ALPHA HELIX CRUISE HX260

Thursday 20th June 2002- Saturday 29th June 2002

BERING STRAIT CRUISE REPORT

 

FUNDING SOURCE:     NSF-OPP-0125082 (Grebmeier, U of TN)

 

CHIEF SCIENTIST:       Rebecca Woodgate

                                         University of Washington, Applied Physics Laboratory

                                         1013 NE 40th Street, Seattle, WA 98105-6698.

                                         Phone:    206-221-3268

                                         Fax:        206-616-3142

                                         Email:   woodgate@apl.washington.edu

 

SCIENTIFIC PERSONNEL:

   Rebecca Woodgate                       APL, Moorings                            (F, Chief Scientist)

   Roger Andersen                             APL, Moorings                            (M)

   Terry Whitledge                              UAF, Nutrients & Sampler         (M)

   Sarah Thornton                              UAF, Nutrients & Sampler         (F)

   Sang Heon Lee                               UAF, Nutrients & Sampler         (M)

   Clara Deal                                      UAF, DMS sampling                  (F)

 

SCIENTIFIC PURPOSE:

This cruise had two main scientific goals. 

The first (and foremost) was the recovery and redeployment of moorings in the Bering Strait.  These moorings are part of a multi-year time-series (currently over 10 years long) of measurements of the flow through the Bering Strait.  The properties of this flow not only influence the Chukchi and Beaufort Seas, but can also be traced across the Arctic to the Fram Strait and beyond.  The long-term monitoring of the inflow into the Arctic Ocean via the Bering Strait is important for understanding climatic change both locally and in the Arctic. 

Three moorings (A2 and A4, in the eastern channel of Bering Strait, and A3, c.35nm north of Bering Strait), which were deployed from the Alpha Helix last year, were  recovered and redeployed.  All the moorings carry conventional instrumentation - current meters (RCM), temperature and salinity sensors (SBE16).   In addition, moorings A2 and A3 carry Upward-Looking-Sonars (ULS).  The new mooring A4 carries an upward-looking ADCP to study the coastal jet.  Mooring A3 also supports a nutrient sampler from UAF, and the replacement mooring carries in addition a transmissometer, a fluorometer and a PAR sensor, all connected to the SBE16.  The current meters and ULSes allow the quantification of the movement of ice and water through the strait.  The nutrient sampler and the optical sensors should yield the first biophysical time series measurements in the region, greatly advancing our understanding of the biological system in the Bering Strait and Chukchi Sea.

The second aim of the cruise was to conduct a hydrographic and ADCP survey of the Bering Strait and the southern part of the Chukchi Sea, concentrating on sections in the vicinity of the moorings and the region north of the mooring sites.  These CTD and nutrient measurements will be used to calibrate the moored instruments and to give a framework for the analysis of the data.  The hydrographic lines repeated and extended the surveys from previous years, allowing an interannual comparison.  

Our application to work in the Russian EEZ, submitted in December 2001, was turned down in June 2002.  Thus, all section and mooring work was confined to the US EEZ or international waters.

In addition to maintaining the time series measurements in Bering Strait, this work will also act as a upstream boundary condition for the NSF SBI (Shelf Basin Interaction) program, which starts its field work sampling this year.

 

CRUISE OBJECTIVES:

1.  To recover moorings A2-01, A3-01 and A4-01 (see Table 1).

2. To deploy moorings A2-02, A3-02 and A4-02.  As time/weather permits, to run hydrographic casts (CTD and nutrients) and ADCP sections in the vicinity of the moorings and in the southern region of the Chukchi Sea (see Table 2 and Figure 1).

 

Due to exceptionally good weather, all the cruise objectives were successfully accomplished.  The moorings were recovered and redeployed, and a total of 98 CTD stations, and corresponding ADCP lines were run.  Sampling details are provided below.

 

CRUISE SCHEDULE:

(Times are generally to the nearest half hour, and are in AKDS time, i.e. GMT-8hrs.  The map in Figure 1 gives the location of the CTD and ADCP lines.)

