NABOS 2013 Arctic Expedition aboard RV “Akademik Fedorov”

August 21 – September 22, 2013

Expedition Organizers: International Arctic Research Center, University of Alaska Fairbanks, USA Arctic and Antarctic Research Institute, St.Petersburg, Russia

Summer School Organizers: International Arctic Research Center, University of Alaska Fairbanks, USA A.M. Obukhov Institute of Atmospheric Physics RAS, Moscow, Russia

Expedition is funded/supported by:

National Science Foundation of the USA

Japan Agency for Marine Science and Technology

Russian Federal Service for Hydrometeorology and Environment Protection

Summer school is funded/supported by:

National Science Foundation of the USA

Russian Academy of Sciences

Russian Foundation for Basic Research

Content

Page 1. Introduction (V. Ivanov) ……………………………… 4 2. Cruise itinerary (V. Ivanov) ……………………………… 4 3. Meteorological and ice conditions (I. Repina, A. Masanov, ……………………………… 6 V. Ivanov) 4. Description of observations ……………………………… 8 4.1 Moorings deployment (I. Wadington, R. Rember, V. ……………………………… 9 Ivanov) 4.2 Other devices deployment (J. Kemp, R. Rember, ……………………………… 11 V.Ivanov) 4.3 Hydrographic (CTD/LADCP/XCTD/XBT) measurements ……………………………… 13 (S. Kirillov, V. Ivanov) 4.4 Hydrochemical sampling and measurements ……………………………… 14 4.4.1 Sampling Rationale and Proposed Work for ……………………………… 14 Hydrochemical Observations (R. Rember) 4.4.2. Dissolved oxygen, nitrate, barium and stable oxygen ……………………………… 15 isotopes (M. Alkire, R. Rember) 4.4.3. Nutrients and Dissolved Inorganic Carbon (T. ……………………………… 18 Whitledge, J. Mathis, P. Rivera) 4.4.4. Chlorophyll and Fluorescence Measurements (D. ……………………………… 19 Stockwell) 4.4.5. Carbon and nitrogen productions of phytoplankton (J. ……………………………… 19 H. Lee, H.W. Lee) 4.4.6. NO3- N and O isotopes (J. Granger, L. Treibergs) ……………………………… 21 4.4.7. Silicate and methane measurements (E.Vinogradova, A. ……………………………… 21 Nikulina) 4.4.8. Water sampling for DOC/POC, n-alkanes and mass ……………………………… 25 concentrations of particulate matter (A. Drozdova, M. Ponyaev) 4.4.9. Water sampling for carbon, nitrogen and phosphorus ……………………………… 26 (K. Artamonova, I.Gangnus) 4.5. Air-sea interaction (I. Repina, L. Yurganov, K. Komatsu) ……………………………… 27 5. Summer School aboard “Akademik Fedorov” (V. Alexeev, ……………………………… 35 I. Rrpina) 6. Summary (V. Ivanov) ……………………………… 37

1. Introduction

The 2013 research cruise in the Arctic Ocean aboard icebreaker Akademik Fedorov was the 9th annual expedition under the aegis of NABOS (=Nansen Amundsen Basin Observations System) conducted by International Arctic Research Center (IARC) University of Alaska Fairbanks, USA in partnership with Arctic and Antarctic Research Institute (AARI) St.Petersburg Russia. The main goal of the NABOS project is to provide quantitative assessment of circulation and water mass transformation along the principal pathways transporting water from the Nordic Seas to the Arctic Basin. Specific feature of this cruise was that it took place under conditions of substantially reduced summer ice cover over the major part of the Arctic Ocean. Reduced sea ice causes changes in the water column and in the overlying atmosphere. Documenting of these changes was the main target of the NABOS 2013 cruise. The scope of this goal and the opportunities of extended scientific research in the Arctic, provided during NABOS expeditions, encouraged scientific institutions from the USA, Europe and Asia to raise funds, contribute to the cruise program and to send their personnel to the expedition, thus giving it a true multidisciplinary status. The information collected during the cruise is unique and very valid for understanding of the Arctic climate change. Important outreach component of the cruise was the Summer School, which provided an excellent opportunity for graduate students, PhD students and early career scientists from US, Europe and Russia to learn about the climate change in the Arctic and to participate in field experiments onboard. This report informs about the cruise route, schedule, meteorological and ice conditions and briefly describes observations, carried out during the 2013 NABOS cruise and Summer School activities.

2. Cruise itinerary

Icebreaker Akademik Fedorov left Kirkenes, Norway at 8 a.m. local time on August 21, 2013 after loading/mounting the equipment and embarkation of the expedition team. The research area included Eurasian continental margin from St. Anna Trough to the East Siberian Sea (Fig. 1). Operation area partly overlapped with the Russian Exclusive Economic Zone (EEZ). On August 23, 2013 the vessel arrived at the first CTD station at the eastern flank of St. Anna Trough. The glider (underwater autonomous vehicle) was launched and test CTD cast was carried out. During the next two days the ship was steaming towards the main mooring line in the Laptev Sea. The route was planned along the pack ice edge without entering the consolidated pack in order to save time. Five CTD casts were fulfilled en route about 80 miles apart. On August 26 in the morning the first mooring was deployed on the Laptev Sea shelf. The second mooring was deployed on the same day in the evening. No ice was present at both mooring sites. During the next 2.5 days the CTD line along 126ºE was accomplished and two more moorings were deployed at the northern end of this line. These two deployments were carried out in the ice covered area with total ice concentration 60-80%. On August, 29 the ship turned to the east and started steaming to the northern end of the second mooring line. Three CTD casts were done within the next 2 days before the ship entered consolidated heavy ice pack. The speed dropped to 2-3 knots and the ship had to move back and force in order to make its route. On August 30 it was decided to get out of the ice massif using the shortest way and to steam towards the southern end of the second mooring line along the ice edge in the open water. CTD casts at the second mooring line started on August 31 early in the morning. The mooring at this line was deployed on the same day in the evening. On September, 1 the ship reached the ice edge in the south and started steaming towards the easternmost mooring line, doing CTD casts en route. At about 153 ºE the ship was stuck in the heavy consolidated pack ice with the thickness up to 2 m. Compression of ice additionally impeded further motion. The easternmost mooring line appeared to be in the area with heavy ice conditions, the ship could not operate successfully. Basing on this information the decision was taken to cancel recovery and redeployment of the easternmost mooring and to update the operational cruise plan accordingly.

