ed essen- ial ocean a iables (EOVs) such as dissol ed o ganic ca bon (DOC)? Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 h ps://doi.o g/10.5194/essd-12-2747-2020 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 2749 Table 1. (a) Lis o physical pa ame e s om Ma ia S. Me ian c uise MSM72 as seen in he PANGAEA da abase. The p ima y in es iga o was Dagma Hainbuche . (b) Lis o biogeochemical pa ame e s om Ma ia S. Me ian c uise MSM72 as seen in he CCHDO da abase. The p ima y in es iga o was Tos e Tanhua. (c) Lis o a ailable da a se s. (a) Pa ame e name Sho name Uni Me hod Commen s Da e/ ime Da e/ ime Geocode La i ude La i ude Geocode Longi ude Longi ude Geocode P essu e, wa e P ess dba CTD, SEA_BIRD SBE 911plus Tempe a u e, wa e Temp ◦C CTD, SEA_BIRD SBE 911plus Salini y Sal CTD, SEA_BIRD SBE 911plus Oxygen O2µmolkg−1CTD wi h a ached oxygen senso (SBE43) cal- ib a ed, co ec ed using Winkle i a ion P essu e, wa e P ess dba Unde way CTD (uCTD), Oceanscience Tempe a u e, wa e Temp ◦C Unde way CTD (uCTD), Oceanscience Salini y Sal Unde way CTD (uCTD), Oceanscience Dep h, wa e Dep h m Cu en eloci y eas –wes UC ms−1Shipboa d acous ic dopple cu en p o iling (SADCP) Cu en eloci y no h–sou h VC ms−1Shipboa d acous ic dopple cu en p o iling (SADCP) Dep h, wa e Dep h m Cu en eloci y eas –wes UC ms−1Lowe ed acous ic dopple cu en p o iling (lADCP) Cu en eloci y no h–sou h VC ms−1Lowe ed acous ic dopple cu en p o iling (lADCP) (b) Va iable Uni Dissol ed oxygen (O2) µmolkg−1 Sul u hexa luo id (SF6) molkg−1 CCl2F2(CFC-12) pmolkg−1 Ni a e (NO− 3) µmolkg−1 Ni i e (NO− 2) µmolkg−1 Phospha e (PO2− 4) µmolkg−1 Silica e (Si) µmolkg−1 Dissol ed ino ganic ca bon (DIC) µmolkg−1 To al alkalini y (TA) µmolkg−1 pH To al scale a 25 ◦C Ca bona e (CO2− 3) µmolkg−1 δ13C o DIC ‰ To al dissol ed ni ogen (TDN) µmolkg−1 To al dissol e phospho us (TDP) µmolkg−1 CHClF2(HCFC-22) pmolkg−1 C2H3Cl2F (HCFC-141b) pmolkg−1 C2H3ClF2(HCFC-142b) pmolkg−1 CH2FCF3(HFC-134a) pmolkg−1 C2HF5(HFC-125) pmolkg−1 CHF3(HFC-23) pmolkg−1 h ps://doi.o g/10.5194/essd-12-2747-2020 Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 2750 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 Table 1. Con inued. (c) Da abase Da a se h ps://doi.o g/10.1594/PANGAEA.905902 CTD (Hainbuche e al., 2019) h ps://doi.o g/10.1594/PANGAEA.913512 uCTD (Hainbuche , 2020a) h ps://doi.o g/10.1594/PANGAEA.913608 ADCP (Hainbuche , 2020b) h ps://doi.o g/10.1594/PANGAEA.913505 lADCP (Hainbuche , 2020c) h ps://doi.o g/10.1594/PANGAEA.905887 chemical da a (Tanhua e al., 2019) h ps://doi.o g/10.25921/z7en-hn85 pCO2(Tanhua e al., 2020) h ps://cchdo.ucsd.edu/c uise/06M220180 (addi ional) CTD and chemical da a 2 Da a p o enance The su ey was ca ied ou on he Ge man RV Ma ia S. Me ian om 2 Ma ch o 3 Ap il 2018. The c uise s a ed on He aklion, G eece, and ended in Cádiz, Spain. The main ocus o he c uise was on an eas –wes ansec ac oss he wes e n and eas e n Medi e anean Sea (Fig. 1) s a ing eas o C e e and ending nea he S ai o Gib al a , which is a epea ing hyd og aphic line in GO-SHIP (MED1). Di icul- ies wi h diploma ic au ho iza ions o Ma ine Scien i ic Re- sea ch (MSR) in he a ea eas o C e e made i impossible o us o ca y ou ou measu emen s as ini ially planned, and hus no da a we e ob ained