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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.
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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.
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STATION
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DATE |
MAP |
TIME(UTC) |
LATITUDE |
LONGITUDE |
TARGET
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DURATION |
REMARKS |
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05/08/02
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1900
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64.96N
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169.14W |
50m |
12.5
hrs |
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