Fig.1 NABOS 2013 cruise map

On September, 4 the ship turned back towards the southern end of the second mooring line at 144ºE and started the CTD line towards the south end of the first mooring line, thus enclosing the CTD polygon, containing cross-slope sections at 126 and 142ºE. This section was accomplished on September, 6 early in the morning. The same day two remaining moorings scheduled for the first mooring line, were deployed. During triangulation of the M14 mooring it appeared that the upper flotation did not submerge, pointing out that the bottom depth in the deployment point was less than it was supposed to be. On the next day M14 mooring was recovered and redeployed at the correct depth. On September, 8 the ship got out of the ice massif and started the first additional CTD section, crossing the Laptev Sea slope at 110ºE. Late in the evening on September, 10 this CTD line was interrupted at the middle slope by stormy conditions: strong wind (over 18 m/s) and high waves (over 3 m), which made the rosetta launch unsafe. The decision was taken to shut down further sampling at this section. The ship sheltered in the marginal ice zone at the northern end of the second additional section (105ºE). This section was finalized at Severnaya Zemlya shelf on September, 13. The same day the third additional cross-slope transect was done at 95ºE with the starting point at the traverse of cape Arkticheskiy. The mooring, which remained due to not getting to the easternmost mooring line, was deployed at 2700 depth at this mooring line on September 14. The same day the ship turned towards the northernmost scheduled point at 90ºE, 85ºN. Due to presence of heavy pack ice at this point, the CTD line was started at 84º30‟N. Stormy conditions interrupted this line in the evening of September, 16 when the ship was close to the last mooring deployment point. On September, 17 in the morning the state of the sea reasonably calmed down and the deployment of the mooring was done. The same day in the evening the section along 90ºE was resumed. Stormy conditions prevented rosetta launch at the upper slope points. The ship continued slowly moving towards the shelf and remaining sampling points were casted with expendable devices (XCTD and XBT). On September, 18 the ship moved to the position of the final CTD section across St. Anna Trough. This section was accomplished by the morning of September, 19. At noon of September, 19 the ship started steaming towards Kirkrenes, where she safely arrived at 18:00 on September 22.

3. Meteorological and ice conditions

Weather conditions during the cruise were rather variable. The air temperature was about zero degrees on the average (Fig. 2). However, in the eastern part of operational area the temperature was about -5-7ºC. The surface water temperature was well above freezing point in the open water and near the freezing point under the ice. High humidity in the MIZ caused fast icing of meteorological instruments, thus biasing the measurements of sea-air interaction.

10 T air mean 8 Tair max 6 Tair min

4

2

C 0 0

-2

-4

-6

-8 235 237 239 241 243 245 247 249 251 253 255 257 259 261 263 Julian day Fig. 2. Surface air temperature during the cruise

Extended areas of open water led to development of high waves under the influence of strong winds. During the cruise there were several episodes when strong wind (up to 20 m/s) was observed when the ship was operating in the open water. In two instances high waves interrupted rozetta sampling at cross-slope transects. 25 mean wind max wind 20

15 W, m/s 10

5

0 236 238 240 242 244 246 248 250 252 254 256 258 260 262 Julian day

Fig. 3. Wind speed during the cruise

Ice conditions during the cruise were characterized by the existence of well pronounced marginal ice zone (MIZ), which separated zones of consolidated pack ice with 100% concentration and open water areas (see Fig. 4).

Fig.4 SSM/I ice map on September, 9, 2013

(a) (b)

(c) (d)

Fig.5. Ice conditions along the ship route: August, 24-25 (a); August, 26-29 (b); August, 30 – September, 3 (c); September, 15-16.

Depending on the area (see Fig.5), transects and mooring operations were carried out either in the ice free waters, or in the pack ice. Ice thickness was on the average 40-100 cm; it was predominantly first- year ice, substantially rotten and melted from below. The thickest ice was encountered at the easternmost area reached by the vessel – to the east of 150ºE. Heavy consolidated ice in this area prevented the ship from moving further to the east. General statement, which comes out of this year experience with mooring deployment operations in the ice covered area is that under the conditions of 80-100% consolidated pack, mooring deployments from R/V “Akademik Fedorov” are hardly probable, because of limited ability of ship maneuvering in ice covered seas. It is expected (although not checked in this cruise) that the restriction on ice concentration during moorings recovery for this ship is even less: about 50-60% - to substantially complicate mooring recovery and 80-100% - to make mooring recovery practically impossible.

4. Description of observations

Observations/measurements during the 2013 NABOS cruise included routine operations of moorings deployment, ITPs deployment and CTD transects along the mooring lines plus additional field activities by NABOS partners. Specific operation, which was carried out during the cruise, was the glider launch. All scientific teams, except mooring tech team, operated in watches, 12 hours each.

4.1 Moorings deployment

Nine mooring deployments were successfully accomplished during the cruise. Three moorings (M15, M16 and M3) were deployed in the ice covered areas with ice concentration up to 60-80% and ice thickness 40-100 cm. Other moorings were deployed in the ice free waters. All mooring deployments were done using the “anchor-first” procedure. Time expenses on deployment operations were between 4 and 8 hours (depending on complexity of mooring configuration), including triangulation, which normally took about 1.5-2 hours. During the deployment the ship was either drifting (in ice free water), or moving slowly forward (at a speed about 1.5-2 knots) in order to keep the position within the lead and to keep the mooring line off the stern. Before mooring release the ship went to the position of target depth (monitored by echosounder), where the drop was performed. During triangulation of the M14 mooring it appeared that the upper flotation did not submerge, pointing out that the bottom depth in the deployment point was less than it was supposed to be. The reason why this had happened is not perfectly clear. The most probable explanation is malfunctioning of the echosounder, which takes place when thrusters are in operation. The latter is needed for ship to keep her position at high seas, which was the case during M14 deployment. On the next day M14 mooring was recovered and redeployed at the correct depth. Although unexpected, the recovery of M14 provided a drill for future recoveries. It went quite successful. Zodiac boat may not be used during that recovery because of high seas. Therefore operation of floating mooring catching was carried out from the work deck. After being fixed, the mooring line was moved by hands along the board to the stern and connected to the other line mounted on the Lebus winch through the A-frame. Recovery operation took about 4.5 hours. NABOS moorings inventory, as it is on the end of September 2013 cruise is presented in Table 1. Location of moorings at 126ºE line is presented on Fig. 6.

Table 1 Moorings inventory M00RING Date DEPLOY Lat./Long. Depth Instruments M1-1 26th August 2013 Deployment 77 04.25247 N 250m 3 x SBE37 125 48.2878 E 1 x ADCP 75kHz M1-2 26th August 2013 Deployment 77 10.3761 N 787m 1 x SBE37 125 47.5155 E 1 x ADCP 300khz 1 x MMP 1 x ADCP 75kHz M1-3 6th September 2013 Deployment 77 39.286 N 1849m 1 x SBE37 125 48.4014 E 1 x ADCP 300khz 1 x MMP 1 x ADCP 75kHz M1-4 8th September 2013 Deployment 78 27.5431 N 2721m 4 SBE37 125 53.7583 E 1 x ULS 1 x ISUS 1 x ODO/SBE37 1 x ADCP 300khz 1 x BPR 1 x ADCP 75kHz M1-5 28th August 2013 Deployment 80 00.1986 N 3443m 1 x ADCP 300khz 125 59.6729E 4x SBE37 1xMMP 15 x SBE56 M1-6 29th August 2013 Deployment 81 08.18237 N 3900m 1 x ADCP 300khz 125 42.6732 E 4x SBE37 1xMMP 1 x ADCP 75kHz 15 x SBE56 M3 31st August 2013 Deployment 79 56.1358 N 1335m 1 x ADCP 300khz 142 14.8871 E 8x SBE37 15 x SBE56 1 x ADCP 75kHz M5 17th September 2013 Deployment 82 30.9012 N 2503m 5 x SBE37 89 59.5992 E 1 x ADCP 300khz 1x ADCP 75khz 1 x ISUS I X ODO/SBE37 15 x SBE56 "M9" 14th September 2013 Deployment 82 05.9846 N 2710m 4 x SBE37 97 01.8517 E 1 x ADCP 300khz 1 x ADCP 75kHz 1 x ODO/SBE37 1 x ISUS 1 x BPR 1 x ULS

