Final Cruise Report: Western Arctic Shelf-Basin Interactions (SBI) Spring Cruise HLY-02-01

(5 May-15 June 2002)

 

Edited by Jackie Grebmeier, Chief Scientist

University of Tennessee, Knoxville, TN 37922 USA

email: jgrebmei@utk.edu

 

A.  Introduction

 

The field phase of the Western Arctic Shelf-Basin Interactions (SBI) project completed a successful scientific mission to the Arctic on the new USCGC Healy icebreaker 5 May -15 June 2002. This was the first interdisciplinary research cruise to this region by a science vessel at this time of year. About a dozen interdisciplinary research projects were included in the ship-based program, ranging from hydrographic measurements to biological studies of various trophic levels. The goal of the SBI global change project is to investigate the production, transformation and fate of carbon at the shelf-slope interface in the Arctic as a prelude to understanding the impacts of a potential warming of the Arctic. Thirty-nine stations were occupied in the northern Bering Sea (test station), the Chukchi Sea shelf (Herald Valley [HV] transect), the Chukchi outer shelf to Arctic Basin lines (West Hanna Shoal [WHS] and East Hanna Shoal [EHS] transect lines), stations near Pt. Barrow, and the Barrow Canyon (BC) transect (Figure 1). Some regions in the study area had lighter ice cover than expected, although normal heavy ice limited sampling in the northwest region of the Chukchi Sea and the eastern most line in the Beaufort Sea.

 

The SBI project is an interdisciplinary program, where physical, biogeochemical and biological measurements were made using a variety of sampling devices. CTD/rosette sampling collected physical and hydrochemical samples. Subsamples from four CTD/rosette casts were used for primary production, chlorophyll content, nutrients, particulate carbon, inorganic carbon, biomarkers, microzooplankton, and radioisotopes. Various nets (vertical, bongo) were used to collect size fractions of micro-macro- and meso-zooplankton for both population and experimental purposes. Benthic grabs and cores were used to collect benthic fauna and sediment samples for population, community structure, food web and metabolism studies. Off-ship sampling by lowering personnel to the ice occurred to undertake ice measurements and to collect ice cores. Shipboard marine mammal surveys from the bridge were undertaken by the US Fish and Wildlife Service (USFWS). Limited helicopter operations were used for ice reconnaissance, during which marine mammal imagery was possible during two sorties.

 

During the cruise the Joint Office of Science Support (JOSS) group of the University Corporation for Atmospheric Research group maintained a shipboard field catalog that provided real-time data to scientists on the ship and allowed them to track ship and station progress during the cruise. It also assisted the scientists in providing access to the service group datasets and preliminary analyses and acted as an instrument whereby scientists could share their observations and preliminary analyses. The catalog also allowed onshore PIs to follow the progress of the cruise and a limited number of products were mirrored back to a JOSS SBI catalog running in Boulder, Colorado. The SBI field catalog (with maps and event information at sea) can be found on the webpage: (http://www.joss.ucar.edu/sbi/catalog/). Full details on the SBI project, the field cruise program and results to date can be found on the SBI webpage http://utk-biogw.bio.utk.edu/SBI.nsf and associated links on that web site. In particular, a highlight summary taken from the PI findings for the spring SBI cruise can be found on the SBI and JOSS webpages.

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1. Station location and cruise track for the spring SBI cruise on the USCGC Healy (HLY-02-01).

 

B. Cruise Overview and Issues

The cruise initiated in Nome, Alaska, had a test station in the northern Bering Sea, sailed through western Bering Strait and transited NW along the international dateline to the 100 m isobath of NW Chukchi Sea. This entry date and direction into the study region resulted from discussions with the Alaska Eskimo Whaling Commission (AEWC), who were concerned about our transiting through eastern Bering Strait and along the coastline during the spring bowhead whale migration. Despite efforts at communication between groups in Alaska and the SBI management, concerns continued to just before the cruise, specifically related to the timing of the project in May during the spring bowhead whale migration. As part of the resolution, the AEWC was kept informed of our research progress, which was fully available on the JOSS web site, including an updated station location map.

