USCGC Healy Cruise HLY-1502
US Arctic Geotraces
Weekly CTD/Hydrographic Team Report 01
from Jim Swift, UCSD/SIO, CTD/hydro team scientific leader at sea

Sunday, 16 August 2015, 6:45 pm, local date and time (0245 17 August UTC)

68°N, 168°W (in the Chukchi Sea, about 100 miles north of Bering Strait)
air 7.8 degC / 46 degF
water 5.7 degC / 42 degF
wind 15 knots from NNE

On Station 6

Note: This is a hydrography-oriented report from Jim Swift, who is working with the SIO Oceanographic Data Facility (ODF) CTD/hydrographic team on the US Geotraces Arctic Ocean expedition led by Dr. David Kadko, FIU, chief scientist. This is not a report from Dr. Kadko or the other science teams.

US Coast Guard science icebreaker Healy left Dutch Harbor, AK, on schedule at 1300 local time on 09 August, one week ago, bound for the Arctic Ocean. The SIO/ODF team had loaded its equipment in Seattle in June, but the routine chemistry equipment (for analysis of bottle salinity, dissolved oxygen, and nutrients) needed to be set up in Dutch Harbor because the science team on HLY-1501 was using the designated lab space. The data processing computers were installed, and the CTD/rosette systems also needed final set up and checking. The set ups, chemical preparations, and tests went smoothly.

ODF is using two rosette systems on this cruise: a 12-place system equipped with 30-liter bottles, used to support Geotraces, and a 36-place system equipped with 10-liter bottles, which will be used to support extra CTD stations along the US Geotraces track in support of the US Global Ocean Carbon and Repeat Hydrography program. [There is also a third rosette system in use - Greg Cutter’s (ODU) trace metal clean system.] These two large rosettes share the Healy’s starboard staging bay and though we use one at a time, they use the same winch, sheave and CTD cable. Switching from one to the other is not trivial, so we plan to use only one of the systems at any given station, switching in between stations. [That sounds fine, but CTD aficionados will know this invites gremlins. Time will tell.] We plan to use the 12x30 system for the first 11 stations, so we tested the 36x10 system in water at the dock, then moved the 12x30 system into cast operation position. The CTDs in both units are working well. The 30-liter bottles are touchy in terms of leaks. (There are ca. 65 lbs of water pushing at the bottom end caps, held tight onto an O-ring by a strong spring in the bottle.) The techs have been working out the kinks and we are satisfied with progress. [One way we stop a leak is to hit the bottom end cap with a non-metallic mallet (see photo, taken by Joseph Gum, SIO, showing oxygen sampler Andrew Barna and hammer-wielder Melissa Miller of SIO). Yes, using a hammer is still how some equipment is fixed!]

The quality of the ODF CTD and bottle data is excellent. The CFC/SF6 team (LDEO and UofHawaii) on board reports their sample analysis equipment is working reasonably well, with a few of the usual bugs. The ocean carbon team (UofMiami) has been generating good data, but their lab van has been overheating. Their analysis equipment generates appreciable heat, but needs a stable lab temperature for best performance. They have a fine air conditioning system but the ship cannot connect it, and so they must attempt to cool the van by leaving a van door part-way open to the cold outside air. This requires that they use headlamps in their van at night (even though we are well north we currently still have a dark period) because their van is in front of the bridge, and the normal lab lights shining out the open door would affect the vision of personnel on the bridge. There is attention being paid to this issue, and progress may lie ahead.

Most of the stations to date have been shallow shelf stations (50 meters or less), and the hydrographic structures of the shelf waters are as one would expect: summer waters on top of winter waters, and, at station 001, which was just off the Bering Sea shelf, a transition to cold, low-salinity, low oxygen, high nutrient Bering Sea waters.

Within the next week we will carry out a section off the shelf. The chief scientist may choose to run the planned track in reverse, in order to take advantage of present and predicted August-September ice conditions over the planned track as a whole.

All is well.