Fig.6. Location and configuration of moorings along 126ºE

4.2 Other devices deployment

Several other devices were deployed during the NABOS-2103 cruise. They are listed in the following tables. Location of ITP deployments is presented in Table 2. Position of all ITP buoys in the Arctic Ocean as on September 17, 2013 is shown in Fig. 6.

Table 2 Deployed ITP-buoys Time # Date Latitude, deg. N Longitude, deg. E. GMT 72 30.08 0.00 80° 49.505‟ 132° 37.966‟ 59 3.09 13.00 80° 15.700‟ 155° 54.000‟ 74 7.09 16.00 80° 23.182‟ 126° 23.643‟ 75 11.09 10.38 82° 03.637‟ 111° 57.731‟ 73 15.09 12.45 84° 26.310‟ 93° 30.345‟

Fig.6. ITP locations on September, 17, 2013

All ITP buoys were deployed on ice with thickness more than 120 cm. John Kemp, who was responsible for ITP deployments specially acknowledged the excellent work that the head of the ice team Andrei Masanov did in support of the Ice Tethered Profiler (ITP) project this year on the NABOS cruise. This field program involved deploying five ITP moorings suspended from ice floes along the cruise track. Mr. Masanov was tasked with finding suitable multiyear floes that could support a profiler for several consecutive years. With his wealth of knowledge of sea ice, he was able to find a floe at every site that exceeded general expectations. Meteorological buoys were deployed along the ship track in the ice free water or on ice. Deployment in the ice free waters were done by dropping the device overboard at a speed about 2 knots (normally this was done during ship acceleration after CTD station). Deployments on ice were done together with corresponding ITP deployments. Info on these deployments is presented in Table 3 and on Fig. 7.

Table 3 Deployed meteorological buoys Buoy Latitude Longitude Type Owner # Deg. N Deg. E 1 77.1 125.5 No Drogue Blouche 2 78.9 125.8 Drougue Rigor 3 81.2 125.6 No Drogue Blouche 4 80.8 132.6 Drougue Rigor 5 79.9 142.3 No Drogue Blouche 6 79.7 146.4 Drougue Rigor 7 80.2 155.7 60 m Steele Thermistor 8 79.3 142.8 No Drogue Blouche 9 78.5 134.3 No Drogue Blouche 10 77.9 127.9 60 m Steele Thermistor 11 77.7 125.8 Drougue Rigor 12 77.8 125.8 No Drogue Blouche 13 80.4 126.4 60 m Steele Thermistor 14 79 122.5 No Drogue Blouche 15 78.9 116.2 Drougue Rigor 16 80.1 109.3 No Drogue Blouche 17 81.26 107.25 No Drogue Blouche 18 81.9 96.5 Drougue Rigor 19 84.7 90 Drougue Rigor 20 82.1 90 Drougue Rigor

Fig.7. Meteorological buoys deployment locations

Two other types of buoys were deployed on ice together with ITP-59: Ice Mass Balance (IMB) buoy and O-buoy were deployed at the same ice field with the size 2-3 km (first year ice with thickness about 140 cm and snow thickness about 5 cm). Geographical coordinates of these deployments are: 80° 15,7‟ N, 155º 54„ E. Glider launch (see Fig. 8) had occurred before the test station at the position 80.98ºN, 72.92ºN. The launch and post-launch testing took about one hour. During the next 10 days the glider was online, transferring the data to the receiving center in California. After this time the communication with glider was lost, which indicated that the device has been gone. Possible reasons are unknown, but the most likely is some technical problem.

Fig.8, Glider launch on September, 23, 2013.

4.3 Hydrographic (CTD/LADCP/XCTD/XBT) measurements

116 CTD/LADCP casts and 49 XCTD/XBT drops were carried out during the cruise. These stations were taken at 7 cross-slope transects and 3 along-track ones as shown in Fig. 1. In the deep basin (> 1500 m) one out of 3 casts was done to the bottom. Two casts in between were done to 1000 m. At the test station all equipment (including ship borne CTD winch, rosetta, etc.) was tested and proved its satisfactorily operational readiness. However, during operations several problems were encountered with the winch. At one of stations the device evenly redistributing the cable along the drum was broken (probably because of aging) and was replaced by the other one. At the other station the internal chain in the winch was broken and replaced by the other one. Although these incidents did not seriously affect the total cruise timing, in future cruises (if using the same ship) routine maintenance of the CTD winch should be recommended. More practical is to replace this winch by the newer one. Once, during high seas the cable wire of the winch experienced extra tension and had to be resealed. The casts were taken to the depth 30 m above the seabed, which was monitored by the rosetta- mounted altimeter. This offset depth was highly recommended by the person, responsible for CTD sensors – Rob Rember, who motivated the lack of sampling in the bottom boundary layer by the threat to oxygen sensor, which could emerge due to possibility of high concentration of suspended particles near the bottom. Dissolved oxygen and temperature sections, taken during the cruise are presented in Fig. 9. General conclusion coming out of these plots confirms the earlier proposed concept (e.g. Ivanov and Aksenov, 2013) about rapid transformation of two branches of Atlantic Water (AW) between the confluence zone (north of St.Anna Trough) and the central Laptev Sea due to isopycnal and diapycnal mixing between branches. Detailed measurements during this cruise demonstrated particularly intensive transformation on the transit between cape Arkticheskiy (95ºE) and 110ºE. By reaching the meridian 110ºE the upper temperature maximum in the Fram Strait branch of AW is completely gone and the warm core is shifted to ~250 m depth. Another prominent feature of 2013 thermohaline structure is strong near surface temperature maximum in the Atlantic sector, where ice free conditions were observed for a long time during this summer. For example, in St.Anna Trough the thickness of the surface mixed layer exceeded 40-50 m, and its temperature was up to 5ºC over the freezing point. At some CTD casts the upper boundary of AW (if counted by zero-degree isothermal) almost merged with the warm surface layer, which may substantially precondition the next winter ice formation in this area. 81N 90E 95E 105E 110E 126E 142E

Fig.9. Dissolved oxygen (upper panel) and temperature sections carried out during the cruise

