|Recovery of BPR (Bottom Pressure Recorder) originally installed at Axial in 2013.|
By Rachel Teasdale
Weather: Overcast skies and moderately strong winds of about 25 knots (29 mph), with gusts up to 35 knots (40 mph); waves are 4-6 feet with swells up to 12 feet.
What’s happening today? The weather is keeping us from launching Jason and Sentry again today, so we did a midnight CTD launch and are continuing to recover and deploy seafloor instruments (OBHs – ocean bottom hydrophones and BPRs – bottom pressure recorders). We’ll do another CTD tow-yo later this evening.
As noted in previous entries, the winds have picked up and the seas have been rough, which continues to prevent the launch of the ROV Jason and AUV Sentry. Vehicle launches and recoveries require the Sentry- and Jason- group team members and numerous ship’s crew to work on the deck of the ship as cranes lift vehicles overhead while the ship is heaved up and down with the waves. In bad weather, the vehicles could potentially swing and collide with the ship, other equipment or personnel. The waves do not affect the AUV Sentry while it is in the sea, but it must be recovered within the lifespan of the batteries, so launches must be made when the window of weather is certain to allow a timely and safe recovery. The ROV Jason and Medea are tethered to the ship with a fiber-optic cable so can remain submerged for long periods of time, but large motions of the ship can cause the cable to yank on Medea which could damage the cable. Thus, the potential for damage or injury makes it not possible to use these vehicles during heavy weather.
One of Chief Scientist Bill Chadwick’s many responsibilities is scheduling the individual activities of the cruise, including each of the ROV Jason and AUV Sentry dives, installation and recovery of instruments, and CTD casts. Chadwick is revising the cruise plan to maximize the research that can be accomplished during the cruise in spite of the weather. In lieu of vehicle dives, the science plan during the last few days has been altered from predominantly dive-focused work, to activities that focus on other aspects of the cruise plan. The last few days we have been able to launch and recover OBH and BPR instruments that are used in the geophysical monitoring of Axial Seamount (image above).
|Emily Reddington, Chris Algar and Dave Butterfield prepare instruments for collecting vent water samples.|
Microbiologist Chris Algar has been collecting CTD water samples and will measure the activity of the microbe communities that live in the vents. Unlike humans who breathe O2, autotrophic vent microbes respire hydrogen (H2) that is concentrated in vent fluids, producing methane (CH4) as a byproduct. The vent microbes incorporate CO2 to make their biomass, so to compare the activity of the vent microbes Chris measures the rate at which CO2 is taken up at each vent site and can also compare that activity with the carbon uptake in non-vent sea water. Ultimately, Chris’ work can be used to help quantify the role that microbe communities in vent fluids play in the ocean’s carbon cycle.
|AUV Sentry engineers Loral O’Hara (left) prepares launch and recovery plans as Stefano Suman processes sonar data.|
Engineer Zach Berkowitz is busy fine-tuning upgraded vehicle systems for the next deployment of AUV Sentry and Stefano Suman is testing a new data processing technique for the sonar data collected by AUV Sentry on August 16 to compare new and existing methods for creating the seafloor maps. Justin Fujii and Loral O’Hara are looking ahead and developing launch and recovery methods for a future cruise (see image above).