20th June 2002                 Join Alpha Helix at 9am, sail from Dutch Harbor at 1125

21st June 2002                 Transit to Bering Strait

                                         0705 Primary productivity station at site M2

22nd June 2002                Transit to Bering Strait

23rd June 2002                 Arrive Bering Strait at 1410

                                         1410 Primary Productivity Station at site A2

                                         1530-2100 CTD section along BS line

                                         2100-2400 ADCP section along BS line

24th June 2002                 0100-0400 ADCP section along MBS line

                                         0400-0830 CTD section along MBS line

                                         0900-1100 Recover and redeploy A4

                                         1200-1330 Recover and redeploy A2

                                         1730-1930 Recover and redeploy A3

                                         1930-0230 CTD section along A3L line

25th June 2002                 0230-1000 ADCP line along A3L line

                                         0947 Primary Productivity Station at site A3

                                         1500-0530 CTD and ADCP along PHL line

26th June 2002                 0530-1130 ADCP out to CCL line

                                         1130-2400 CTD section along CCL line, including

                                         1656 Primary Productivity Station at CCL15

27th June 2002                 0000-1000 ADCP section along CHUK and EEXT lines

                                         1000-2030 CTD section along EEXT and CHUK lines

                                         2030-0230 CTD section along CCL line (continued)

28th June 2002                 0230-0900 ADCP section along NBS line

                                         0900-1700 CTD section along NBS line

                                         1700-1930 CTD section along CCL line (continued)

                                         1930 Close of science, steam for Nome

29th June 2002                 arrive Nome ca.0700 and disembark

 

SAMPLING:

 

Due to the exceptionally good weather we encountered, we were able to complete the mooring work and an extended CTD and ADCP plan. 

 

Mooring Work:

All three moorings (see Table 1) were successfully and smoothly recovered and redeployed.  Releases functioned well.  All instrumentation was recovered in good condition.  Unlike in previous years (when mooring recoveries took place in the autumn), the moorings were not badly fouled and the rotors and salinity cells were reasonably clear of biological growth.

Of the three RCMs, two gave good data.  The third (A2) developed a battery short before deployment and recorded no data.  The three SBEs appear to have run well.  The ULSes were still working on recovery and binary data was successfully downloaded.  Although both records were complete, one ULS (A2) did not record any echo returns after January.  The nutrient analyzer ran for ca. 1 month before a mechanical plunger jammed.  (The unused chemicals from the analyzer were still in good condition after a year in the water.)

 

CTD and ADCP section work:

See Figure 1 and Table 2 for the CTD and ADCP sections ran.  A total of 98 CTD casts were taken.  (Three profiles were recast since the CTD acquisition software crashed part-way through the up-cast.)  Preliminary section plots are given in an Appendix.  Bottles were fired at standard depths (bottom, bottom-2m, 50m, 40m, 30m, 20m, 10m, 5m, surface) and samples were taken for nutrients, DMS, chlorophyll, O18 isotopes, nitrogen isotopes and salinity.  With the exception of the PHL and CCL lines, ADCP sections were run as dedicated sections at a speed of 7 knots.

 

Nutrient Analysis work (Whitledge, Thornton, Lee):

A total of 536 nutrient samples were taken and analyzed on board for silicate, phosphate, nitrate, nitrite and ammonia by Whitledge, Thornton and Lee.  Preliminary section plots are included as an appendix.  In addition, at many stations samples were taken at surface, mid water column and bottom for chlorophyll, and at some stations samples were taken for size-fractionated chlorophyll, fractionated on 20um, 5um and GF/F filters.  At the four sites M2, A2, A3 and CCL15, primary productivity stations (stable isotope nutrient enrichment primary productivity experiments with 15N-labeled nitrate and ammonia and 13C-labeled carbon) were also run.

 

DMS Analysis work (Deal):

DMS sea water profiles were taken at 18 stations, namely

June 23: A2-P

June 24: A4, A2, A3

June 25: PHL1, PHL6, PHL11

June 26: CCL12

June 27: EEXT3, CHUK10, CHUK7, CHUK2, CCL08

June 28: A3, NBS11, NBS7, NBS2, NBS1.

These samples were analyzed on board by Deal.

 

Oxygen isotope sampling (Woodgate for Cooper, Tennessee):

A total of 379 water samples were taken for O18 sampling.  Samples were taken at all stations except some of the productivity stations (see bottle list in an appendix).  These samples were sealed with parafilm and shipped to Lee Cooper at the University of Tennessee for later analysis.  To ensure the integrity of the bottle samples, when possible salinity samples (ca. 200) were taken from the bottles used for O18 samples.

 

Nitrogen Isotope sampling (by Deal for Tanaka, IARC/UAF)

Nine water samples (3 each at sites A2, A3 and A4) were taken for nitrogen isotope analysis.  These samples will be analysed post cruise by Dr Tomoyuki Tanaka, IARC/UAF. 

 

Underway sampling:

Seachest data showed evidence of some remarkable fronts during transit and in the work area.  For example, passing St Lawrence Island in the early evening, we encountered a few remaining small pieces of ice and a remarkably strong front in surface temperature and salinity.