4.4 Hydrochemical sampling and measurements (Rob Rember)

4.4.1 Sampling Rationale and Proposed Work for Hydrochemical Observations

Shelf-basin interactions in the EB are among key processes affecting water-mass structure [e.g. Aagaard et al. 1981; Martin and Cavalieri 1989]. For example, formation and maintenance of Atlantic- origin halocline waters, particularly the role of shelf waters is of great concern because to a degree, the cold halocline insulates the sea ice from the warm AW over much of the ocean. Initial work suggested these waters were formed on the Siberian shelves via brine rejection during ice formation and subsequent advection offshore [Aagaard et al. 1981; Steele et al. 1995]. Also, freshening of Atlantic waters via interaction with sea-ice melt (SIM) upon entry to the Arctic Ocean and subsequent winter convection have been invoked to explain halocline water formation [Rudels et al. 1996]. The advective- convective mechanism of lower halocline water (LHW) formation adapts the convective formation to allow for potential contributions of dense shelf water from the Barents Sea and/or winter polynyas [Steele and Boyd 1998]. In contrast, Kikuchi et al. [2004] argued the formation of LHW does not require a shelf water influence. Instead, they suggest the initial exposure of AW to freezing conditions upon entry into the Arctic Ocean can be sufficient to restrict any subsequent vertical mixing, such that additional buoyancy flux is unnecessary. These mechanisms differ in the role of shelf waters in LHW formation. Shelf waters are characterized by a large contribution of meteoric water (MW = river runoff+precipitation) and brine. A halocline layer requiring a shelf water influence, via either direct mixing or injection into overlying layers, will contain significant contributions from MW and brine. In contrast, waters formed solely by convective mixing would lack a MW influence and might be expected to have a higher SIM contribution. Contributions of MW and SIM (or brine) to the halocline are thus expected to vary depending on the formation mechanism. Such differences have been recently exploited by Bauch et al. [2011] to differentiate between convectively-formed halocline waters produced on (polynyas) and off (open water) the shelf. Similar techniques can be used to assess changes in the interaction between AW branches and shelf waters. Differences in the interaction among shelf waters, AW, and sea ice should also impact the distribution of NO. “NO” is a quasi-conservative tracer in waters isolated from exchange with the - atmosphere, where NO = 9 x [NO3 ] + [O2] [Broecker, 1974]. A minimum in the NO parameter that had been associated with LHW [Jones and Anderson 1986; Wilson and Wallace 1990] was explained via the uptake of resident nutrients and loss of excess dissolved oxygen via gas exchange during summer photosynthesis. Recent work by Alkire et al. [2010] has shown the utility of high-resolution vertical profiles of NO for assessing variability in Atlantic-origin halocline waters. Hydrographic surveys conducted in the Makarov and Amundsen basins during spring 2007 and 2008 revealed that minimum NO values were not associated with LHW in the Makarov Basin (MB), but were instead coincident with overlying cold halocline water, suggesting a direct role of Siberian shelf waters in their formation. They linked the shift in the NO minimum toward shallower halocline waters with an eastward diversion of shelf waters along the Siberian slope similar to that reported by Steele and Boyd [1998]. Continuous surveys are needed to study how NO distributions will continue to change as the interaction between shelf and Atlantic waters varies.

4.4.2. Dissolved oxygen, nitrate, barium and stable oxygen isotopes (M. Alkire, R. Rember)

Dissolved oxygen During the 2013 NABOS cruise, 175 dissolved oxygen samples were collected to calibrate the -1 SBE43 O2 sensors. Precision was estimated to be ± 0.03 mL L determined from random duplicate samples (n = 16) drawn from the same Niskin bottles. These data were used in combination with salinity and temperature taken from the bottle files logged by the CTD to calibrate the Seabird SBE43 oxygen sensors. Direct measurements of dissolved oxygen via Winkler titration can be used to check (or modify) factory calibration coefficients used to compute dissolved oxygen concentration from sensor output (voltage). Figure 1 shows a comparison of the Winkler O2 data (normalized by phi, a parameter determined from the corresponding CTD temperature and pressure as well as the applied calibration coefficients) and the sensor voltages recorded by the SBE43 sensors. The correlation coefficients of the linear regressions were excellent: R2 = 0.98751 and 0.9774 for sensors 1 and 2, respectively. Furthermore, the available data suggested that the sensor response was quite close to that expected from the factory calibration (see Table 1) and did not drift significantly over the course of the cruise. Table 4 Calibration coefficients (Soc & Voffset) for SBE43 oxygen sensors. The "old" coefficients were those supplied by Seabird whereas the "new" coefficients are those derived from the data comparison shown in Fig. 10

Sensor 1 Sensor 2 New Soc 0.4929 0.4092 New Voffset -0.3978 -0.3859 Old Soc 0.4911 0.4113 Old Voffset -0.4698 -0.4912

Fig. 10. Calibration/performance of SBE43 oxygen sensors.

Stable oxygen isotopes and dissolved barium A total of 1254 samples were collected for the determination of the stable oxygen isotope ratio of the water (18O), focusing on the halocline layer (33.5 < S < 34.7). The scintillation vials are properly sealed and parafilmed. These will be transported from Kirkenes via checked baggage and dropped off at the mass spectrometer laboratory facilities at Oregon State University for analysis. The data from these samples will be used to determine contributions of meteoric water (i.e., river runoff and precipitation) and net sea ice melt (meltwater or brine) to the cold halocline layer and lower halocline water at very high resolution (Fig. 2). Random replicates (n = 16) were collected over the duration of the cruise. These will be used, in combination with random duplicate runs of the same samples in the laboratory, to determine the precision of the resulting 18O data. Alongside the oxygen isotope samples, 880 samples were collected for dissolved barium analysis. These samples will be transported back to the University of Alaska, Fairbanks for analysis at the trace metal facility at the International Arctic Research Center. The samples will be analyzed in a Thermo Element2 inductively coupled plasma mass spectrometer after having been diluted 10 fold and spiked with an enriched isotope of barium.

