Cruise Report R.V. Oceania, AREX2004

Transcription

1 Powstaców Warszawy, PL Sopot, P.O. Box 68 November Cruise Report R.V. Oceania, AREX4 Ship: Cruise: R.V. Oceania Arex4 Dates: Port Calls: Sopot (Poland) Longyearbyen (Spitsbergen) Number of Scientist 11 Chief Scientist Principal Project Research Area prof. Jan Piechura ASOF-N, WP1 Greenland Sea

2 WP1. Atlantic Water pathways in the Greenland Sea Waldemar Walczowski, Jan Piechura, Robert Osiski, Piotr Wieczorek, Ilona Goszczko (IO PAS) 1. Introduction Institute Oceanology Polish Academy of Sciences is doing oceanographic research in the Norwegian, Greenland and Barents Seas since During summer cruises hydrographic data were collected, some at the same permanent stations and transects. Since 1993 the ADCP data has been collected, since 3 the lowered ADCP measurements have been introduced. Measurements were conducted within the Atlantic Domain. In the Greenland Sea domain is situated between Barents Sea slope and underwater ridges system Mohns Ridge and Knipovich Ridge. Due to convergence of the isobaths in the northern part, AW domain forms wedge, wide in southern part and narrow in the northern end. Specific bottom topography meaningfully influences the currents pattern and structure. Coverage in the southern part of investigated area is spare in comparison to the northern one. This causes less accurate horizontal distribution of properties in the region south of the Bear Island. Our main afford was concentrated in the northern part of Atlantic Domain, where processes controlling the AW inflow into Arctic Ocean through the Fram Strait and the westward recirculation take place.. Observations 4 AREX4 cruise of the R.V Oceania was performed in period of June 8 4 July CTD (conductivity, temperature, depth) profiles along 1 sections were done (Fig 1, Tab.1). Sections were situated perpendicular to the supposed direction of the Atlantic Water flow. Some transects were repeated two or even three times (section EB) to observe the short-term variability of hydrological fields and currents. For CTD measurements the Seabird SBI9/11plus probe was used. The probe was serviced before the cruise. Temperature and conductivity sensors were calibrated by the Sea-Bird Electronics service. Water samples collected by means of the rosette water sampler SBE3 were analysed at the ship and in IOPAS laboratory with the Guildline Autosal 84A. Measurements of currents were performed by means of lowered Acoustic Doppler Current Profiler (LADCP). The self-recording 3 khz RDI device was used to profile entire water column during the standard CTD casts. During the whole cruise continuous currents measurements by the shipmounted ADCP, RDI 1 khz were conducted.

3 Y6 Y Y4 Y3 Y Y U3 X1 X9 X11 X1 X13 X14 U4 EB-7 19 EB_11 Z1 Z11 Z1 Z13 X X7 Z9 X3 X1 EB_1 3 Z3Z Z Z7 Z8 Z S1 S14 S13 S11 S9 S7 S3 S1 S S6 76 N4 N3 N N- N-1 N N1 N-6 N-4 N-11N-1 N-8 O1 M4 O- O-4 O-6 O-7 O-8 O-9 O-1 O-11 O-1 O-13 H19 K16 H18 K1K11 K13 K14 K1 H17 H1 H16 H14 K1 H13 K9 H1 K K7 K6 K8 H1 H11 KK1 K4 K3 H8 H9 V33 V3 V31 V3 V9 V8 V7 V6 V V4 V3 V1 V1 H H6 H4 H7 H H3 V V19 V18 V17 V16 V1 H1 V14 V13 V1 V AH1 V1 V9 7 A18 A17 A16 A1 A14 A13 A1 A11 V8 V V6 V V4 71 V3 V V1 7 3 A1 A9 A8 A7 A6 A A4 A3 A A1 A Fig. 1. Stations grid performed during R.V Oceania cruise, summer 4. 3