During the cruise, ice conditions were the main limiting factor for not completing two of the 5 transect lines outlined in the HLY-02-01 cruise plan. Heavy ice on the outer Herald Valley line in the Chukchi Sea, slow travel time around a major flow west of Barrow, and heavy ice over the East Barrow line inhibited our working these transect lines. It is estimated 2 days of ship time were lost due to ice-related delays in transit to specific science areas.

The other major limiting factor on the success of the mission was lack of ambient seawater from the start of the cruise. In spite of both scientist and Healy engineering efforts, it took weeks after the cruise started to find a satisfactory resolution of obtaining and maintaining ambient seawater flow for deck-board incubations. An initial NSF-supported refrigerated van system with recirculating pumps and storage tanks was unable to maintain ambient seawater temperatures. The ultimate resolution was provided by the USCG engineering division so that the ship connected a ballast water tank to the bow incubators through a system for providing 7 hose connections to the incubators. When the seawater in the ballast tank warmed up, science requested a dumping of the water in transit and a subsequent refill on station, which occurred using air operated pumps (AOPs) provided by the USCG. The positive attitude of the USCG in resolving this situation and collaboration between science and USCG enabled a viable resolution to the ambient seawater needs of the primary production and zooplankton groups. It should be noted that there was steady heating of the ballast seawater over the daily warming cycle, especially under clear skies. It was during such good weather that the “dump and pump” technique was most used. Further information on the ambient seawater bow system can be viewed in Appendix A. It should be noted that although it was speculated that these daily temperature swings in the deck incubators would be major problem for the summer SBI cruise, this has not occurred. Subsequent to the end of the spring SBI cruise the Engineering Officer, Neil Meister, had a second 7-hose connector system built and installed for delivering ambient seawater to both sides of the ship, which resulted in sufficient flow to maintain ambient seawater during the summer cruise most of the time.

The Captain, officers and crew of the USCGC Healy were very professional and helpful, being essential to the success of the cruise goals. We appreciated the continued, professional support provided by Captain David Visneski, Operations Officer Joe Segalla, Executive Officer Doug Russell, Engineering Officer Neil Meister, and Master Chief Navigator George Schwarz. Valuable support for science was provided by the lead Marine Science Technician Glen Hendrickson, and the other Marine Science Technicians (Sean Kuhn, Suzanne Scriven, Bridget Cullers, and Michael Hamerski), along with the Science Officer Mike Woodrum. The Aviation Detachment under the direction of Mike Platt provided essential logistical support for ice surveys and limited science operations. SBI land logistical support was ably provided by Andy Heiberg of the University of Washington.

C. Summary of Science Reports

Stations occupied during HLY-02-01 were in the northern Bering Sea (test station), the Chukchi Sea shelf (HV transect), the Chukchi outer shelf to Arctic Basin lines (West Hanna Shoal: WHS transect), stations near Pt. Barrow, and the Barrow Canyon (BC) line. Table 1 provides a general summary of station location, target depth, station duration, Note that there is an interactive table with links to station maps and event logs for each station on the JOSS SBI webpage (http://www.joss.ucar.edu/sbi/catalog/).

The following science summaries include sampling collection information and preliminary findings. In addition, three appendices are attached: Appendix 1 is a summary of ballast tank information; Appendix 2 is the final service team hydrographic report, and Appendix 3a and 3b are the ADCP reports. All appendices, and a highlights summary (based on the current cruise report) can be found on the JOSS webpage: http://www.joss.ucar.edu/sbi/catalog - JOSS SBI Field Catalog.


Table 1. Station summary for the spring SBI cruise HLY-02-01.

STATION
NO.

DATE

MAP

TIME(UTC)

LATITUDE

LONGITUDE

TARGET
DEPTH

DURATION
(HRS)

REMARKS

HLY-02-01-000

05/08/02

MAP

1900

64.96N

169.14W

50m

12.5 hrs

Event Log

HLY-02-01-001