Fig. 11. Distribution of δ18O samples collected over depth. Additional samples that were collected from greater depths were labeled separately and are not included in this plot. Nitrate The Submersible Ultraviolet Nitrate Analyzer (SUNA) was deployed with the CTD-O2 unit during 72 casts or 62 % of the total number of stations occupied during the cruise. The majority of the stations that were not sampled using the SUNA were a consequence of profiling to the bottom in deep water since the external battery pack is rated to a depth of only ~1000 m. Some stations were purposely occupied without the SUNA in order to conserve batteries for locations deemed more essential to addressing the hypotheses stated in the proposal. In subsequent cruise years, additional sets of batteries will be brought to ensure broader station coverage. Despite the somewhat reduced station coverage, preliminary processing of the SUNA data files suggests the instrument performed well and yielded high quality profiles of nitrate in the water column. The SUNA measures the absorption of ultraviolet light in the wavelength range 217-240 nm over a path length of approximately 1 cm. Inorganic species dissolved in seawater such as nitrate (NO3), nitrite, sulfide, and bromide absorb in this wavelength range as well as colored dissolved organic matter (CDOM). In regions of the ocean that are not impacted by hypoxia such as the Siberian slope and open Arctic Ocean, the absorption by sulfide and nitrite species can be ignored. A linear baseline correction is applied to the collected spectra to account for ultraviolet absorption by CDOM; this linear correction is generally suitable for seawater with relatively low concentrations of CDOM (Sakamoto et al., 2009). The shift in nitrate concentrations reported by the SUNA are expected to be < 0.6 mM per mg CDOM L-1 (Satlantic, 2013). Additional interference due to turbidity is also expected to be quite low in open ocean conditions: < 0.01 mM shift in NO3 per mg L-1 (Satlantic, 2013). Thus, the only two species in our study region that should significantly absorb in the wavelength range measured by the SUNA are nitrate and bromide. The absorption due to bromide can be subtracted from the measured spectra if temperature and salinity measurements are known, resulting in improved accuracy and precision of nitrate concentrations. The SUNA was interfaced directly with the CTD-O2 system such that the data files recorded by the Seabird sensor package included nitrate concentrations. While useable, these data were not corrected for the bromide absorption as the communication between the SUNA and CTD was only one way (SUNA output to CTD). Application of the bromide correction improves precision of the nitrate concentration measurements from 2.4 mM to better than 0.3 mM. Therefore the raw SUNA data was downloaded directly from the instrument and the spectra records matched to the CTD data using time synchronization. These synchronized data files were then processed using the algorithms reported in Sakamoto et al. (2009) to correct the data from bromide absorption. The resulting nitrate concentrations collected during the downcast of the CTD-O2-NO3 sensor package will be further checked for data quality (e.g., additional calibration against nitrate concentrations from discrete samples collected using Niskin bottles) and disseminated online for broad public use. After this additional data processing, the NO3 concentrations derived from the SUNA can be paired with sensor-based measurements of dissolved oxygen from the CTD-O2 package to compute the semi-conservative NO parameter, where NO = (9xNO3) + O2 (Alkire et al., 2010). This parameter can be useful in testing hypotheses of lower halocline water formation (NO < 400 mmol m-3 and 34 < S < 34.5) and modification along the Siberian continental slope (Fig. 3).

Fig. 12. Sections of temperature, salinity, dissolved oxygen, and nitrate along a southwest-to-northeast aligned transect line extending from ~81.5ºN, 95.6ºE to 82.5ºN, 98ºE. Plots were constructed using Ocean Data View (Schlitzer, 2001).

4.4.3. Nutrients and Dissolved Inorganic Carbon

Nutrients A total of 1330 water samples for nutrient analysis (nitrate, nitrite, ammonium, urea, phosphate and silica) were collected from 116 station along multiple transects in the East Siberian, Laptev, Kara and Barents Seas from 23 August to the 19th of September 2013. Sampling occurred at standard depths (surface, 10m to 100m by 10 m increments; 120m, 150m, 200 m, 250 m and 500 m). Seawater was collected from Niskin bottles into 20ml plastic vials and stored at -23°C until the end of the cruise then shipped from Kirkenes, Norway to the University of Alaska, Fairbanks for analysis using the Alpkem Model 300 Rapid Flow Nutrient Analyzer. The original plan was to analyze these samples during the cruise which would have allowed for samples at all depths to be collected. However, since analysis could not occur onboard, the number of nutrient samples was constrained by the number of bottles brought to collect samples. Therefore the number of depths per station was reduced to intensive sampling above 100m and included deeper depths initially (200 m, 250m and 500 m). Half way through the cruise the number of bottles for the left over transects was assessed, after which sampling was reduced to surface, 10 m to 100 m by 10 m increments and included 150 m. In addition to regular sampling at each transect, triplicate calibrations samples were collected after deployment of three MBARI-ISUS (Satatlantic LP) nitrate sensors that were attached to M1-4, M5.5 and M9 moorings.

Dissolved Organic Carbon (DIC) A total of 255 samples were collected from 52 of 116 stations for dissolved organic carbon from 23 August to the 19th of September 2013. Every other station was sampled in order to broadly sample all transects in the East Siberian, Laptev, Kara and Barents Seas. Sampling occurred at standard depths (surface, 10 m, 20 m, 50 m and 100 m). These water samples were fixed with saturated mercuric chloride solution and will be shipped from Kirkenes, Norway to the University of Alaska, Fairbanks for analysis.

4.4.4. Chlorophyll and Fluorescence Measurements

Chlorophyll a measurements. Estimates of chlorophyll a serve as a proxy for phytoplankton abundance. During the cruise, 583 samples from 91 stations were processed for assessing total chlorophyll. Typically, samples were collected from surface, 10m, 20m, 30m, 40m and 50m. This data can be used to compare fluorescence profiles collected on the CTD package and estimate integrated chlorophyll a for regional comparisons. In addition, another 142 size fractionation samples were collected in order to assess the size distribution of the chlorophyll-bearing cells. These size fractions are composed of the large cells, usually diatoms (>20 um), medium cells, usually small diatoms and flagellates (<20 um but >5um) and the small cells, the picoplanktonic cells (<5um). 583 samples 142 Fractionations

Assessment of Phytoplankton-photo-physiology. Two fast rate repetition fluorometers (FIRe system and FAST Ocean system) were used during the cruise to provide a range of photo-physiological characteristics at high sensitivity in vivo. These characteristics include: the normalized active fluorescence (Fv/Fm), which is a measure of the efficiency of the conversion of light energy into chemical potential (photosynthesis) and is related to the availability of nutrients in the field; the cross section of photosystem II (sPSII), which is a measure of the size of the light-harvesting antenna system associated with the photochemical reaction center PSII; and a measure of total chlorophyll a (Fm). More than 500 fluorescent measurements were made during the cruise with approximately 80 depth profiles. Measurements will be analyzed with respect to nutrient fields and primary productivity estimates.

4.4.5. Carbon and nitrogen productions of phytoplankton

To estimate carbon and nitrogen uptake of phytoplankton at different locations, productivity experiments were executed by incubating phytoplankton in the incubators on the deck for 4-5 hours 13 15 15 after stable isotopes ( C, NO3, and NH4) as tracers were inoculated into each bottle. Total 19 productivity experiments (Table 1 and Fig. 1) were completed during this cruise. At every productivity station, the productivity waters were collected by CTD rosette water samplers at 6 different light depths (100, 50, 30, 12, 5, and 1%). After the incubation, all productivity sample waters were filtered on GF/F (ø = 25 mm) filters for laboratory isotope analysis at University of Alaska Fairbanks after this cruise. Along with the productivity bottle experiments, 15 macromolecular composition of phytoplankton experiments for three depths (100, 30, and 1% light depths) were executed to study the physiological status. These filtered (GF/F, ø = 47 m) samples will be chemically analyzed for the macromolecular composition (such as lipids, proteins, carbohydrates) of photosynthesis.