4 Table 1. CTD stations carried out during Arec4 cruise. Running No. CTD- Station No. Cast No. Data Time (UTC) Latitude Longitude Water depth Corrected [m] 1 A :3: N E 7 A :3: N E A :4: N E 7 4 A :4: N E 34 A :31: N E 44 6 A :3: N E 7 A :4: N E 9 8 A :16: N E 66 9 A :1: N E 66 1 A :9: N E 6 11 A :: N 1.73 E 6 1 A :: N E A :7: N E A :4: N E 86 1 A :: N 9.81 E A :41: N 7.8 E 8 17 A ::3 7. N E A :: N E 9 19 A :39: N E 13 AH :6: N 3.11 E 73 1 H :: N E 8 H :3: N E 8 3 H :39: N 9.84 E 19 4 H :19: N 6 9. E 1 H :47: N E 31 6 H :: N E 7 H :4: N E 33 8 H :7: N E 9 9 H :17: N E H :4: N E H :3: N 13.1 E H :13: N E 1 33 H :14: N 1.6 E H :1: N E 48 3 H :8: N E H :6: N E 4 37 H :1: N E H :48: N E H :43: N E 43 4 V :7: N.8 E V :7: N E 1 4 V :1: N E V :7: N E V :6: N E 1 4 V :7: N E 1 46 V :6: N E 4 47 V :8: N E 6 48 V ::3 7. N E V :1: N E 3 V :9: N E 38 1 V :47: N E 4 V :7: N E 41 3 V :17: N E 4 4 V :39: N E 48 4

5 V :33: N E 3 6 V :7: N E 3 7 V :38: N E 13 8 V :1: N E 6 9 V :: N E 6 V :6: N 18.9 E 61 V :4: N E 6 6 V :43: N E 1 63 V :33: N E 64 V :3: N E 6 V :4: N E 7 66 V :44: N E 6 67 V :17: N E 6 68 V :3: 7 3. N 17.9 E 1 69 V :: N E 13 7 V :46: N E 1 71 V :1: N E 8 7 V :8: N E 3 73 O :3: N E M :3: N E 33 7 O :: N E 3 76 O :4: N E O :4: N E O :: N E 9 79 O :33: N E O :: N 13. E O :6: N E O :6: N E 9 83 O :6: N E O :33: N 8.6 E 38 8 O :33: N E O :6: N 6.9 E 6 87 O :: 7 4. N E 8 88 K ::7 7.8 N E K :49: N 6. E 88 9 K :43: N E K :3: N E 9 K :8:7 7.1 N E 9 93 K :3: N E 6 94 K :44:6 7.3 N E 4 9 K :36: N E K :14: N E K :11:4 7.6 N E K :16: N E K :8: 7.4 N 14.7 E 11 1 K :9: 7.7 N E K :3:4 7.7 N 1.77 E 81 1 K :43:9 7.1 N E K :39: N E 14 N :9: N E 17 1 N3P :9: N E 1 16 N :43: N E 7 17 NP :19: N E N :1: N E N1P :1: N E N :1: N E N :1: N E 1 11 N :47: N E 8

6 113 N :16: N E N :4: N E 9 11 N :7: N E N :11: N E N :38: N 7.4 E N :18: N E N :: N 6. E 8 1 N :3: N E N :: N 4. E 63 1 N-11_ :18: N 4.17 E N-11_ :9: N E S :46: N E 83 1 S :: N E 3 16 S :: N 1.3 E 3 17 S :34: N E 4 18 S :4: 77. N E S :: 77.4 N E 7 13 S9_ :9: N E S9_ :9: N E S :: N E S :: N 9 6. E S :36: N E S :6: N 1.1 E S :4: N E S :: N E S :3: N E S :19: N E 1 14 Z :6: N E Z :: N 1.34 E 6 14 Z :44: N E Z :31: N E Z :3: N 9.19 E Z :6: N E Z :3: N 8. E Z :8: N E Z :: N 6 4. E Z :: N 4.8 E 3 1 Z :8: N 1. E 7 11 Z :41: N 4. E 8 1 Z :1: N 49.8 E 3 13 U :38: N 1.9 E EB :3: N E 1 EB :49: N 1 9. E 4 16 Eb1a :44: 78. N E 4 17 EB_ :19: N E 3 18 EB_ :1: N E EB :36: N 3. E 9 16 EB_ :13: N 6.31 E EB :46: N E EB_ :: N E EB_ :3: N E EB_ :1: N E EB_ :16:3 78. N E EB_ :1: N E EB_ :8: N E 168 EB_ :11: N E 169 EB_ :17: N E 1 17 EB_ :3: N E 4 6