eas o he Kasos S ai . Du ing he 33 d o he c uise we ca ied ou measu emen s o hyd og aphic and biogeochemical a iables along ack wi h he classical app oach, i.e., CTD, lADCP, uCTD in- s umen a ion and bo le samples on highly esol ed sec ions ac oss he Medi e anean Sea. The high esolu ion o CTD s a ions, enhanced o he physical pa ame e s by addi ional uCTD measu emen s, allowed us o esol e he eddy ield on he sec ions; he analysis was also suppo ed and comple- men ed by sa elli e da a. Mos sec ions and CTD-posi ions ollow p e ious sam- pling s a egies (c uise M84 and o he s along he GO-SHIP line MED-01, i.e., Tanhua e al., 2013) o allow long- e m end analyses. Along he di e en sec ions, CTD s a ions including sampling o chemical pa ame e s we e conduc ed app oxima ely e e y 30nm, CTD wi hou sampling abou e - e y 15–20 nm and wi h e en smalle spacing in he s ai s. In addi ion, unde way CTD measu emen s and ADCP measu e- men s we e pe o med be ween CTD s a ions. The wa e sampling p og am included measu emen s o all le el 1 a iables as de ined by GO-SHIP (i.e., oxy- gen, mac onu ien s, ansien ace s and he ca bona e sys em, h p://www.go-ship.o g/Da Req.h ml, las access: 10 No embe 2020) and measu emen s o he biogeochem- ical EOVs 13C, ni ous oxide (N2O) and dissol ed o ganic ca bon (DOC). These da a we e used o quan i y ends and a iabili y o en ila ion and biogeochemical cycles, in pa - icula up ake o an h opogenic ca bon. Sec ions we e addi ionally conduc ed h ough he impo - an passages o he O an o S ai , Kasos S ai , An iky he a S ai , Sicilian S ai and S ai o Gib al a , in o de o cha - ac e ize he incoming and ou going lows. CTD s a ions in he eas e n Ionian Sea we e ca ied ou o quan i y he low o he Le an ine Su ace Wa e (LSW) in o he Ad ia ic Sea and o ack he ou low o he Ad ia ic Deep Wa e (AdDW) in o he Ionian Sea. 3 Me hods 3.1 CTD ose e All oge he 136 CTD cas s we e pe o med, om which 18 we e ca alogued as iso opic (a ull sui e o obse a ions is gi en in Table 1a and b), 65 as chemical (i.e., GO-SHIP le el 1 a iables) and 59 as physical (i.e., only sampling o salini y). Due o he wa e amoun needed, wo cas s we e pe o med on mos o he iso opic s a ions, he i s cas was a ull p o ile and he second a shallow one. Du ing he phys- ical s a ions, wa e samples a h ee le els we e aken o salini y analysis. The samples we e hen analyzed on boa d using a Guildline Au osal Salinome e . A o al o 162 sam- ples in 59 s a ions we e aken du ing he c uise wi h an o se wi h espec o s anda d wa e a ying om 0.0002 o 0.0030 depending on he labo a o y empe a u e. The samples we e aken a dep h wi h a cons an salini y g adien o ensu e ha no na u al changes in salini y a ec he compa ison be ween sample and senso . The p ima y CTD sys em ( o speci ica ions, see Table 2) ini ially used on boa d was a Seabi d SBE9plus+CTD s/n 0285 om he Uni e si y o Hambu g connec ed o a SBE11 deck uni , con igu ed wi h a 24-posi ion SBE-32 pylon ( om GEOMAR) wi h 10 L Niskin bo les. The posi ion o bo le no. 23 and no. 24 was occupied by he lADCP ( o spec- i ica ions, see Table 3). Ini ially, he CTD was se up wi h wo senso s o empe a u e and conduc i i y, an oxygen sen- so , a luo ome e , and an al ime e . To es he con igu a ion and pe o mance o he ins umen a s a