Table 5 Sample list for 2013 NABOS cruise St. Carbon production Nitrogen Macromolecular production composition 2 √ 5 √ √ √ 6 √ √ 11 √ √ √ 15 √ 19 √ √ √ 24 √ √ 33 √ 36 √ √ √ 41 √ √ 44 √ √ 49 √ √ 57 √ √ √ 61 √ √ √ 68 √ √ √ 71 √ √ √ 72 √ √ 80 √ √ √ 91 √ √ √ 95 √ √ 100 √ √ √ 116 √ √ √

Fig. 13. Stations for primary productivity during the 2013 NABOS cruise.

4.4.6. NO3- N and O isotopes

We will examine the δ15N and d18O of nitrate to help elucidate the nitrogen cycling dynamics in the eastern Arctic Ocean. We focused sampling on transects moving from open water across the slope to the shelf in order to understand N sources to and processes affecting the productive shelf. We collected a total of 320 samples from 22 profiles. We also hope to observe differences in the nitrate N and O isotopic signals of the different water masses in the region due to degree of biological modification along their pathways, particularly in the region of the Santa Anna Trough. Samples will be analyzed using the 'denitrifer' method, wherein denitrifying bacteria lacking terminal nitrous oxide reductase quantitatively convert sample nitrate to nitrous oxide, the N and O isotopic composition of which will be measured by gas chromatography-isotope ratio mass spectrometry.

4.4.7. Silicate and methane measurements

Detailed study of methane distribution reflects contribution of changes in the hydrological cycle over the shelves and alteration of terrestrial carbon cycles to formation and propagation of halocline water and affect the hydrological and biogeochemical parameters of the shelf waters. That as well quantify the Eurasian Shelf Seas contribution of methane to the atmosphere. It is known that huge of submarine methane are stored in hydrates, source rocks and permafrost sediments on the Eurasian Arctic shelf and when released causes excess methane in shelf water, as was observed in the Laptev and East Siberian Sea [Shakhova and Semiletov, 2007] as well as in the Barents Sea [Lammers et al., 1994; Damm et al., 2005]. Plume spreading in the stratified shelf water transports dissolved methane mainly along isopycnals into the deeper and dense shelf water but methane also escapes into surface water by vertical mixing [Jeong et al., 2004; Damm et al., 2005]. However, offshore transports of dissolved methane are rapidly reduced by open ocean dispersion, sea to air flux and methane oxidation processes and so it would be expected that methane flows must be fixed locally just next to its sources. Combined with nutrient measurements (nitrogen, phosphorous) methane data could be used to reveal genesis of methane [Karl et al., 2008; Damm et al., 2010] as well to trace spreading of plums. Silicon concentration is used for trace of water masses (Atlantic, Pacific, rivers) and as an indicator of productive resources. Dissolved silicon (Si) measurements were performed at 115 stations on eight cross-sections (was measured using 2414 samples). Water samples for methane measurement were collected at 132 stations as well samples for methane isotopes were collected.

Fig.14. Samples location. Black circles show CTD-stations with Si measurements, red circles show stations for methane sampling.

Silicate sampling and analysis: Si 500 mL plastic bottles were used for sampling. Bottles were rinsed three times with sea water before collection. Samples were analyzed immediately after sampling (for 1-1.5 hour) on board using the colorimetric methods following SIO RAS, 1992 (method based on Koroleff F. 1972. Determination of dissolved silicate // Cooperative Reseach Rep. ICES Series A. №29. P.87-90). Precision of the analysis at concentration 4.5 μmol is 4%, at concentration 45 μmol is 2.5%. We used an Unico 1201 Spectrophotometer. The analysis was calibrated using the set of standards (Na2SiF6) as it’s shown at Fig 2. Stock standard solutions prepared in Milli-Q water were used to produce working standards. In turn, working standards were prepared in surface sea water with negligible silicate concentration.

Fig. 15. Calibration curves on 23.08.2013 and 13.09.2013.

Methane Water samples for measurement methane concentration was collected into 30 ml, 100 ml, 200 ml calibrated glass vials after three times rinsing with sea water. 5 ml, 20 ml and 40 ml of sampled water respectively have been forced out. Remaining samples was alkalized to pH 12, actively shaken then sealed for following testing in Moscow using a gas chromatograph with a flame ionization 13 detector (Shimadzu, GA-8A). As well we have taken samples for δ C-CH4 to following quantify using a Delta XP plus, Finnigan mass spectrometer.

Preliminary results show typical silicate distribution for finalization of vegetative period with some local specifics along remote sections. Negligible silicate concentration (often less than detection limit of the measuring method) in the surface layer presented by poor Atlantic water has been observed along western shallow sections near c. Arcticheskii, Severnaya Zemlya Island). In the direction of an ice edge silicon concentration is weakly increases. In the surface Eastern and Central Laptev Sea perceptible silicate concentration appear due to river discharge. To the east of Lomonosov Ridge in the surface layer of the East Siberian Sea silicate concentration became higher but remain at the limit range for plankton growth. Besides rivers discharge appreciable Pacific water penetration is perceptibly here. Silicate concentration in the deep water does not exceed 13 umol. Range of silicate concentration in the Atlantic water is 4.7 – 5.2 umol. This water is traced along continental slope. Barents Sea water is characterized by little more silicate concentration. Detailed analysis silicate data requires combination with other measured biogeochemical and thermohaline parameters.

Fig. 16. Silicate concentration at different sections

4.4.8. Water sampling for DOC/POC, n-alkanes and mass concentrations of particulate matter

Fig. 17. NABOS 2013 station map. Black circles – all NABOS 2013 stations, red circles – DOC/POC water sampling, green circles – DOC/POC, n-alkanes and mass concentrations of particulate matter sampling.

To study distribution of organic carbon and composition of n-alkanes in dissolved and particulate organic matter, its sources and transformation processes, we have collected 193 water samples at 22 stations. Sampling was performed at 4 sections (I – IV) in Laptev and Kara seas, as shown on Fig 17. Within each section water samples were taken at 1-2 stations for DOC/POC, n- alkanes and mass concentrations of particulate matter analysis (Fig.17, green circles) and 3-5 stations for DOC/POC analysis only (Fig.17, red circles). List of our sampled stations is summarized in Table 6. Table 6. Sample station list Sampling type Transect Station Particulate DOC/POC n-alkanes matter AF13-001 + AF13-008 + + + AF13-013 + AF13-018 + I AF13-020 + AF13-025 + + + AF13-060 + AF13-030 + AF13-032 + II AF13-034 + + + AF13-038 + AF13-042 + AF13-070 + AF13-072 + III AF13-076 + + + AF13-079 + AF13-081 + AF13-097 + AF13-099 + IV AF13-102 + AF13-107 + + + AF13-114 + +

4.4.9. Water sampling for carbon, nitrogen and phosphorus

Our task was determination of dissolved organic matter (dissolved organic phosphorus, dissolved organic nitrogen and dissolved organic carbon) in the Arctic waters. Water samples were taken at the standard depths (0, 100m to 150m by 10 m increments; 150m, 200m, 250m, 500m, 750m, 1000m, 1500m, 2000m, 3000m) and additional samples at the depths of the fluorescence maximum, temperature and oxygen extremes.

