Dr. Joe Resing standing next to the scanner used to perform continuous chemical analysis while in the water column. Chemist Ron Greene is carefully extracting a water sample to analyzed for helium.

Teacher Logbook - R/V Wecoma

Missy Holzer 's Sealog:
CTD Cruise Day 10
Weather at 1630 hours PDT:
Overcast skies with winds of 12 knots from the northwest, and visibility of 12 miles. Barometric pressure is 1026.9, and the temperature is 58 degrees Fahrenheit. Ocean swells are 5 feet out of the northwest, and the seas are 6 feet out of the northwest.

Hard to believe that we've spent over a week sampling the water column above Axial volcano and now it's time to move onto our next location on the Juan de Fuca Ridge. This evening the NeMO CTD cruise will be steaming to the Cleft segment of the ridge located about 60 miles south of our current location. The Cleft segment of the Juan de Fuca Ridge is one the 3 most active segments of the ridge along with the Axial and Endeavor segments, and has been monitored by the Hydrothermal Plume Studies Group since 1986. Similar sampling will take place at Cleft that has taken place at Axial: CTD casts and tow-yo's.

During our week at Axial, we completed 8 tow-yo's and 26 casts, along with recovering 5 and deploying 4 moorings. Within the casts and tow-yo's some interesting chemistry techniques were in operation. A "scanner" as Dr. Joe Resing calls it was used to do real-time chemical analysis while in the water column. The apparatus appears to be pretty fragile with tubes, and bags hanging loosely from its frame, but somehow the chemical reactions take place every 5 seconds. Once the fish and the scanner have been recovered Dr. Resing hooks up the scanner to a computer to gather the data about the presence of iron and manganese in the vicinity of Axial volcano. Although his predecessor developed the scanner, Dr. Resing has made some modifications that a longer time series of data may be acquired.

Helium in water? Isn't helium a gas? Well, helium like other gases can be trapped in the ocean water (think of all the gas in a bottle of soda). Helium, like other elements found on the periodic table, can be found in various forms in nature. These other forms of the elements are called isotopes and some of them are a bit more stable than other forms, or in the case of helium, both are stable. In ocean water, a version of helium called Helium-4 is about a million times more common than a version called Helium-3, although both will rise in quantity after a hydrothermal activity. Chemist Ron Greene has adopted an interesting method of extracting and analyzing the quantity of helium present in the water column by using an air-tight system involving cold welding of copper piping. He gathers samples from approximately 5 Nisken bottles from each tow and cast. These prepared samples are taken back to his lab in PMEL NOAA lab in Newport, OR where he uses mass spectrometry to acquire the final ratios of Helium 3 to Helium 4 in each of the samples. What he has found from the data is that since the 1998 eruption at Axial volcano, the helium signal has decreased due to less helium being ejected in the plume sites. So long as the plumes are somewhat active there will be a helium signal to monitor.

Work continues as the NeMO CTD Cruise moves on to our next location. Come back on line to check the status of our research at Cleft segment.