flexe: From Local to Extreme Environments

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Dataset 2: Vent Fluid Temperature over Time

Hello FLEXE Students! I'm Dr. Karen Von Damm. I am a chemical oceanographer and professor at the University of New Hampshire. It's nice to be working with you.

I study the hydrothermal vents found all along the mid-ocean ridge system. While I have worked in the Atlantic and Indian Oceans, and at other ridges in the Pacific, I have worked mostly on the East Pacific Rise (9°03'N 104°18'W). When you add up all of my cruises, I have spent more than two years of my life at sea, and about 2 months of that time on the bottom of it.

Hydrothermal vents are fascinating and complex systems. Here's a video clip of a vent pumping out extremely hot fluid. The video also shows a special probe placed into the fluid to measure its temperature. I am interested in understanding what's in the fluid jetting out of these vents and how it came to be. Even though it looks like smoke, it's actually more like steam. The chemistry of the vent fluids can tell us a lot about the history of what happened to the seawater as it traveled through the oceanic crust. And to understand the chemical reactions taking place, we need to know the temperature. For a simple overview of this process, visit the Dive and Discover website on chimney chemistry.

I've been studying the chimneys in this area for several years now, since 1991 in fact. Just like your studies in your own environment, one of the important environmental parameters I measure at the vents is temperature. Temperature is not as easy for us to measure in a hydrothermal vent on the seafloor as it is in your environment on land. One of the challenges is getting to our study site - it is expensive and time consuming to travel there. Also, long-term studies of continuous temperature measurements require special probes that can collect and store data under extreme conditions. The dataset listed below was collected using these special probes, called HOBO probes. Each probe consists of a thermocouple with a battery-powered data logging device housed in a titanium pressure housing. You may have a similar data logger at your school, although yours don't have to be as tough as the deep-sea HOBO! To deploy the probe, the robotic arm of a submersible places the HOBO probe in the flow of fluid near the opening of a chimney, just where the fluid exits. The probe is programmed to read and record temperature at regular intervals for a year. When the probe is retrieved, we typically leave a new probe behind. Data from multiple probes are then compiled into one dataset.

We used one of these compiled datasets to create a graph showing HOBO temperature measurements of a well-known chimney called "Bio9" so named because of its proximity to a seafloor marker named "Biomarker #9". In 1992, we placed over 200 markers in this area to study the changes in this area over time. "Bio9" is located at 9°50.2'N 104°17.5'W. As you see in the graph, temperature measurements were collected for several years.

One of the questions we've been trying to answer is "How does vent fluid temperature change over time?" Take a look at this graph of temperature readings and see if you can detect a pattern. Use the graph to help you think about the data and to answer the questions on the handout provided by your teacher. Once you've completed the handout, return to the Forum and answer the questions we've posted. We look forward to hearing what you think.