Table 7 Total water samples Collected for C/N/P determination

PO ’’’ P N , C 4 org org org Stations 112 64 64 Depths all All 5-10 Total water samples 2401 1261 438

During the cruise 116 hydrological stations were sampled. Mineral and organic phosphorus was determined in the hydrochemical laboratory aboard RV “Akademik Fedorov”. Phosphates were determined by spectrophotometric method (λ=885 nm) of Murphy and Riley (Murphy, Riley, 1962) using a UV-1601PC Spectrophotometer (Shimadzu) at all depths of 112 stations. Organic phosphorus was determined by the Koroleff method (Koroleff, 1972). This method converts all the organic phosphorus into mineralized phosphorus. Then total phosphorus was determined by the Murphy and Riley method (Murphy, Riley, 1962). Organic phosphorus was calculated by the formula: Porg=Ptot-Pmin. Organic phosphorus was determined for all depths of 64 stations.

Fig. 18. Locations of the stations NABOS-2013 for organic matter (C/N/P) and mineral P

The water samples for the dissolved organic nitrogen and dissolved organic carbon were collected at surface, 30m, 50m, 100m to 150m (by 10 m increments), 250m, 1000m and bottom of 64 stations. Then the water samples were filtered using the combusted GF/F filters (Whatman) and preserved using HCl to be analyzed the Shimadzu TOC Vcph at the Hydrochemical laboratory of VNIRO in Moscow. Total water samples collected for determination of C/N/P during the NABOS-2013 is shown in Fig. 18.

4.5. Air-sea interaction

The following objectives defined the design of our experiments and the choice of instrumentation:  Measure the surface heat budget. Analyze energy exchange between atmosphere and surface using measurements of turbulent fluxes (latent and sensible heat fluxes, momentum fluxes) and radiation fluxes in the subsurface layer of the atmosphere under different stability conditions.  Analyze the temperature and structure characteristics of the surface and its influence on atmospheric boundary layer structure. Validation of satellite-derived surface temperatures and temperature profiles. Studies of the oceanic thermal skin layer. Improvements to satellite measurements of surface temperature in the infrared and the microwave.  Define the exchange coefficients in the aerodynamic bulk formulas, the surface roughness parameter with respect to the type of the surface and meteorological conditions.  Observation the atmospheric condition and boundary layer dynamic in marginal ice zone by remote sensing and contact techniques. Studies of Arctic Cloud Radiative Forcing.  Collection of data on CH4 and CO2 concentrations along the Arctic continental shelf, where methane hydrate deposits are predicted. Validation satellite methane data.  The investigation of time-space variability of atmospheric ozone and aerosol. The study of optical, microphysical and chemistry properties of Arctic aerosol.

A suite of observations was carried out during the cruise:  Direct measurements of temperature, horizontal and vertical components of wind speed and humidity, carbon dioxide and water vapour concentration above sea and ice surfaces of various conditions. The data are used for calculation of turbulent fluxes, as well as roughness parameter of a surface and atmospheric stability.  measurement of sea surface temperature in the infrared (IR) range;  standard meteorological measurements.  Remote sensing measurements of temperature profiles in atmospheric boundary layer (0- 600 m)  Measurements of sea and ice surface structure by radar  Observations of vertical profiles of temperature, relative humidity, pressure and wind from bottom to upper air by radiosondes.  Measurements of methane, carbon dioxide and water vapor concentration during all trip.  Registration of the ship motion (direction, velocity, angle accelerations, angles of slope)  Visual observations of cloud conditions  Total electron content (TEC) in the atmospheric column  Measurements of radiation budget (downward and upward longwave and shortwave radiations)  Video and photo sea state registration  Measurements of aerosol optical depth  Measurements of the total atmospheric ozone content  Collection of aerosol probes by filters  Measurements of the air black carbon concentration  Measurements of aerosol particles concentrations and size distributions

Equipment To carry out the measurements described above, the following equipment was used: . A USA-1 Sonic thermo-anemometer (METEK Co.) that measures fluctuations of three components of wind speed and temperature fluctuations at frequency of 10-50 Hz. . A Windmaster Sonic thermo-anemometer (Gill Co.) that measures fluctuations of three components of wind speed and temperature fluctuations at frequency of 10-50 Hz. . Two level automatic weather station AWS2700 (AANDERAA). This is a self-contained system that measures air temperature and humidity, wind speed and direction, surface air pressure and shortwave (λ ~ 0.3-3μm) incident radiation. . Microwave radiometer for atmosphere temperature profile MTP-5. (АТЕХ). . kipp&Zonen radiation complex (two pyranometers CMP21 and two pyrgeometers CGR-3) . GPS Radiosondes for atmospheric profiles (MEISEI, RS-06G). . GPS two-frequency receiver EFT M1 GNSS. . A inclinometer and three axis accelerometers and rate gyros to measure ship motions in three dimensions. . A GARMIN GPS 17-HVS navigator to measure the ship‟s position. . Open path infrared gas analyzer LI-7500 (LICOR Co.), measuring H2O and CO2 with frequency of 10-20 Hz. . Video camera (web cam) to the sea surface conditions visual control. The images were recorded by a laptop computer for subsequent analysis. . LOS GATOS RESEARCH (LGR) Greenhouse Gas Analyzer and Fast Greenhouse Gas Analyzer, Rackmount, with Enhanced Performance (Models 911-0010) . Nefelometer (aerosol particles meter) GRIMM (model 1.108) for aerosol particles control and Aethalometer for black carbon concentration. . Ozonemeter M-4 . Fotometer for optical aerosol depth . A number of aerosol probes for different aerosol properties. . Ship radar Icom 1200RII with digital block. . IR-radiomerer HEITRONICS KT19 II

All equipment was installed to optimally reduce the dynamical and thermal ship body effects. After high-frequency noises and low frequency trends are filtered out, ship motion correction is applied to the wind velocity data. For the temperature signal, it is well calibrated and sound virtual temperature effects can be reduced later. After these correction procedures, 10 minutes eddy fluxes and statistics are obtained in real-time and filed as well as row turbulence data. For calculation of turbulent fluxes an eddy-covariance (or eddy-correlation) technique was used.