ion was ca ied ou on he C e an Sea a he s a o he c uise. Un o una ely, we had coun less p oblems wi h ins umen s, senso s, cables Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 h ps://doi.o g/10.5194/essd-12-2747-2020 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 2751 Figu e 1. S a ion map. Yellow do s a e CTD wi hou any chemical sampling, ed do s a e CTD wi h chemical sampling, cyan do s a e CTD wi h chemical and addi ional sampling o iso opes, yellow squa es a e he deploymen o d i e and loa s, blue lines a e ine esol ed uCTD and ADCP acks, and black lines a e acks wi h uCTD cas s be ween CTD s a ions. (a) De ail o he cen al map o he wes e n Medi e anean Sea. (b) De ail o he cen al map o he eas e n Medi e anean Sea. (c) De ail o he cen al map o he O an o S ai and no he n Ionian Sea. (d) De ail o he cen al map o he Ty henian Sea and Sicilian S ai . and he ose e du ing mos o he campaign ha o ced us o change hem e y o en wi h o he s a ailable on boa d, e- sul ing in a con inuous change o sys em con igu a ion. Thus, all di e en con igu a ions we e ca e ully conside ed when pos -p ocessing he CTD da a. Tempe a u e, salini y and p essu e da a we e pos - p ocessed by applying Seabi d so wa e and MATLAB® ou- ines. A his s age, spikes we e emo ed and 1dba a e ages calcula ed. A i s a emp o assess he pe o mance o he conduc i i y senso s ins alled on he CTD ose e was done by compa ing he salini y da a wi h he bo le samples ana- lyzed wi h he salinome e . The di e en ha dwa e se ups and con igu a ions a e aken ca e ully in o accoun du ing pos - p ocessing. O e all accu acies a e wi hin he expec ed ange o salini y (0.003). 3.2 Unde way CTD Unde way CTD measu emen s (uCTD; o speci ica ions, see Table 4) p o ide high- esolu ion p o iles o empe a u e, conduc i i y and dep h, which allow us o cha ac e ize he uppe -ocean p ope ies and iden i y he posi ion and cha ac- e is ics o mesoscale s uc u es. The ad an age o his ype o measu emen is ha i is no equi ed o s op he essel, h ps://doi.o g/10.5194/essd-12-2747-2020 Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 2752 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 Table 2. Used CTD ins umen and senso s. Owne o ins umen s a e ei he he Uni e si y o Hambu g, Ge many (I M-HH); he Na- ional Ins i u e o Oceanog aphy and Geophysics (OGS), I aly; o he p ope y o he essel Me ian (MSM). Ins umen /senso Se ial numbe Calib a ion (owne ) da e SBE 911plus/917plus CTD 285 (I M-HH) 3 Dec 2014 806 (MSM) 27 Jan 2016 807 (MSM) 8 Sep 2015 Tempe a u e 1: SBE-3-02/F 1717 (OGS) 22 No 2017 5716 (MSM) 15 Jul 2017 Conduc i i y 1: SBE-4-02/2 3442 (OGS) 22 No 2017 4152 (MSM) 14 Jul 2017 Tempe a u e 2: SBE-3-02/F 1294 (I M-HH) 11 Ap 2017 5719 (MSM) 15 Jul 2017 Conduc i i y 2: SBE-4-02/2 1106 (I M-HH) 12 Ap 2017 4156 (MSM) 14 Jul 2017 Oxygen 1: SBE 43 3392 (OGS) 19 Dec 2017 2417 (MSM) 16 Aug 2017 0951 (MSM) 1 Dec 2017 Oxygen 2: SBE 43 1761 (I M-HH) 11 Ap 2017 2418 (MSM) 15 Aug 2017 0881 (MSM) 23 Dec 2017 Fluo ome e WETLAB 1755 (MSM) 18 Ap 2017 1754 (MSM) 21 Dec 2017 SeaPoin (used on 1 s a ion) SCF2874 unknown SPAR 10 Ma 2016 PAR Chelsea 17 Oc 2016 i is only necessa y o main ain lowe eloci ies (abou 3kn) du ing he deploymen s o each g ea e dep hs. These mea- su emen s we e made wi h an Ocean