The flow through Bering Strait was generally towards the south, reflecting the southward winds.  For the first few days in Bering Strait, the coastal jet was not easily identifiable (though a more comprehensive check of the ADCP data is required to confirm this).  For the latter part of the cruise, although the general flow was still southward, there did appear to be some evidence of the boundary current.

 

 

FIGURE 1: Overview Map of the Work Area

 

 


 

TABLE 1: Mooring Positions and Instrumentation

 

 

ID

LATITUDE (N)

LONGITUDE (W)

WATER DEPTH /m

INST.

 

 

 

 

 

Recovered

 

 

 

 

A2-01

65° 46.76'

168° 34.52'

56

ULS

 

 

 

 

RCM7

 

 

 

 

SBE16

 

 

 

 

 

A3-01

66° 19.58'

168° 58.03'

57

ULS

 

 

 

 

RCM9

 

 

 

 

SBE16

 

 

 

 

NAS-2E

 

 

 

 

 

A4-01

65° 44.73'

168° 15.83'

48

RCM7

 

 

 

 

SBE16

 

 

 

 

 

 

 

 

 

 

Deployed

 

 

 

 

A2-02

65° 46.77'

168° 34.53'

56

ULS

 

 

 

 

RCM7

 

 

 

 

SBE16

 

 

 

 

 

A3-02

66° 19.56'

168° 58.03'

57

ULS

 

 

 

 

RCM11

 

 

 

 

SBE+TF

 

 

 

 

NAS-2E

 

 

 

 

 

A4-02

65° 44.70'

168° 15.78'

49

ADCP

 

 

 

 

SBE16

 

 

 

ULS = APL Upward Looking Sonar

RCM7 = Aanderaa Mechanical Recording Current Meter

RCM9 = Aanderaa Acoustic Recording Current Meter

SBE16 = Seabird CTD recorder

SBE+TF = Seabird CTD recorder with transmissometer, fluorometer and PAR sensor

NAS-2 = Nutrient Analyzer

ADCP = RDI Acoustic Doppler Current Profiler

TABLE 2: CTD Positions

 

Name           #     Time (GMT)         Stat         Lat(N)      Long(W)     D    P-   P+

hx2600001   1  Jun 21 2002 15:05  m2           57  5.83   165  5.22     72  3.1 69.8

hx2600002   2  Jun 23 2002 22:13  a2p          65 45.80  168 34.09     57  2.2 52.2

hx2600003   3  Jun 23 2002 23:42  bsl6         65 40.93  168 10.89     26  1.6 28.3

hx2600004   4  Jun 24 2002 00:17  bsl5         65 41.37  168 15.22     42  2.0 45.1

hx2600005   5  Jun 24 2002 00:46  bsl5         65 41.78  168 19.52     51  2.5 53.7

hx2600006   6  Jun 24 2002 01:23  bsl4.5      65 42.15  168 24.01     54  1.1 51.3

hx2600007   7  Jun 24 2002 01:49  bsl4         65 42.62  168 28.20     51  2.2 52.5

hx2600008   8  Jun 24 2002 02:18  bsl3.5      65 43.05  168 32.38     54  1.9 54.8

hx2600009   9  Jun 24 2002 02:46  bsl3         65 43.50  168 36.98     54  1.4 51.0

hx2600010  10  Jun 24 2002 03:22  bsl2.5     65 43.72  168 40.86     50  1.7 51.4

hx2600011  11  Jun 24 2002 03:46  bsl2        65 44.12  168 45.04     50  2.2 52.8

hx2600012  12  Jun 24 2002 04:19  bsl1.5     65 44.75  168 48.65     50  1.9 52.6

hx2600013  13  Jun 24 2002 04:45  bsl1        65 45.49  168 52.12     40  2.2 42.6

hx2600014  14  Jun 24 2002 12:03  mbs1      65 52.09  168 57.04     43  2.0 41.8

hx2600015  15  Jun 24 2002 12:40  mbs2      65 51.88  168 49.05     50  2.1 50.3

hx2600016  16  Jun 24 2002 13:14  mbs3      65 51.69  168 40.94     51  2.1 51.4

hx2600017  17  Jun 24 2002 13:48  mbs4      65 51.55  168 31.92     55  1.9 51.8

hx2600019  19  Jun 24 2002 14:37  mbs5      65 51.37  168 23.01     50  2.2 51.3

hx2600020  20  Jun 24 2002 15:13  mbs6      65 51.13  168 13.92     50  2.3 46.7

hx2600021  21  Jun 24 2002 15:45  mbs7      65 50.96  168  6.93      40  2.3 38.5