Table 8 Data description Data Measurement Format Frequency period GPS-record August 22 – ASCI 1 min September 21 Meteorological data August 22 – ASCI, Excel 1 min September 21 Gill wind velocity and August 22 – ASCI, Excel 10 Hz temperature data September 21 USA wind velocity and August 22 – ASCI 10 Hz temperature data September 21 Turbulent sensible, latent August 22 – ASCI 10 min heat and carbon dioxide September 21 fluxes LiCorr CO2 and H2O August 22 – ASCI 10 Hz concentrations September 21 Video camera August 22 – Avi files September 21 downward and upward August 22 – ASCI, Excel 1 min longwave and shortwave September 21 radiations IR radiometer (surface August 22 – ASCI 1 sec temperature) September 21 Atmospheric August 22 – ASCI 5 min temperature profiles (0- September 21 600 m) Atmospheric 28 - 31 August ASCI 6 hour, 47 temperature, wind 3 - 8 September soundings velocity and direction and humidity profiles Radar images August 22 – ASCI 15 min September 21 jpg Photo sea surface with August 22 – jpg 625 images polarizing filter September 21 Aerosol probes August 22 – 6 hour, 120 September 21 probes mass concentration of August 18 – ASCI 630 probes black carbon, aerosol September 20 number concentration Common ozone content August 17 – ASCI 12-24 hour September 20 Methane and carbon August 20 – ASCI 1 Hz dioxide concentration September 22

Preliminary results:

10

C 0

0 Tair,

-10

5

C 0

0 dT(s-a) -5 100

90 f, % f,

80 1030 1010

P, hPa P, 990

20

10 Wind,m/s 0 235 239 243 247 251 255 259 263 Julian day

NORTH

15%

10%

5% 22 - 24 20 - 22 WEST EAST 18 - 20 16 - 18 14 - 16 12 - 14 10 - 12 8 - 10 6 - 8 4 - 6 2 - 4 0 - 2 SOUTH

Fig.19. meteorological conditions during cruise

2 40

20

0

sensibleheat, W/m -20

2 40

20

0

Latentheat, W/m -20 0.8

0.6

0.4

, m/s ,

* u 0.2

0 235 238 241 244 247 250 253 256 259 262 Julian day

Fig. 20. Turbulent heat fluxes and wind speed along the route

a) Sensible heat b) latent heat 50o E 75o E 100o E 125o E 150o E 50o E 75o E 100o E 125o E 150o E 35 o 84 N 30 35 84o N 25 30 20 25

o 15 20 81 N o 81 N 10 15 5 o 10 78 N o 0 78 N 5 -5 o 75 N 75o N 0 -10

o -5 72 N -15 72o N -10

Fig. 21 Spatial distribution turbulent fluxes

350

2 300 W/m 250 Fdown Fup 200

400 Qdown

2 Qup

W/m 200

0 Qnet Fnet

2 B

100 W/m 0

-100 30 20

h, degrh, 10

0 235 238 241 244 247 250 253 256 259 262 264 Julian day

Fig.22. Surface radiation budget during cruise

60

Lnet 40 Qnet H+HL 20

0 2

W/m -20

-40

-60

-80 235 238 241 244 247 250 253 256 259 262 264 Julian Day Fig. 23. Energy balance during cruise. Qnet – long wave radiation budget. Lnet – short wave radiation budget, H and HL – sensible and latent heat fluxes from measurements.

Fig.24. Thermal structure of atmospheric boundary layer along the route

Fig. 25. Radar imagines of (a) wind waves, (b) broken ice, (c) ice with leads. 50o E 75o E 100o E 125o E 150o E

84o N

81o N

78o N

75o N

72o N -3 -2 -1 0 1 2 3 dT, 0 C

Fig. 26 Difference between the surface and air temperatures.

Fig. 27. Hourly mean CH4 concentrations along the route between August 22 and September 11, 2013. Lines of equal ocean depths are drawn for the depth: 3000, 2000, 1000, 500, and 300 m.

5. Summer School aboard “Akademik Fedorov”

Important outreach component of the 2013 cruise was the Summer School, which provided an excellent opportunity for 20 graduate students, PhD students and early career scientists from US, Europe and Russia to learn about the climate change in the Arctic and to participate in field experiments onboard. The Summer school was sponsored by: • National Science Foundation • Russian Foundation for Basic Research • International Arctic Research Center • Obukhov Institute for Atmospheric Physics • Russian Academy of Sciences Co-directors of the Summer school were Irina Repina and Vladimir Alexeev. IARC Summer Schools started in 2003 and at least one school per year has been organized since then. Two summer schools had oceanographic focus so far – in 2005 and 2006. This summer school was titled “Climate Change in the Arctic Ocean”. 21 students from USA, Russia, Belgium, Finland, Norway and Sweden were chosen in the selection process. Four instructors and one media person, also involved in the instructional activities contributed to the summer school program. NABOS expedition members actively participated in the program by contributing with lectures and hands-on activities. Many NABOS expedition members attended summer school lectures as well. Students worked with expedition on studying various observations conducted as a part of the NABOS program. 55 lectures in total were given to students during one months of the cruise. Student groups were formed to work on the following projects: - WRF model (4 flavors): - Arctic Cyclone of 2012 - WRF + NEMO-LIM - Arctic Dipole - Extreme Weather - Arctic Sea ice model - Planetary boundary layer observations - Hydrology observations - Sea ice forecast

The outcome of the summer school was very productive with a potential for at least two articles that could be published as a result of work on projects.

6. Summary

The NABOS 2013 cruise program was successfully fulfilled. New unique scientific data were collected along the Eurasian continental margin. Preliminary analysis shows that warmer (relative to the climate mean of 1950-1990) state of Atlantic Water in the Arctic Ocean remains, despite some cooling after the maximum, reached in 2006-2007. Outstanding feature of 2013 thermohaline structure is strong near surface temperature maximum in the Atlantic sector, where ice free conditions were observed for a long time during this summer. At several instances the upper boundary of AW (if counted by zero-degree isothermal) almost merged with the warm surface layer, which may substantially precondition next winter ice formation in this area. Extended nomenclature of hydrochemical sampling, carried out during the cruise could only be done under lab facilities provided onboard R/V “Akademik Fedorov”. Important technological novelty in this cruise was the deployment of the cluster of moorings along 126ºE. This cluster completely covers the AW flow in this area, thus allowing accurate calculation of discharge and estimation of variation of major physical properties. Five ITP buoys were deployed in climatically important region of the Arctic Ocean. The glider, which was launched far in the north, was probably the first attempt of such sort in high Arctic. Although the glider operated for a short time before its signal was lost, the information that was received proves the efficiency of extended usage of autonomous underwater vehicles in future Arctic studies. Complex studies of ocean-air interaction were carried out around the clock with variety of high- tech devices. A unique data on turbulent heat fluxes, structure of atmospheric boundary layer, aerosol composition, methane fluxes etc. were collected in the MIZ area. Ice observations during the cruise allowed precise mapping of ice cover properties along the route and appeared to be crucially important for efficient ice navigation and for finding locations for ice buoys deployments. Summer school onboard the ship provided an excellent opportunity for graduate students, PhD students and early career scientists from the USA, Europe and Russia to learn about the climate change in the Arctic and to participate in field experiments.

Fig. 28. Expedition –Summer school group photo in Kirkenes (September, 22, 2013)