Science uCTD sys em. The i s uCTD deploymen was done on 5 Ma ch, be- ween CTD 015 and 016 s a ions, and we con inued wi h his ype o sampling be ween each CTD s a ion o inc ease he sampling esolu ion. Un o una ely, se e al deploymen s we e canceled due o se e e wea he condi ions and no uCTD cas was pe o med when he dep h was shallowe han 500 m. All oge he , 176 cas s we e aken wi h dep hs ang- ing om 557 o 864 m. Two p obes we e used du ing he c uise wi h a no- ime- limi mode con igu a ion (apa om he i s cas con igu ed o s op eco ding a e 600 s, eaching 616 m dep h) in o de o ge longe eco ds. The p obe ail spools we e a ached o he winch h ough a ope loop ha was made new e e y day in he mo ning. Despi e he p obes being able o eco d se - e al cas s, da a we e downloaded igh a e each cas using a SBE so wa e in o de o a oid losing he da a in case he p obe was los and o ee up he memo y. The p obes we e exchanged when he ba e y was unning low (a ound 3.8 V). On h ee occasions no da a we e eco ded because he mag- ne was aken o wice be o e deploymen . Fo calib a ion pu poses, some addi ional cas s we e done igh a e he CTD cas in o de o compa e he da a se s. The p obes we e also sen down wi h he s a boa d CTD in s a ion 130. Da a iles we e p ocessed using a se o MATLAB® ou- ines. A e ex ac ing he downcas da a, he i s co ec ion was done o emo e inaccu acies in he descen a e, based on he wo k o Ullmann and Hebe (2014). Addi ionally, he da a we e aligned o he compa able CTD da a se s. 3.3 lADCP measu emen s Ocean cu en s we e s udied by means o e ical p o iles made wi h a lADCP-2 sys em (Wo kho se RD Ins umen s ype, Table 3) which included wo ADCPs ope a ing a a e- quency o 300kHz, one looking upwa d and he o he one looking downwa d. The sys em was placed in he ose e oc- cupying he posi ion o Niskin bo les 23 and 24. Du ing he c uise, he lADCP ba e ies we e changed wice: he i s ime on 17 Ma ch in S a ion 58 and he second ime on 27 Ma ch in S a ion 105. Excep o h ee s a ions (s a ion 73, 74, 80) wi h wa e dep hs less han 500m, lADCP measu emen s we e done a all CTDs. Fo hese s a ions, he cu en s we e obse ed by he ship-moun ed ADCP. A iso ope s a ions, lADCP p o iles we e only eco ded om he deep cas . The gained da a we e p ocessed wi h LDEO MATLAB®lADCP p ocessing sys em e sion 10.15 (Tu nhe , 2014). This so - wa e uses he aw lADCP da a, p ocessed CTD da a and na - iga ional da a om he CTD. The esul ing da a a e he u- and - eloci ies a he dep h. The bin size was se o 8 m. 3.4 Shipbo ne ADCP Du ing he whole campaign, unde way cu en measu e- men s we e aken wi h wo essel-moun ed Ocean Su - eyo s (ADCP) manu ac u ed by RDI. The i s , wi h a wo king equency o 75 kHz, co e ed app oxima ely he op 500–700 m o he wa e column. The numbe o bins was se o 100 wi h bin size o 8m. The second, wi h a wo king equency o 38 kHz, has a dep h ange o abou 1600 m, se wi h he same bin numbe as he p e ious one and bin size o 16 m. Bo h ins umen s un in na owband mode and we e con olled by compu e s using he con en- ional RDI VMDAS so wa e unde a Mic oso Windows sys em wi h a pinging se o as as possible. No in e - e ences wi h o he used acous ical ins umen s we e ob- se ed. The ADCP da a was pos -p ocessed a e wa ds wi h he CODAS3 So wa e Sys em (h