hx2600022  22  Jun 24 2002 16:05  mbs8      65 50.93  168  5.04      32  2.6 30.7

hx2600023  23  Jun 24 2002 17:44  a4-01      65 44.68  168 15.94     45  2.1 46.5

hx2600024  24  Jun 24 2002 20:49  a4           65 46.74  168 34.36     54  2.1 53.8

hx2600025  25  Jun 25 2002 02:18  a3           66 19.58  168 58.18     54  2.5 53.4

hx2600026  26  Jun 25 2002 04:14  A3L2       66 21.26  168 48.38     57  2.5 53.6

hx2600027  27  Jun 25 2002 04:49  A3L3       66 22.75  168 39.81     59  2.4 55.5

hx2600028  28  Jun 25 2002 05:31  A3l4        66 24.13  168 30.22     55  2.0 52.1

hx2600029  29  Jun 25 2002 06:35  A3L5       66 25.89  168 18.67     50  2.4 47.1

hx2600030  30  Jun 25 2002 07:16  A3L6       66 28.09  168  6.35      30  2.4 27.7

hx2600031  31  Jun 25 2002 07:51  A3L7       66 29.71  167 56.77     25  2.7 22.5

hx2600032  32  Jun 25 2002 08:32  A3L8       66 31.71  167 42.82     27  2.6 25.0

hx2600033  33  Jun 25 2002 09:25  A3L9       66 34.75  167 25.32     32  2.2 29.7

hx2600034  34  Jun 25 2002 10:13  A3L10     66 37.41  167  9.23      35  2.6 30.5

hx2600035  35  Jun 25 2002 17:51  a3lp        66 20.17  168 56.15      54  2.2 53.8

hx2600036  36  Jun 25 2002 23:19  phl1        67 11.04  168 11.90      36  2.1 36.7

hx2600037  37  Jun 26 2002 00:14  phl2        67 18.07  168 14.93      45  2.1 42.2

hx2600038  38  Jun 26 2002 01:34  phl3        67 30.08  168 18.93      50  2.2 45.9

hx2600039  39  Jun 26 2002 03:21  PHL4      67 45.60  168 23.69      53  2.4 47.6

hx2600040  40  Jun 26 2002 04:18  PHL5      67 51.02  168 24.95      54  2.5 50.8

hx2600041  41  Jun 26 2002 05:30  phl6        67 57.13  168 28.16      60  2.2 56.6

hx2600042  42  Jun 26 2002 06:38  phl7        68  0.15  168 14.05       60  2.3 56.5

hx2600043  43  Jun 26 2002 07:42  PHL8      68  3.55  168  0.05        58  2.6 53.9

hx2600044  44  Jun 26 2002 08:51  phl9        68  7.05  167 47.04       55  2.3 51.8

hx2600045  45  Jun 26 2002 09:55  PHL10    68 10.48  167 33.54      51  2.2 48.0

hx2600046  46  Jun 26 2002 11:05  PHL11    68 14.02  167 17.98      48  2.3 44.7

hx2600047  47  Jun 26 2002 12:10  PHL12    68 17.06  167  3.11       41  2.3 37.0

hx2600048  48  Jun 26 2002 13:07  PHL13    68 19.03  166 50.69      31  2.5 27.6

hx2600049  49  Jun 26 2002 19:33  ccl19       68 29.98  168 56.98     55  2.1 51.5

hx2600050  50  Jun 26 2002 20:49  ccl18     68 19.99  168 56.95       55  1.7 53.3

hx2600051  51  Jun 26 2002 22:05  ccl17      68 10.05  168 56.88      58  2.8 56.4

hx2600052  52  Jun 26 2002 23:20  ccl16      67 59.97  168 56.97      62  3.0 57.0

hx2600053  53  Jun 27 2002 00:34  ccl15      67 49.98  168 56.78      53  2.3 50.1

hx2600054  54  Jun 27 2002 00:56  ccl15P    67 50.06  168 57.16     53  2.3 42.4

hx2600055  55  Jun 27 2002 02:08  ccl14       67 40.03  168 56.75     53  2.3 48.5

hx2600056  56  Jun 27 2002 03:17  ccl13       67 29.99  168 57.10     52  2.7 48.1