7 171 EB :8: N E EB_ :41: N E EB_ :1: N E EB :47: N E EB :3: N 6.97 E EB :39: N 3.83 E EB :: N E EB_ :9: N 4.9 E EB_1b :4: N E U :18: N E X :8: N 3. E X :4: N E X :4: N E X :: N 3.31 E X :7: N 6. E X :4: N E X :46: N E X :6: N E X :7: N E 9 19 X :43: N E 191 X :3: N 8.3 E 4 19 X3a :3: N E X :16: N 9.11 E X :1: N E 7 19 X :8: N 1.14 E Y :9: N E Y :44: N E Y :39: N E 199 Y :3: N 11.9 E 1 Y :47: N E 83 1 Y :: N E 17 Y :8: N E Y :3: N E 13 4 EB :6: N E EB :36: N E 6 EB :1: N E 47 7 EB :19: N E 98 8 EB :44: N E EB :: N E 14 1 EB :31: N E EB :18: N 6.94 E 44 1 EB :38: N 3.9 E 9 13 EB :6: N. E EB :6: N E Some preliminary results As in earlier cruises, during 4 cruise two northward flowing branches of Atlantic Water in the Greenland Sea were observed. The main branch of the West Spitsbergen Current flows along the Barents Sea continental slope and Spitsbergen shelf break. The second, colder and less saline branch continues along the Mohns and Knipovich Ridges as a jet stream of the Arctic Front. Due to the bottom topography, both branches of AW converge west of the southern Spitsbergen coast. Figure presents the distribution of temperature and baroclinic currents at depth 1 m (calculated for the reference level of 1 m.) during summer 4. To reduce effect of non-uniform data spacing, temperature and HD fields were smoothed 7

8 and filtered. Finally, the picture of general currents pattern was obtained, rather then synoptic snapshot. Considerable part of AW flowing along the Norwegian coast proceeds eastward into the Barents Sea, the rest continue northward as two separated branches. One branch is related to the Barents Sea slope. Even after data smoothing and filtrating, the mesoscale activity, especially along the Spitsbergen s shelf is pronounced. Separated warm eddy inflows into the Arctic Ocean. This effect may be partly caused by the non-uniform data distribution, but mesoscale activity has been also observed. Jet streams of the Arctic Front form the second branch of AW. This branch recirculates westward between 78º-79ºN. The general flow structure cross the section, obtained from baroclinic calculations, ADCP and LADCP measurements was similar (Fig.3), however baroclinic transports calculated from hydrological data and total transports from LADCP measurements differ a lot. Table presents transports across selected sections, calculated from detided LADCP data. It confirms the importance of barotropic fraction of the flows. Measurements performed by means of LADCP show that the structure of the flow is much more complicated (Fig 4, Fig ) than this presented at Fig.. The high temporal currents variability was observed directly this year. Currents changes seem to be relating to wind direction and induced by barotropic flows. The possible mechanism is that winds blowing along the Spitsbergen coast, due to the Ekman flow causes rising or lowering sea level. The sea tilt induces geostrophic barotropic current along the Spitsbergen coast. Measurements at the section EB were repeated 3 times (Fig 6). The structure and amount of the transport has changed considerably during 3 days between the first and second pass. During this time the wind direction has changed from the southern to northern one. Table Volume transports cross the selected sections. Positive transport indicates northward flow. Atlantic Water calculated against salinity S>34.9 psu, Temperature 3º C. Detaided data from LADCP were used. Section K (7 N) N (76 3 N) S (77-78 N) Z (78-78 ) EB (78 N) AW Vol. Net Vol. transport Northward Southward AW+ AW- AW Heat (Sv) Vol (+) Vol (-) (Sv) (TW)

9 Water temperature and baroclinic currents vectors. Year 4, level 1 m. Reference level 1 m Reference Vectors (cm/s) Fig.. June-July 4. Smoothed temperature distribution and baroclinic currents at 1 m. Reference level 1 m. 9

10 VM-ADCP BAROCLINIC Distance (km) EB_14 EB_13 EB_1a EB_11 EB_1 EB_9 EB_8 EB_7 EB_6 EB_ EB_4 EB_3 EB_ EB_1 LADCP Distance (km) Pressure (db) Pressure (db) Fig. 3. VM-ADCP currents (upper bar), geostrophic baroclinic currents and LADCP measured flows cross the West Spitsbergen Current. Section EB along the 78º N. R.V. Oceania, June 4. 1

11 79 Reference Vectors 1 cm/s cm/s Fig. 4. Water temperature and LADCP measured currents at 1 m. R.V Oceania, summer 4. 11

12 Water salinity and LADCP currents vectors. Year 4, level 6 m. Reference Vectors 1 cm/s cm/s Fig.. Water salinity and LADCP measured currents at 6 m. R.V. Oceania, summer 4. 1

13 Distance (km) Pressure (db) Distance (km) Pressure (db) Distance (km) Fig. 6. LADCP measured currents cross section EB. R.V Oceania, summer Pressure (db)