ps://cu en s.soes .hawaii. edu/docs/adcp_doc/, las access: 10 No embe 2020), which allows ex ac ing da a, assigning coo dina es, and edi ing and co ec ing eloci y da a. Mo eo e , he da a we e co ec ed o e o s in he alue o sound eloci y in wa e , and mis- alignmen o he ins umen wi h espec o he axis o he Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 h ps://doi.o g/10.5194/essd-12-2747-2020 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 2753 Table 3. Used uCTD senso s. P obe 1 De ice ype Se ial numbe (owne ) 0289 90745 uCTD/SBE49 Fas Ca CTD 702-0289 (I M-HH) 0183 90745 uCTD/SBE 49 Fas Ca CTD 702-0183 (I M-HH) Table 4. Used lADCP. De ice Type Se ial numbe (owne ) WHM300 Mas e s/n no. 22762 (I M-HH) WHM300 Sla e s/n no. 22763 (I M-HH) ship (abou −2.8◦ o 75 kHz ADCP and abou −0.15◦ o 38 kHz ADCP). 3.5 Unde way CO2and O2measu emen s Unde way (UW) measu emen s o pa ial p essu e o CO2 (pCO2), and dissol ed oxygen pa ial p essu e (pCO2 he co esponding da a se in Table 1b only con ains pCO2) in seawa e we e ca ied ou by means o a Con os Hyd oC pCO2analyze o pCO2and an Aande aa op ode o oxy- gen. The ins umen s we e placed in a cooling box in he hanga . Seawa e was d awn om he ship’s cen i ugal pump o clean seawa e ha was con inuously lowing h ough he cooling box wi h he inle close o he ins u- men s. Wa e was pumped h ough a SeaBi d 5 salini y and empe a u e senso and on o he Hyd oC ins umen (Ge ke, 2020). The sys em ope a ed eliably h oughou he c uise, excep when da a acquisi ion was in e up ed o he pCO2ins u- men o 2 d di ec ly a e he ship’s cen i ugal pump was swi ched o . This led o a 5 d pe iod wi hou da a be ween 5 and 10 Ma ch. Du ing he c uise, 13 samples we e aken om he cooling box o disc e e measu emen s o pH and o al alkalini y. The UW measu emen s s a ed on 2 Ma ch a 20:20 and s opped on 1 Ap il 2018, a 14:00 UTC. The unde way oxygen measu emen s we e calib a ed by compa ing hem o he Winkle measu emen s aken o su - ace samples a he chemical CTD s a ions. 3.6 Dissol ed oxygen Dissol ed oxygen in seawa e was no only measu ed wi h he CTD, bu samples we e also aken a e e y s a ion and dep h along he c uise and epo ed in µmolkg−1. GO-SHIP guidelines ecommend Winkle measu emen s on all sam- ples, in addi ion o senso measu emen s on he CTD pack- age, and we la gely ollowed hose ecommenda ions. Un- o una ely, we had o ma k la ge numbe s o oxygen al- ues de e mined wi h he CTD as ques ionable due o he se - e al echnical p oblems wi h he CTDs and senso s. Usually, samples we e aken a s anda d dep hs, bu , especially a he su ace and a he bo om, he dep hs we e a ied acco d- ing o he equi emen s o he o he biogeochemical pa ame- e s. Oxygen was measu ed ollowing he au oma ic Winkle po en iome ic me hod, modi ied ollowing Langdon (2010). Ti a ions we e done wi hin he sampling calib a ed lasks using an Au oma ic Ti a o Me le Toledo T50 wi h a pla - inum combined elec ode. Reagen s o blank and hiosul a e s anda diza ion we e done daily by means o po assium ioda e s an- da d 1.667 mmol by OSIL, UK. Abou 1400 samples we e analyzed on boa d. The p ecision o dissol ed oxygen measu emen s was de e mined on i e eplica es a he beginning and a he end o he c uise (Table 5). In addi ion, du ing he c uise 46 duplica es we e analyzed. The esul s a e gi en in Table 6. 