hx2600057  57  Jun 27 2002 04:24  CCL12    67 19.99  168 57.17     51  2.4 47.4

hx2600058  58  Jun 27 2002 05:34  CCL11    67  9.96  168 57.07      50  2.3 46.7

hx2600059  59  Jun 27 2002 06:46  CCL10    66 60.00  168 56.98     50  2.4 45.9

hx2600060  60  Jun 27 2002 08:04  CHUK1   66 48.93  168 58.30     44  2.0 42.7

hx2600061  61  Jun 27 2002 18:08  EEXT3    66 34.97  166 11.91     15  1.9 13.2

hx2600062  62  Jun 27 2002 19:14  EEXT2    66 36.64  166 33.82     26  2.4 20.7

hx2600063  63  Jun 27 2002 19:51  EEXT1    66 37.52  166 43.74     30  1.4 29.0

hx2600064  64  Jun 27 2002 20:52  chuk10    66 38.89  167  0.95      35  1.6 31.0

hx2600066  66  Jun 27 2002 21:52  chuk9      66 39.94  167 10.55     32  1.9 31.9

hx2600067  67  Jun 27 2002 22:52  chuk8      66 41.41  167 27.99     30  1.7 30.3

hx2600068  68  Jun 27 2002 23:53  chuk7      66 42.88  167 46.00     27  2.0 28.7

hx2600069  69  Jun 28 2002 00:37  chuk6      66 43.81  167 57.05     28  1.5 28.6

hx2600070  70  Jun 28 2002 01:17  chuk5      66 44.82  168  8.01      31  1.9 29.2

hx2600071  71  Jun 28 2002 02:04  chuk4      66 45.86  168 22.01     34  1.6 30.7

hx2600072  72  Jun 28 2002 02:45  chuk3      66 46.86  168 34.11     34  2.5 30.6

hx2600073  73  Jun 28 2002 03:27  chuk2      66 47.87  168 46.00     44  2.1 39.3

hx2600074  74  Jun 28 2002 04:16  chuk1      66 48.86  168 58.19     48  3.0 44.5

hx2600075  75  Jun 28 2002 05:25  CCL08    66 39.00  168 57.10     46  2.5 41.4

hx2600076  76  Jun 28 2002 05:53  CCL07    66 36.03  168 57.21     48  2.1 44.1

hx2600077  77  Jun 28 2002 06:46  CCL06    66 28.95  168 57.15     58  2.0 55.7

hx2600078  78  Jun 28 2002 07:54  A3           66 19.40  168 58.22     58  2.7 55.4

hx2600079  79  Jun 28 2002 09:03  CCL4      66 10.04  168 57.16     58  1.8 54.4

hx2600080  80  Jun 28 2002 10:16  NBS1      65 59.96  168 58.15     55  2.6 51.6

hx2600081  81  Jun 28 2002 16:55  nbs14     65 59.97  167 10.16     10  0.9  7.4

hx2600082  82  Jun 28 2002 17:24  nbs13     65 59.93  167 18.13     13  2.5 10.9

hx2600083  83  Jun 28 2002 17:58  nbs12     65 59.94  167 29.10     18  2.4 15.1

hx2600084  84  Jun 28 2002 18:34  nbs11     65 59.92  167 40.12     15  2.1 15.0

hx2600085  84  Jun 28 2002 19:24  nbs10     66  0.03  167 51.99      12  1.0  9.4

hx2600086  86  Jun 28 2002 19:40  nbs9       65 59.98  167 55.11     20  1.9 19.3

hx2600087  87  Jun 28 2002 20:02  nbs8       65 60.00  167 59.94     34  2.2 32.6

hx2600088  88  Jun 28 2002 20:35  nbs7       65 59.97  168  8.36      45  3.1 47.8

hx2600090  90  Jun 28 2002 21:28  nbs6       65 59.99  168 16.43     50  2.2 53.5

hx2600091  91  Jun 28 2002 22:08  nbs5       65 59.98  168 25.03     55  2.0 56.9

hx2600092  92  Jun 28 2002 22:51  nbs4       66  0.02  168 33.16      52  2.3 54.7

hx2600093  93  Jun 28 2002 23:33  nbs3       65 59.96  168 41.57     52  2.8 52.5

hx2600094  94  Jun 29 2002 00:10  nbs2       65 59.97  168 49.88     52  2.6 52.9

hx2600095  95  Jun 29 2002 00:47  nbs1       65 59.97  168 58.13     51  1.7 51.8

hx2600096  96  Jun 29 2002 01:49  mbs1      65 52.17  168 57.18     42  2.2 43.9

hx2600097  97  Jun 29 2002 02:33  LD-1       65 47.03  168 57.06     36  1.9 32.5

hx2600098  98  Jun 29 2002 03:11  BSL1      65 45.54  168 52.30     46  2.2 41.4

 

(D = approximate water depth in m)

(P-, P+ = min/max pressure of CTD in dbar)