3.7 Nu ien s (ni i e, ni a e, phospha e and silica e), o al dissol ed ni ogen (TDN) and o al dissol ed phospho us (TDP) 3.7.1 Nu ien s Analyses we e pe o med a 40 ◦C on a ou -channel, Quaa o SEAL Analy ical Con inuous Flow Analyze s/n 8014549; h ps://www.seal-analy ical.com/P oduc s/ Segmen edFlowAnalyze s/QuAA o39Au oAnalyze / abid/ 814/language/en-US/De aul .aspx (las access: 10 No em- be 2020), acco ding o Hansen and Ko ole (1999). Ni i e was de e mined h ough he o ma ion o a eddish- pu ple azo dye and measu ed a 520nm (SEAL Me hod no. Q-030-04 Re . 2). Ni a e was educed o ni i e in a coppe ized cadmium educ ion coil and hen de e mined as desc ibed o ni i e (SEAL Me hod no. Q-035-04 Re . 4). The de e mina ion o phospha e was based on he educed blue phospho-molybdenum complex and hen measu ed a 880 nm (SEAL Me hod no. Q-031-04 Re . 1). Silica e was de e mined by means o acidic educ ion o silicomolybda e o molybdenum blue and hen measu ed a 820nm (SEAL Me hod no. Q-038-04 Re . 0). Abou 1400 nu ien samples we e analyzed on boa d. The onboa d p ecision o nu ien measu emen s was de e mined on i e eplica es a he beginning and a he end o he c uise. The esul s a e shown in Table 7. In addi ion, du ing he c uise 140 duplica es we e ana- lyzed. The esul s a e shown in Table 8. h ps://doi.o g/10.5194/essd-12-2747-2020 Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 2754 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 Table 5. P ecision o dissol ed oxygen (SD is s anda d de ia ion, and CV is coe icien o a ia ion). Pa ame e Beginning o he c uise End o he c uise Mean µM SD µM CV% Mean µM STD µM CV% Dissol ed oxygen 196.07 0.13 0.07 198.84 0.14 0.07 Table 6. Resul s o duplica es. Pa ame e Range Mean absolu e Mean Rela i e (µM) di e encea(µM) pe cen age di e enceb Dissol ed oxygen 179–240 0.18 0.09 aAD = | duplica e no. 1 −duplica e no. 2|.bRPD % =absolu e di e ence ·100 /mean (dupl. no. 1, no. 2). An in e nal quali y check was daily pe o med by means o analyses o QUASIMEME samples, which p o ided e- sul s wi hin he al eady ce i ied anges. 3.7.2 TDN and TDP Abou 550 samples o o al dissol ed ni ogen and o al dis- sol ed phospho us (TDN and TDP) on land-based labo a o y analyses we e collec ed and ozen a −20 ◦C a e il a ion on p e-combus ed GF/F il e . The dissol ed o ganic compo- nen s, dissol ed o ganic ni ogen (DON) and dissol ed o - ganic phospho us (DOP) we e subsequen ly calcula ed by sub ac ing hei mine al cons i uen s (NO3+NO2) and PO4, espec i ely. 3.8 Disc e e CO2sys em measu emen s Disc e e CO2 a iables we e measu ed on boa d, i.e., dis- sol ed ino ganic ca bon (DIC), pH, o al alkalini y (TA) and ca bona e ion (CO2− 3); hese a iables we e measu ed a se- lec ed s a ions and dep hs (Table 9). In addi ion, disc e e samples o DIC, pH and TA we e analyzed speci ically om su ace Niskin bo les o be compa ed wi h he con inuous wa e supply eeding he pCO2sys em in de e mined s a- ions. Fo u he de ails, especially abou he on-boa d p o- cedu e o he measu emen o samples, see Hainbuche e al. (2018). 3.8.1 DIC Samples o DIC we e collec ed ollowing ansien ace s and dissol ed oxygen in 500mL bo osilica e bo les ollow- ing s anda d p ocedu e. No poison was added. Samples we e le a oom empe a u e in he da k un il analysis a maximum o 48 h a e collec ion. DIC samples we e analyzed wi h a MARIANDA VINDTA 3D sys em coupled wi h a UIC 5011 coulome e . This analysis o e all consis s o ex ac ing sea- wa e CO2 om a known olume o sample by adding phos- pho ic acid, ollowed by coulome ic de ec ion (Johnson e al., 1993). No calib a ion uni was a ailable o he sys em. A new coulome ic cell was p epa ed o e e y ba ch o anal- ysis and he accu acy o he DIC measu emen s was assessed by using Ce i ied Re e ence Ma e ial (CRM no. 158 and no. 170, p o ided by And ew G. Dickson, UCSD). The cali- b a ion ac o ob ained om he CRM was used o adjus ing he inal DIC o each sample measu ed in he co esponding ba ch o analysis. In addi ion, subs anda d seawa e (s abi- lized seawa e om he C e an Sea 700 m salini y minimum, s o ed in he da k in a 30L con aine ) was analyzed a he be- ginning and end o he ba ch analysis as a seconda y quali y con ol. The p ecision o he DIC measu emen s was checked by (1) double analysis om he same sample and (2) eplica e analysis om ou o i e samples collec ed om he same Niskin bo le. The p ecision is es ima ed o be 1 µmolkg−1, and he accu acy is assumed o be 2µmolkg−1. 3.8.2 pH Seawa e spec opho ome ic pH was measu ed ollowing Clay on and By ne (1993) a almos all dep hs in he chemi- cal and iso ope s a ions du ing he MSM72 c uise (Table 1). This me hod consis s on adding a olume o indica o solu- ion o he seawa e sample, so ha measu ing he abso bance o he sample a di e en wa eleng hs and ob aining he a- io be ween wo o he wa eleng h’s abso bance is p opo - ional o he sample pH. The indica o was a 2mM solu- ion o unpu i ied m-c esol pu ple (Sigma Ald ich®) p e- pa ed in seawa e and main ained in he da k wi h no ai con ac (abso bance a io o 1.30). Samples we e aken ol- lowing s anda d p ocedu es immedia ely a e DIC and di- ec ly in o cylind ical 10cm pa h leng h op ical glass cells. The cells we e he mos a ized a 25±0.2◦C o 1 h be- o e analysis. Abso bance measu emen s we e ob ained in he he mos a ed chambe o a double-beam UV 2600 Shi- madzu spec opho ome e . The equipmen was checked be- o e he c uise o he abso bance and wa eleng h accu acy using holmium s anda ds. The pH alues on he o al scale Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 h ps://doi.o g/10.5194/essd-12-2747-2020 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 2755 Table 7. On-boa d p ecision o nu ien measu emen s. Pa ame e Beginning o he c uise End o he c uise Mean µM STD µM CV% Mean µM STD µM CV % Ni i e (1) 0.01 0.01 100 0.03 0.01 56.5 Ni i e +ni a e 4.94 0.01 0.2 9.01 0.02 0.2 Phospha e 0.18 0.01 5.5 0.41 0.01 3.1 Silica e 8.34 0.03 0.3 9.55 0.04 0.5 Table 8. Analysis o duplica es. Pa ame e Range Mean absolu e Mean ela i e (µM) Di e encea(µM) pe cen age di e enceb Ni i ec0–0.19 0.01 48.77 Ni i e +ni a e 0.33–9.86 0.02 0.42 Phospha e 0–0.47 0.01 5.13 Silica e 0.93–11.00 0.04 0.72 aAD = | duplica e no. 1 −duplica e no. 2|;bRPD % =absolu e di e ence ·100 /mean (dupl. no. 1, no. 2). cNi i e s a is ics was gi en jus o comple eness, since he concen a ion le els eco ded we e oo low and o en below he de ec ion limi . Table 9. To al numbe o CO2sys em samples analyzed du ing he MSM72 c uise. The o al numbe o i ed bo les was 1723. DIC pH TA CO2− 3Su ace Samples 479 1160 949 391 22 we e calcula ed and e e ed a 25◦C by using he o mula by Clay on and By ne (1993). The injec ion o he indica- o in he sample sligh ly changes he sample pH. Follow- ing s anda d ope a ing p ocedu es, double addi ions o he indica o we e pe o med o e a pH g adien in o de o ob- ain he co esponding co ec ion (Hainbuche e al., 2018). The pH accu acy was con olled measu ing TRIS bu e solu- ion samples (ba ch no. 72, p o ided by And ew G. Dickson, UCSD). TRIS samples we e s abilized a h ee di e en em- pe a u es co e ing he pH ange ound du ing he MSM72 c uise. Di e ences be ween measu ed and heo e ical TRIS pH a ied be ween 0.009 o 0.005. The pH p ecision was checked by eplica e analysis om cells collec ed a he same Niskin om su ace and deep wa e s. The p ecision is es- ima ed o be 0.0004 pH uni s, and he accu acy was es i- ma ed o be 0.005 pH uni s. Du ing he c uise, some samples we e also analyzed wi h pu i ied m-c esol pu ple p o ided by Robe H. By ne (USC). 3.8.3 TA TA was analyzed ollowing a double end poin po en iome - ic echnique by Pé ez and F aga (1987) u he imp o ed by Pé ez e al. (2000). This echnique is as e han he whole cu e i a ion, wi h compa able esul s (Min op e al., 2000). TA was measu ed a mos s a ions and dep hs (Table 1). Seawa e samples o TA we e collec ed a e pH samples in 600 mL bo osilica e bo les ollowing s an- da d p ocedu es. Samples we e le a oom empe a u e in he da k un il analysis a a maximum o 48h a e collec- ion. TA was measu ed by i a ion wi h 0.1 N hyd ochlo- ic acid dispensed wi h an au oma ic po en iome ic i a o , Ti ando Me ohm®, p o ided wi h a combina ion glass elec- ode coupled wi h a empe a u e p obe. The elec ode was s anda dized using a 4.41 pH a ala e bu e made in CO2- ee seawa e . The TA accu acy was assessed wi h CO2CRM (ba ch no. 170, p o ided by And ew G. Dickson, UCSD) In addi ion o he CRM calib a ion, a d i con ol was con- duc ed by analyzing subs anda d seawa e (big olume o seawa e s o ed in he da k, as o DIC) a he beginning and a he end o he analysis session. Each sample was measu ed wice and he mean alue is epo ed, wi h he mean s anda d de ia ion o all duplica e di e ences being 0.6 µmolkg−1. In addi ion, ypical ep oducibili y analysis we e pe o med om samples collec ed om he same Niskin bo le a di e - en s a ions along he c uise. The TA p ecision is es ima ed o be 1 µmolkg−1and he accu acy 2µmolkg−1. 3.8.4 CO2− 3 The CO2− 3ion concen a ion was de e mined spec opho o- me ically ollowing By ne and Yao (2008) inco po a ing he ecen imp o emen s by Pa sa as e al. (2015), a selec ed s a ions and dep hs (Table 1). Samples o CO2− 3we e col- lec ed a e TA ollowing he same p ocedu e as o pH bu wi hin cylind ical op ical qua z 10cm pa h leng h cu e es. The cells we e s abilized a 25◦C o 1 h be o e he analysis h ps://doi.o g/10.5194/essd-12-2747-2020 Ea h Sys . Sci. Da a, 12, 2747–2763, 2020 2762 D. Hainbuche e al.: Physical and biogeochemical pa ame e s o he Medi e anean Sea in Ma ch 2018 Hainbuche , D., Ca din, V., Velao as, D., and Mon e o, M. F.: Phys- ical oceanog aphy du ing MARIA S. MERIAN c uise MSM72, PANGAEA, h ps://doi.o g/10.1594/PANGAEA.905902, 2019. Hansell, D. 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